This PDF file contains the front matter associated with SPIE Proceedings Volume 10453, including the Title Page, Copyright information, Table of Contents, and Conference Committee listing.

We study the interaction properties of two-channel wavelength-division multiplexed strongly dispersion managed communication systems. By means of a variational approach to the Generalized Nonlinear Schrödinger Equation we obtain an ordinary differential equations model for the main parameters of the pulses including third-order dispersion, Raman scattering and self-steepening. We study the residual frequency shift for each channel after the collision between sets of two pulses as a function of the ratio of dissimilar peak powers in a broad range of dispersion difference values, concluding that the transmission characteristics improve by using specific values of unequal energies and considering higher-order correction terms.

Microtopographic and rugometric characterization of surfaces is routinely and effectively performed non-invasively by a number of different optical methods. Rough surfaces are also inspected using optical profilometers and microtopographer. The characterization of road asphalt pavement surfaces produced in different ways and compositions is fundamental for economical and safety reasons. Having complex structures, including topographically with different ranges of form error and roughness, the inspection of asphalt pavement surfaces is difficult to perform non-invasively. In this communication we will report on the optical non-contact rugometric characterization of the surface of different types of road pavements performed at the Microtopography Laboratory of the Physics Department of the University of Minho.

Malaria is a parasitic disease with more than a billion people worldwide at risk of contraction. The disease is predominantly widespread in regions with precarious healthcare conditions and resources. Despite the several available malaria diagnostic methods, only two are predominantly used in the field in malaria-endemic countries: microscopy and rapid diagnostic tests. In this work, an alternative diagnostic system is proposed, based on optical absorption spectrophotometry. The main objective of this paper is the spectrophotometric study of hemozoin as a malaria biomarker, since it is a sub-product of the malaria infection. The optical absorbance of hemoglobin and hemozoin solutions in purified water was measured in the visible spectrum range using a spectrophotometric setup. The results showed main absorbance peaks at 540 nm and 574 nm for hemoglobin, and at 672 nm for hemozoin. The tests performed in aqueous solutions have shown that both hemoglobin and synthetic hemozoin, when alone in solution, were detected by absorbance, with sensitivity of 0.05 g/L, and with a high linearity (R²> 0.92 for all wavelength peaks). Furthermore, it was found that the whole blood and the hemoglobin spectra have similar absorption peaks. By combining whole blood and synthetic hemozoin solutions, it was proved that both the hemozoin and the hemoglobin absorbance peaks could still be detected by spectrophotometry. For instance, in polydimethylsiloxane wells, the proposed method was able to detect hemozoin in whole blood samples for optical paths as low as 3 mm in cylindrical wells, thus proving the capability for this method’s miniaturization. With this work, it is possible to conclude that hemozoin is a viable candidate as a biomarker for malaria detection by optical absorption spectrophotometry and also, that an autonomous, fully integrated and low cost miniaturized system, based on such a principle, could provide an efficient diagnosis of malaria.

Ellipsometry is an optical technique to characterize materials or phenomena that occurs at an interface or thin film between two different media. In this paper, we present an experimental low-cost version of a photometric ellipsometer, assembled with commonly found material at every Optics laboratory. The polarization parameters measurement was performed using a Thorlabs PAX5710 polarimeter. The uncertainty computed using the Guide to the Expression of Uncertainty in Measurement (GUM) procedures. With the assembled ellipsometer we were able to measure the thickness of a 10 nm thick SiO₂ thin film deposited upon Si, and the complex refractive index of Gold and Tantalum samples. The SiO₂ thickness we achieved had an experimental deviation of 4.5% with 2.00 nm uncertainty. The value complex refractive index of Gold and Tantalum measured agrees with the different values found in several references. The uncertainty values were found to be mostly limited by the polarimeter’s uncertainty.

We have successfully generated a new broadband coherent light source in the continuous wave (CW) regime which is an ensemble of multi-harmonic radiations (2403, 1201, 801, 600 and 480 nm) by implementing a frequency dividing technology. The system is uniquely designed that all the harmonics are generated and propagate coaxially which gives the advantage of robustly maintaining the phase coherence among the harmonics. The highlight is its huge potential for the arbitrary optical waveform synthesis in the CW regime which has not been performed yet due to the limitation of the existing light source.

Resonant tunneling diodes (RTDs) have been extensively studied due to their potential applications in very high speed electronics, optical communications, and terahertz generation. In this work, we report the latest results on the characterization of the resonant tunneling diode photo-detectors (RTD-PDs), incorporating InGaAlAs light sensitive layers for sensing at the telecommunication wavelength of λ = 1310 nm. We have measured responsivities up to 28.8 A/W and light induced voltage shift of 204.8 V/W for light injection powers around 0.25 mW.

Resonant tunneling diodes (RTDs) are the fastest pure electronic semiconductor devices at room temperature. When integrated with optoelectronic devices they can give rise to new devices with novel functionalities due to their highly nonlinear properties and electrical gain, with potential applications in future ultra-wide-band communication systems (see e.g. EU H2020 iBROW Project). The recent coverage on these devices led to the need to have appropriated simulation tools. In this work, we present RTD based optoelectronic circuits simulation packages to provide circuit signal level analysis such as transient and frequency responses. We will present and discuss the models, and evaluate the simulation packages.

In this paper we present a MUX/DEMUX device based on a multilayer a-SiC:H optical filter that requires nearultraviolet steady state optical switches to select desired wavelengths in the visible range. Spectral response and transmittance measurements are presented and show the feasibility of tailoring the wavelength and bandwidth of a polychromatic mixture of different wavelengths.

The selector filter is realized by using a two terminal double pi’n/pin a-SiC:H photodetector. Five visible communication channels are transmitted together, each one with a specific bit sequence. The combined optical signal is analyzed by reading out the photocurrent, under near-UV front steady state background. Data shows that 2⁵ current levels are detected and corresponds to the thirty-two on/off possible states. The proximity of the magnitude of consecutive levels causes occasional errors in the decoded information. To minimize the errors, four parity bit are generated and stored along with the data word. The parity of the word is checked after reading the word to detect and correct the transmitted data. Results show that the background works as a selector in the visible range, shifting the sensor sensitivity and together with the parity check bits allows the identification and decoding of the different input channels. A transmission capability of 60 kbps using the generated codeword was achieved. An optoeletronic model gives insight on the system physics.

An indoor positioning system were trichromatic white LEDs are used both for illumination proposes and as transmitters and an optical processor, based on a-SiC:H technology, as mobile receiver is presented. OOK modulation scheme is used, and it provides a good trade-off between system performance and implementation complexity. The relationship between the transmitted data and the received digital output levels is decoded.

The system topology for positioning is a self-positioning system in which the measuring unit is mobile. This unit receives the signals of several transmitters in known locations, and has the capability to compute its location based on the measured signals. LED bulbs work as transmitters, sending information together with different IDs related to their physical locations. A triangular topology for the unit cell is analysed. A 2D localization design, demonstrated by a prototype implementation is presented. Fine-grained indoor localization is tested. The received signal is used in coded multiplexing techniques for supporting communications and navigation concomitantly on the same channel. The position is estimated through the visible multilateration metodh using several non-collinear transmitters. The location and motion information is found by mapping position and estimates the location areas.

Data analysis showed that by using a pinpin double photodiode based on a a-SiC:H heterostucture as receiver, and RBGLEDs as transmitters it is possible not only to determine the mobile target’s position but also to infer the motion direction over time, along with the received information in each position.

In visible optical communication over the multimode PMMA fibers, the overall cost of optical network can be reduced by deploying economical splitters for distributing the optical data signals from a point to multipoint in transmission network. The low-cost splitters shall have two main characteristics; good uniformity and high power efficiency. The most cost-effective and environmental friendly optical splitter having those characteristics have been developed. The device material is 100% purely based on the multimode step-index PMMA Polymer Optical Fiber (POF). The region which all fibers merged as single fiber is called as fused-taper POF. This ensures that all fibers are melted and fused properly. The results for uniformity and power efficiency of all splitters have been revealed by injecting red LED transmitter with 650 nm wavelength into input port while each end of output fibers measured by optical power meter. Final analysis shows our fused-taper splitter has low excess loss 0.53 dB and each of the output port has low insertion loss, which the average value is below 7 dB. In addition, the splitter has good uniformity that is 32:37:31% in which it is suitably used for demultiplexer fabrication.

In this contribution we study the relation between the second order intensity moments and the Goos-Hänchen shift for partially coherent totally polarized beams. The results are applied to a type of partially coherent beams, the Cosine-Gaussian Schell-model beams with rectangular symmetry.

We propose the development and realization of a plasmonic structure based on the LSP interaction of metal nanoparticles with an embedding matrix of amorphous silicon. This structure need to be usable as the basis for a sensor device applied in biomedical applications, after proper functionalization with selective antibodies. The final sensor structure needs to be low cost, compact and disposable. The study reported in this paper aims to analyze different materials for nanoparticles and embedding medium composition. Metals of interest for nanoparticles composition are Aluminum, Gold and Alumina. As a preliminary approach to this device, we study in this work the optical properties of metal nanoparticles embedded in an amorphous silicon matrix, as a function of size, aspect-ratio and metal type. Following an analysis based on the exact solution of the Mie theory, experimental measurements realized with arrays of metal nanoparticles are compared with the simulations.

In this work we present a study on three types of semiconductor mode-locked lasers as possible sources for a high precision absolute distance metrology measurement concept based on pulse repetition frequency (PRF) sweep. In this work, we evaluated one vertical emission laser and two transversal emission sources. The topology of the gain element is quantum-well, quantum-dot and quantum-dash, respectively. Only the vertical emission laser has optical pump, whilst the others operate with electric pumping. The quantum-dash laser does not have a saturable absorber in its configuration but relies on a dispersion compensating fiber for generating pulses. The bottleneck of vertical emission laser is his high power density pump (4.5W/165μm), increasing the vulnerability of damaging the gain element. The other lasers, i.e., the single (quantum-dash) and double section (quantum-dot) lasers present good results either in terms of applicability to the metrology system or in terms of robustness. Using RF injection on the gain element, both lasers show good PRF stabilization results (better than σ_y(10ms) = 10⁻⁹ ) which is a requirement for the mentioned metrology technique.

According to the earlier author’s papers, the erbium/ytterbium co-doped oxyfluoride glass-ceramics fibers should demonstrate better 1550 nm emission under 488/515/980 nm excitation (the erbium Er³⁺ ion transition ⁴I_13/2→⁴I_15/2) than corresponding glass fibers (the batch composition 48SiO₂11Al₂O₃-7Na₂CO₃-10CaO-10PbO-12PbF₂- 1.5/0.6YbF₃-0.5/0.2ErF₃). Glass fibers provided as a core of standard multimode waveguide (the diameter of 62 μm) have been drawn with the mini-tower to the diameter between 50 μm and 80 μm, then annealed in the two-step regime (580°C/1h – nucleation of nano-crystals; 760oC/15/30 min – nano-crystals growth). This kind of heat treatment ensures the transparent glass-ceramics fibers with the microstructure of homogeneously distributed nano-crystals (lead, erbium and ytterbium enriched cubic fluorite-like crystals and hexagonal PbF₂ crystals) embedded in a glassy host. Their transmission covers the range of 80-90% and seems to be sufficient with respect to their provided limited length (~2m). The luminescence intensity for glass-ceramics fibers at 1530 nm is higher than that of respective glass fibers and the lifetimes of the erbium ion excited state ⁴I_13/2 are of the same order (~5 ms). In that context the glass-ceramics fibers discussed above seem to be promising candidates for cores of fiber lasers at the 1550 nm band.

In this work we present the process of fabrication and optimization of a prototype of a cell electrostimulator device for medical application combining physical vapor deposition and laser ablation. The fabrication of the first prototype begins with a deposition of a thin layer of 200 nm of aluminium on a borosilicate glass substrate using physical vapor deposition (PVD).

In the second stage the geometry design of the electrostimulator is made in a CAD-like software available in a Nd:YVO4 Rofin Power line 20E, operating at the fundamental wavelength of 1064 nm and 20 ns pulse width. Choosing the proper laser parameters the negative of the electrostimulator desing is ablated. After that the glass is assembled between two polycarbonate sheets and a thick sheet of polydimethylsiloxane (PDMS). The PDMS sheet has a round hole in where cells are placed. There is also included a thin soda-lime silicate glass (100 μm) between the electrostimulator and the PMDS to prevent the cells for being in contact with the electric circuit.

In order to control the electrical signal applied to the electrostimulator is used a digital I/O device from National Instruments (USB-6501) which provides 5 V at the output monitored by a software programmed in LabVIEW. Finally, the optical and electrical characterization of the cell electrostimulator device is presented.

The work presented in this paper supports the viability of a navigation system based on Visible Light Communication (VLC) for indoors applications. The system design uses RGB LEDs and an a:SiC:H photodetector.

An optoelectronic characterization of the devices used in the integrated system is presented to support the main results, namely the decoding strategy. The photodetector is a pin-pin heterostructure that works as an optical filter, presenting a selective spectral sensitivity dependent on the external optical bias. The red and blue light emitted from the white RGB LEDs were modulated at different frequencies. With this configuration each cardinal direction becomes assigned to a specific set of optical excitation (wavelength and frequency). The decoding of the output photocurrent allows the identification of the input optical signals and the determination of the correspondent spatial direction. The localization algorithm makes use of the Fourier transform to identify the frequencies present in the photocurrent signal and the wavelength filtering properties of the sensor under front and back optical bias to detect the existing red and blue signals. The viability of the system is demonstrated through the implementation of an automatic algorithm to infer the photodetector cardinal direction. Additional research on the light intensity is presented to investigate the accuracy of the spatial position along a cardinal direction.

Sun´s ultraviolet radiation is classified into UV-A, UV-B, and UV-C bands. Thereby UV-A passes through Earth´s atmosphere, while UV-B is partially absorbed by ozone. The limitations of the commonly accepted statement, that UV-C is always completely absorbed by Earth´s atmosphere, are discussed critically. Below 200 nm the solar spectrum is strongly absorbed by molecular oxygen. The stratospheric ozone layer has strong absorption between 200 nm and 300 nm. However, the “ozone hole” increases UV-B radiation just below 300 nm and may also open a transmitting atmospheric window for harmful UV-C at the overlap region between oxygen absorption and ozone absorption.

Photo-thermo-refractive glass is a promising material because it combines the properties of several monofunctional materials in it. These glasses can be doped with rare earth ions and can then be used for many practical applications. But the major problem is the low absorption coefficient. So, a lot of research has been done to grow silver nanoclusters and nanoparticles for improving the spectroscopic properties of rare-earth ions. In this study we present a way to transfer energy from silver clusters to Eu³⁺ ions in the PTR glass. These results can be used for developing warm white LEDs and down converters for solar cells.

We have investigated the change in optical properties and biocompatibility of up-converting NaYF4 nanoparticles (NPs) upon encapsulation inside the polyester nanocarriers (NCs) stabilized by Crempophor RH40 (CRH40), poly(D,L-lactide) (PLA), Pluronic P123 (P123). NaYF₄:Er³⁺,Yb³⁺ NPs showed intense green and red emission, and upon encapsulation the increase of red band in respect to green one was observed, with no luminescence lifetime shortening. Obtained NCs showed prolonged colloidal stability and protective effect of the polymer shell simultaneously preserving the high emission efficiency of nanoparticles embedded within the silicon oil (SO) core. Based on emission spectra, kinetic measurements and cytotoxicity studies upon human malignant melanoma Me45 cell line we have shown the advantages of using polyester NCs as containers for the up-converting NPs. Due to the possibility of co-encapsulation of photosensitizers the obtained nanocarriers showed potential for application in theranostics.

Current clinical optical imaging systems do not provide sufficient structural information of trabecular meshwork (TM) in the iridocorneal angle (ICA) of the eye due to their low resolution. Increase in the intraocular pressure (IOP) can occur due to the abnormalities in TM, which could subsequently lead to glaucoma. Here, we present an indirect gonioscopy based imaging probe with significantly improved visualization of structures in the ICA including TM region, compared to the currently available tools. Imaging quality of the developed system was tested in porcine samples. Improved direct high quality visualization of the TM region through this system can be used for Laser trabeculoplasty, which is a primary treatment of glaucoma. This system is expected to be used complementary to angle photography and gonioscopy.

In this communication we analyze the light field distribution of a highly focused radially polarized beam when passes through a linear polarizer. The polarizer is modeled as a plane-parallel uniaxial absorbing medium with the optical axis parallel to the plate surfaces of the polarizer. Analytical results and numerical calculations are provided.

A preclinical device that mimics half blood vessel by using laser technologies has been developed. By employing a Nd:YVO₄ laser a channel has been manufactured over soda-lime glass. Using a CO₂ laser combined with a roller furnace, a thermal treatment has been applied to the channel to enhance its quality. The glass structure was employed as master to replicate the channel in PDMS by soft-lithography. To avoid the deterioration of the PDMS, channels were coated with three different sol-gel coatings compositions. Endothelial cells were cultured over the channels to determine the most suitable surface for cell growing.

Purpose: Different lower tear meniscus parameters can be clinical assessed on dry eye diagnosis. The aim of this study was to propose and analyse the variability of a semi-automatic method for measuring lower tear meniscus central area (TMCA) by using open source software. Material and methods: On a group of 105 subjects, one video of the lower tear meniscus after fluorescein instillation was generated by a digital camera attached to a slit-lamp. A short light beam (3x5 mm) with moderate illumination in the central portion of the meniscus (6 o’clock) was used. Images were extracted from each video by a masked observer. By using an open source software based on Java (NIH ImageJ), a further observer measured in a masked and randomized order the TMCA in the short light beam illuminated area by two methods: (1) manual method, where TMCA images was “manually” measured; (2) semi-automatic method, where TMCA images were transformed in an 8-bit-binary image, then holes inside this shape were filled and on the isolated shape, the area size was obtained. Finally, both measurements, manual and semi-automatic, were compared. Results: Paired t-test showed no statistical difference between both techniques results (p = 0.102). Pearson correlation between techniques show a significant positive near to perfect correlation (r = 0.99; p < 0.001). Conclusions: This study showed a useful tool to objectively measure the frontal central area of the meniscus in photography by free open source software.

We present two ferrofluids in which high variations of optical transmission can be induced by application of moderate magnetic fields (obviously a desirable feature of functional substances aimed at photonic applications). The samples tested are representative of two different behaviors observed in ferrofluids. Exposed to a magnetic field, the size of the aggregates are much smaller in sample 1 than in sample 2, and once the magnetic field is turned off, aggregates disappear in sample 1 while they stay in sample 2. The transmission of samples 2 mm thick, as a function of magnetic field (up to 72 G), are compared. For ferrofluid 1, its transmission increases up to 40% or decreases up to 75% by applying a magnetic field perpendicular or parallel to the incident light respectively. For ferrofluid 2, the presence of a magnetic field parallel to the incident light can multiply its transmission by a factor up to 160. In both samples, the transmission dependence on the applied magnetic field shows an acceptable linearity, which is a very interesting feature face to eventual sensing applications. Besides, it is shown how aggregates favor a drastic temporal response after DC magnetic field switch on and off.

This paper intends to propose a monolithic photonic integrated InP transceiver for Next Generation of Ethernet Passive Optical Network (NG-EPON). The presented architecture was designed as an Optical Network Unit (ONU). The concept behind the suggested transceiver architecture is here presented together with the steps necessary to deploy the proposed solution.

In this report, we inform in detail on fabrication of a special (3 rings of air-holes) index-giuding air-silica microstructured optical fiber (IG MOF) with different air-hole diameters in the cladding (irregular cladding) and its application for a broadband supercontinuum (SC) generation by femtosecond laser pulses. For comparison, supercontinuum generation in a special nonlinear air-silica IG MOF with regular cladding is also investigated. Dispersion properties of the investigated fibers were numerically predicted and experimentally verified. Broadband SC generation from visual wavelengths up to 1600 nm in such fibers, both with the length of 1 m, was observed.

Active integrated multicore waveguide structures (AIMWS) with high refractive index contrast values and controlled local composition can be fabricated inside a bulk doped glass as a result of recent developments in high repetition femtosecond laser writing. The modeling of these structures presents some distinct characteristics when compared to that of corresponding multicore fiber structures. In this paper we present a study of the influence of two of these features in the signal amplification: the glass homogeneous doping and the existence of a zone of depressed refractive index. In order to do that, we use a home-made computer code that solves the optical power propagation equations of the structure supermodes coupled to the rate equations of the active ions.

Purpose: To validate the performance of a new objective application designated iDEAS (Dry Eye Assessment System) to categorize different zones of lipid layer patterns (LLPs) in one image. Material and methods: Using the Tearscopeplus and a digital camera attached to a slit-lamp, 50 images were captured and analyzed by 4 experienced optometrists. In each image the observers outlined tear film zones that they clearly identified as a specific LLP. Further, the categorization made by the 4 optometrists (called observer 1, 2, 3 and 4) was compared with the automatic system included in iDEAS (5th observer). Results: In general, observer 3 classified worse than all observers (observers 1, 2, 4 and automatic application, Wilcoxon test, <0.05). The automatic system behaved similar to the remaining three observers (observer 1, 2 and 4) showing differences only for Open meshwork LLP when comparing with observer 4 (Wilcoxon test, p=0.02). For the remaining two observers (observer 1 and 2) there was not found statistical differences (Wilcoxon test, >0.05). Furthermore, we obtained a set of photographs per LLP category for which all optometrists showed agreement by using the new tool. After examining them, we detected the more characteristic features for each LLP to enhance the description of the patterns implemented by Guillon. Conclusions: The automatic application included in the iDEAS framework is able to provide zones similar to the annotations made by experienced optometrists. Thus, the manual process done by experts can be automated with the benefits of being unaffected by subjective factors.

We report on some recent advances in industrial color-difference evaluation focused in three main fields: Development of reliable experimental visual datasets; proposal of new color spaces and color-difference formulas; tools to evaluate the merits of color-difference formulas. The use of fuzzy techniques to assign consistency degrees to color pairs in combined visual datasets is described. The CIE/ISO joint proposal of the CIEDE2000 color-difference formula as a standard will facilitate the communication among companies and users. The CIE recommendation of the STRESS index to assess observers’ variability and relative merits of different color-difference formulas is reported. Power functions are an efficient method to improve the performance of modern color-difference formulas. We need of advanced color-difference formulas accounting for new materials with different kind of textures and gonioapparent effects.

Interesting plasmonic effects can arise from the combination of small polarisable particles with graphene, related to surface plasmon-polaritons (SPPs) supported by the latter in the terahertz (THz) spectral range. The electromagnetic coupling between graphene SPPs and dipole moments of nanoparticles (NPs) deposited on top of it gives rise to optical properties that aren’t present in the individual components of this system. The NPs’ polarisability is renormalized due to the electromagnetic back action of the SPPs which are excited in graphene when an external propagating electromagnetic wave impinges on the particle. Moreover, beyond the usual dipole-dipole interaction, an indirect particle-particle coupling arises via polarisation charges induced on the graphene-covered interface by each particle – this indirect coupling oscillates with the interparticle distance. We derived coupled-dipole equations taking into account all these effects, allowing us to calculate an effective optical conductivity of the particles’ monolayer. One of the G+NPs system’s unique properties is a collective polariton mode, causing a considerable enhancement of the THz radiation absorption in graphene, while the reflection drops to nearly zero for a broad range of angles of incidence. The frequency of this resonant mode can be adjusted by changing the Fermi energy in graphene via electrostatic gating and therefore it can be used for electrically controlled reflection and transmission of THz radiation

The possibility of using lasers diodes and a fiber optic trifurcated for the evaluation of the power optic absorbed on coals samples is studied. The method is based on scanning of samples using lasers diodes with the wavelengths 632,8nm, 532nm, 405nm, and calibration plots of the reflected luminosity of the selection as function of the absorbance of coals. In this paper we showed the calibration plots and the colorimetric parameters of coals calculated from the absorption or diffuse-reflectance. The advantages of the method are its high performance for estimating the colorimetric parameters of coals samples, quality control of industrial processes and classification of coals.

A hydrodynamic model was developed that takes into account the kinetics of heterogeneous phase transitions (melting and evaporation) under the action of pulsed laser radiation on metal targets. With the use of continual and molecular dynamic modeling, the initial stage of the explosive boiling of an Al target under the influence of ns laser radiation was studied. The simulation confirmed the presence of a temperature maximum below the surface of superheated metastable liquid underlying the homogeneous evaporation (phase explosion) of metals.

The article discusses the use of mathematical modeling to obtain properties of silicon. The nonequilibrium heating of semiconductor proceeds with a large separation of temperatures of the current carriers from the lattice, therefore, in the problems of laser action a silicon target can be regarded as an object consisting of two interacting subsystems, electron and phonon subsystems. At the same time, for each of subsystems it is necessary to determine thermophysical, optical and thermodynamic characteristics that vary over a wide temperature range. To determine the properties of the electronic subsystem a continual approach was used, and for the phonon subsystem a molecular-dynamic approach was used. Such properties of the electron Fermi gas as electron concentration N_e(T), holes concentration N_h(T), Fermi energy E_F(T), band gap E_g(T,N), carrier mobility μ(T,N), electrical conductivity σ(T,N) are determined within the framework of quantum statistics in an arbitrary degeneracy range when the temperature varies from 300K to 2000K. The most important characteristics of the phonon subsystem such as the pressure dependences of the melting temperature of silicon T_m(P) and the heat of melting L_m(P), and the temperature dependence of the heat of evaporation L_v(T) were determined. The results are compared with the experimental data.

In the past several decades, the Finite-Difference Time-Domain (FDTD) method has become one of the most powerful numerical techniques in solving the Maxwell’s curl equations and has been widely applied to solve complex optical and photonic problems. This method divides space and time into a regular grid and simulates the time evolution of Maxwell’s equations. This paper reports some results, obtained by a set of FDTD simulations, about the characteristics of amorphous silicon waveguides embedded in a SiO2 cladding. Light absorption dependence on the material properties and waveguide curvature radius are analysed for wavelengths in the infrared spectrum. Wavelength transmission efficiency is determined analysing the decay of the light power along the waveguides and the obtained results show that total losses should remain within acceptable limits when considering curvature radius as small as 3 μm at its most.

This paper shows the progress made in the wavemeter developed to give traceability to the wavelength of lasers and ECDLs (External Cavity Laser Diode). The improvements are: duplication of the optical path of the laser beams due to a double pass through the interferometer arms [1], the electronic fringe counter [2], the measurement of the refractive index of air and the uncertainty calculations of the wavelength for the case of lasers with frequencies that differs more than 10 THz from laser reference. The new measurements improve the previous results [3].

The problem of electromagnetic wave propagation in time varying media is very old, but in recent years it has been revisited at a more fundamental level leading to the introduction of several new concepts, such as Time Refraction. These concepts explore the symmetries between space and time and can be transposed to different fields by establishing powerful analogies between effects in Electrodynamics, Optics and problems in Quantum Cosmology and in what is sometimes called Analogue Gravity. We examine the alteration of the ordinary (spatial) Fresnel laws of refraction at the interface between two media when the optical properties of one of the media varies in time.

Single cell analysis can provide important information regarding cell composition, and can be used for biomedical applications. In this work, a SERS active substrate formed by 3 layers of gold nanospheres and a final layer of gold nanocubes was used for the label-free SERS analysis of HeLa cells. Nanocubes were selected due to the high electromagnetic enhancement expected in nanoparticles with sharp corners. Significant improvement in the reproducibility and quality of SERS spectra was found when compared to the spectra obtained using a nanosphere-only substrate and normal Raman spectroscopy.

Optical properties of experimental graphene dental nanocomposites were studied. Spectral reflectance was measured and S and K coefficients as well as transmittance of samples were calculated using Kubelka-Munk’s equations. The spectral behavior of S, K and T experimental graphene exhibited different trends compared with the commercial nanocomposites and they were statistically different. Experimental nanocomposites show higher scattering and lower transmittance when compared with commercial nanocomposite, probably, due to the shape, type and size of the filler. K for short wavelength of the pre-polymerized experimental nancomposites was very low. According to our results, hidroxypatite with graphene oxide used in dental nanocomposites needs to be improved to reproduce esthetic properties of natural dental tissues and to have potentially clinical applications.

Localized plasmons in metallic nanostructures present strong analogies with Quantum Mechanical problems of particles trapped in potential wells. In this paper we take this analogy further using the Madelung Formalism of Quantum Mechanics to express the fluid equations describing the charge density of the conduction electrons and corresponding interaction with light in terms of an effective generalized Non-linear Schr¨odinger equations. Within this context, it is possible to develop the analogy of a plasmonic atom and molecule that exhibits Rabi oscillations, Stark effect, among other Quantum Mechanical effects.

We present a numerical implementation of a solver for the Maxwell-Bloch equations to calculate the propagation of a light pulse in a nonlinear medium composed of an atomic gas in one, two and three dimensional systems. This implementation solves the wave equation of light using a finite difference method in the time domain scheme, while the Bloch equations for the atomic population in each point of the simulation domain are integrated using splitting methods. We present numerical simulations of atomic-gas systems and performance benchmarks.

In this paper we analyse the effects of the Doppler shift on the optical response of a nanoplasmonic system. Through the development of a simplified model based on the Hydrodynamic Drude model we analyse the response of a quantum dot embed in a moving fluid, predicting the Doppler broadening and the shift of the spectral line.

In this paper we report on the development of a numerical solver for Vlasov equations based on heterogeneous supercomputing using GPGPUs. The solver adapts techniques from many-body simulation, namely the particlein-cell approach, to describe the interaction between the electromagnetic field and atomic gas whose internal state can be described by the multilevel Bloch equations. We also present the benchmark and performance analysis of the code. We investigate the interaction between two coherent light beams, as a case of study to demonstrate the validation of the code.

In this work we address the development of a fast solver of the ray-tracing equations based on heterogeneous supercomputing using PyOpenCL. We apply this solver to the study of gravitational lensing and light propagation in optical systems.

Surface-Enhanced Raman Spectroscopy (SERS) is a powerful surface-sensitive technique to study the vibrational properties of analytes at very low concentrations. In this study, ferulic acid, p-coumaric acid, caffeic acid and sinapic acid were analyzed by SERS using Ag colloids. Analytes were detected up to 2.5x10^-9M. For caffeic acid and coumaric acid, this detection limit has been reached for the first time, as well as the SERS analysis of sinapic acid using silver colloids.

The realization of tabletop optical analogue experiments of superfluidity relies on the engineering of suitable optical media, with tailored optical properties. This work shows how quantum atomic optical systems can be used to develop highly tunable optical media, with localized control of both linear and nonlinear susceptibility. Introducing the hydrodynamic description of light, the superfluidity of light in these atomic media is investigated through GPU-enhanced numerical simulations, with the numeric observation of the superfluidic signature of suppressed scattering through a defect.

Here we explore the possibility of controlling the inhomogeneities in quasi-1D Bose-Einstein condensates using a spatial variation of the transverse confinement potential and explore different optical strategies to realize these pinched traps. Furthermore, we also present some early stage results on the dynamics of matter-wave solitons in such systems using computational simulations of the full 3D Gross-Pitaevskii equation.

In this work we develop a theoretical model to describe the propagation of an optical pulse in a 4-level atomic system. We investigate the existence of dissipative soliton solutions and analyze the stability of these solitary waves, comparing the analytical results with computational simulations based on the effective (1+1)-dimensional model derived from the Maxwell-Bloch equation under the slowly-varying envelope approximation.

Wavefront coding (WFC) enables the depth of field of incoherent optical systems to be extended. This method involves a cubic-phase plate in the system yielding a blurred image nearly invariant to defocus. In visual optics there is a big interest in improving solutions for two different problems: Presbyopia correction and high resolution retinal images with low cost devices. In this work we will show how the use of cubic phases in contact lenses can be an alternative to multifocal lenses and how WFC technique can be applied to record high resolution retinal images reducing the complexity of the actual systems

Under specific conditions, there is a formal analogy between the fundamental equations of electromagnetism and relativistic gravitation, described by the Einstein field equations of general relativity. In this paper, we report on how we have used this analogy to implement a solver of the Einstein equations adapting algorithms initially developed for electromagnetism, combined with methods of heterogeneous supercomputing, in GPU that can achieve fast computing and exhibit good performance. We also present the results of the simulations used to validate our solver.

The use of nanoparticles is spreading in many fields and a frequent way of preparing them is in the form of colloids, whose characterization becomes increasingly important. The spectral reflectance and transmittance curves of such colloids exhibit a strong dependence with the main parameters of the system. By means of a two-flux model we have performed a colorimetric study of gold colloids varying several parameters of the system, including the radius of the particles, the particle number density, the thickness of the system and the refractive index of the surrounding medium. In all cases, trajectories in the L*a*b* color space have been obtained, as well as the evolution of the luminosity, chroma and hue, either for reflectance or transmittance. The observed colors agree well with typical colors found in the literature for colloidal gold, and could allow for a fast assessment of the parameters involved, e.g., the radius of the nanoparticle during the fabrication process.

A new method for calculating the effective dielectric function of a metal-oxide core-shell nanoparticle is presented and compared with existing theories. This new approach can be helpful for predicting the reflectance, transmittance and absorbance spectra of core-shell colloids and nanocomposites which are widely used in photocatalysis or solar energy harvesting.

A technique of computational image encryption and optical decryption based on computer generated holography and time-averaged moir´e is investigated in this paper. Dynamic visual cryptography (a visual cryptography scheme based on time-averaging geometric moir´e), Gerchberg–Saxton algorithm and 3D microstructure manufacturing techniques are used to construct the optical scheme. The secret is embedded into a cover image by using a stochastic moir´e grating and can be visually decoded by a naked eye. The secret is revealed if the amplitude of harmonic oscillations in the Fourier plane corresponds to an accurately preselected value. The process of the production of 3D microstructure is described in details. Computer generated holography is used in the design step and electron beam lithography is exploited for physical 3D patterning. The phase data of a complex 3D microstructure is obtained by Gerchberg-Saxton algorithm and is used to produce a computer generated hologram. Physical implementation of microstructure is performed by using a single layer polymethyl methacrylate as a basis for 3D microstructure. Numerical simulations demonstrate efficient applicability of this technique.

The aim of this paper is to examine the effect of pig bone immersion in different levels of cooling water during laser ablation with a Er:YAG laser. The laser worked at 2940 nm wavelength and 10 Hz repetition rate in microseconds pulse duration regime. The bone was immersed in different levels of cooling water in a sample container for preventing carbonization. The bone samples were ablated with fixed deposited energy to investigate at which water level Er:YAG lasers start ablating bone through a layer of water. Results showed that the maximum level of water that laser can pass through to start the ablation nonlinearly depends on pulse energy.

Imaging polarimetry is a focus of increasing interest in diagnostic medicine because of its non-invasive nature and its potential for recognizing abnormal tissues. However, handling polarimetric images is not an easy task, and different intermediate steps have been proposed to introduce physical parameters that may be helpful to interpret results. In this work, transmission Mueller matrices (MM) corresponding to cancer cell samples have been experimentally obtained, and three different transformations have been applied: MM-Polar Decomposition, MM-Transformation and MM-Differential Decomposition. Special attention has been paid to diattenuation as a sensitive parameter to identify apoptosis processes induced by cisplatin and etoposide.

This work presents seasoning behavior from a set of 1000 W FEL-type lamp concerning its qualification to be used as a secondary spectral irradiance standard. The lamps from the set were made from two different manufactures and were seasoned for a period of 40 hours. During the seasoning, lamp relative drift of irradiance, illuminance, current and voltage were measured at each 3 minutes and lamp spectral irradiance relative drift was measured 4 times. It was observed significant temperature dependence in the irradiance measurement related to meter readout circuit. Despite the temperature effect, it was obtained the average irradiance stability up to 0.03%/h and illuminance stability up to 0.02%/h.

In this paper we discuss the development of a fast ray-tracing solver for complex anisotropic uniaxial optical media based on heterogeneous supercomputing in GPGPU using PyOpenCl. This solver simulates both the propagation of ordinary and extraordinary rays, while taking into account the polarization rotation introduced by position dependent modulations of the optical axis of the medium. We demonstrate the application of this solver by simulating the generation of polarization caustics in random uniaxial optical media.

This paper presents an overview of the Haar Wavelet Transform applied with a Multimode Interferometer. The Haar Wavelet Transform is one of the most used compressing method due to its fast computation and uncomplicated design. It only requires an averaging and differencing method, making it possible to easily decompose and compress an image. Based on Soldano1 self-imaging numerical approach and Besse design,² an 2 x 2 Multimode Interferometer with modified access waveguides is presented as solution. Using Beam Propagation Method simulations, the solution was tested, analysed and applied on an Haar Network.

In this work a new type of partially polarized and partially coherent sources is proposed. The coherence characteristics of these sources are dependent on the difference of the radial distances from the source center of the two points to be compared. The coherence is perfect for points located on the same circle centered on the source center and decreases for points that belongs to different concentric circles. The maximum attainable coherence is related to the degree of polarization of the source. Coherence and polarization characteristics of this kind of fields at the source plane and upon free space propagation are analyzed in detail for a simple case. For the particular presented example, a partially polarized and partially coherent field is obtained, whose polarization properties are invariant in propagation.

In this paper, tunability of three near-infrared semiconductor lasers which typically lase at 808 nm, 892 nm and 980 nm is studied. Both Littrow (wavelength dependent beam direction setup) and Littman (wavelength independent beam direction setup) configurations have been used. The wavelength and the power of the output beam of the laser have been measured. In all three cases, Littrow configuration shows a little better tuning range. In both Littrow and Littman configurations the wavelengths near the main wavelength of the laser had more power. The highest achieved power of these lasers in the Littrow setup was more than that of the Littman setup.

The objective of this work is to quantify the suppressive imbalance, based on the manipulation of ocular luminance, between a group of subjects with normal binocular vision and a group of subjects with amblyopia.

The result reveals that there are statistically significant differences in interocular dominance between two groups, evidencing a greater suppressive imbalance in amblyopic subjects.

The technique used, proved to be a simple, easy to apply and economic method, for quantified ocular dominance. It is presented as a technique with the potential to accompany subjects with a marked dominance in one of the eyes that makes fusion difficult.

In this paper, we propose a new multiparametric optical fiber transducer applied to an electric generator of 370 MVA. The optical transducer has three multiplexed FBGs in the same optical fiber as the sensing element. The FBG sensors can simultaneously measure both the temperature and vibration independently of the other multiplexed FBGs. The installation in the power plant was performed using six transducers and it was obtained 23 hours of simultaneous vibration and temperature measurement. All the FBGs used to monitor generator vibration were able to monitor the frequency of mechanical and electromagnetic vibrations, which were measured at 2 Hz and 120 Hz, respectively. During the measurement, the machine was turned off due to a failure and all the FBGs sensed temperature changes, as well as frequency vibration changes. The largest temperature difference measured between the FBGs during the test is approximately 2°C.

A visible fiber Bragg grating (Vis-FBG) with wavelength peak centered at 673.07 nm was inscribed in a multimode fiber designed for infrared (IR) operation using a femtosecond (fs) laser emitting at 248 nm. The fiber cladding is removed by chemical etching in hydrofluoric acid solution (40%). The sensor refractive index response is determined by dipping the sensor into diluted glycerin solution at different concentrations with refractive index range from 1.3328 to 1.4607. The Vis-FBG performance is compared with an IR etched FBG (EFBG) with similar diameter. The sensitivity found for the Vis-FBG sensor is 15.71nm/RIU with a 6.34 x 10^-3 RIU resolution for a refractive index of 1.4607.

The aim of the present study is to investigate the effect of laser pulse duration on ablation efficiency of hard bones. The bones were ablated using a microsecond pulsed Er-YAG laser. The laser wavelength was 2.94 μm and the repetition rate was 10Hz. Three samples of porcine femur were used and several areas were ablated with a fixed pulse energy of 280mJ and different pulse durations. The ablation procedure was applied during five seconds for all the experiments, therefore, the same amount of energy (14 J) was deposited in each trial. The ablation efficiency was determined by measuring the ablated volume per second for each experiment.

Given the increasing necessity of simple, economical and reliable methods and instruments for performing quality tests of optical surfaces such as mirrors and lenses, in the recent years we resumed the study of the long forgotten Foucault knife-edge test from the point of view of the physical optics, ultimately achieving a closed mathematical expression that directly relates the knife-edge position along the displacement paraxial axis with the observable irradiance pattern, which later allowed us to propose a quantitative methodology for estimating the wavefront error of an aspherical mirror with precision akin to interferometry.

In this work, we present a further improved digital image processing algorithm in which the sigmoidal cost-function for calculating the transient slope-point of each associated intensity-illumination profile is replaced for a simplified version of it, thus making the whole process of estimating the wavefront gradient remarkably more stable and efficient, at the same time, the Fourier based algorithm employed for gradient integration has been replaced as well for a regularized quadratic cost-function that allows a considerably easier introduction of the region of interest (ROI) of the function, which solved by means of a linear gradient conjugate method largely increases the overall accuracy and efficiency of the algorithm.

This revised approach of our methodology can be easily implemented and handled by most single-board microcontrollers in the market, hence enabling the implementation of a full-integrated automatized test apparatus, opening a realistic path for even the proposal of a stand-alone optical mirror analyzer prototype.

Light acquires or loses coherence and coherence is one of the few optical observables. Spectra can be derived from coherence functions and understanding any interferometric experiment is also relying upon coherence functions. Beyond the two limiting cases (full coherence or incoherence) the coherence of light is always partial and it changes with propagation. We have implemented a code to compute the propagation of partially coherent light from the source plane to the observation plane using parallel computing devices (PCDs). In this paper, we restrict the propagation in free space only. To this end, we used the Open Computing Language (OpenCL) and the open-source toolkit PyOpenCL, which gives access to OpenCL parallel computation through Python. To test our code, we chose two coherence source models: an incoherent source and a Gaussian Schell-model source. In the former case, we divided into two different source shapes: circular and rectangular. The results were compared to the theoretical values. Our implemented code allows one to choose between the PyOpenCL implementation and a standard one, i.e using the CPU only. To test the computation time for each implementation (PyOpenCL and standard), we used several computer systems with different CPUs and GPUs. We used powers of two for the dimensions of the cross-spectral density matrix (e.g. 32⁴, 64⁴) and a significant speed increase is observed in the PyOpenCL implementation when compared to the standard one. This can be an important tool for studying new source models.

The objective of this study was to characterize the photo activation reaction of experimental graphene dental nanocomposites and to compare this reaction between commercial nanocomposite by dynamic laser speckle patterns. One commercial nanocomposite and two experimental graphene nanocomposites were used. LED curing unit was used to produce the photo activation reaction and the speckle patterns were generated by the incident light from the laser diode. These patterns were captured with the CMOS camera; later the speckle correlation was calculated. The photo activation process originates different speckle patterns between the commercial and the experimental graphene nanocomposites; having this less speckle activity.

In this work, we present the application of a nonlinear control system, based on variable structure control and sliding modes, to a fiber optic Mach-Zehnder interferometer. We showed that this control system is able to keep the interferometer in quadrature, suppress the signal fading, lead to high accuracy control, featuring ease of implementation and high robustness. Thus, the controlled interferometer was employed for the measurement of frequency response and mechanical resonances of a cylindrical piezoelectric actuator. The advantages of an all-fiber interferometric sensor combined with the proposed nonlinear control system features compactness, light weight, alignment free, electromagnetic immunity, high sensitivity, geometric versatility, robustness, real-time high precision measurement, and possibility of operation in harsh environments.

An experimental study aiming to develop a model based on CIELAB color space for prediction of color change after a tooth bleaching procedure is presented. Multivariate linear regression models were obtained to predict the L*, a*, b* and W* post-bleaching values using the pre-bleaching L*, a*and b*values. Moreover, univariate linear regression models were obtained to predict the variation in chroma (C*), hue angle (h°) and W*. The results demonstrated that is possible to estimate color change when using a carbamide peroxide tooth-bleaching system. The models obtained can be applied in clinic to predict the colour change after bleaching.

This paper describes a flexible model that can be used to simulate laser-based photoactivation of drug delivery systems. It considers Gaussian beams for the excitation while the heat diffusion equation is solved by use of the finite element method. As an example, a typical liposome geometry in the focal volume of a laser beam is simulated and the results are compared with experimental data obtained in the literature, showing a good agreement. The model has potential in the design of drug delivery systems as it can be a starting point for the development of new kinds of micro- and nano-scale drug delivery systems.

The response of short-length CO2 -induced Long Period Fiber Gratings (LPFGs) sensors to torsion is reported. While engraving, the fiber is submitted to high tension allowing to obtain gratings with shorter lengths, one order of magnitude lower than the usual. Also, the fiber was only irradiated in one side, creating an asymmetrical profile leading to highly birefringent gratings. Good sensitivity to axial twists is demonstrated, with values up to 0.12 nm/(rad/m) for the resonant wavelength shift, and better than 0.03 dBm/(rad/m) for the variation in the intensity (attenuation). Discrimination between rotation direction, clockwise and counterclockwise, can be obtained.

Ultrashort pulses with time durations on the femtosecond scale can be suitably processed by microoptical devices. The temporal impulse response of an element is determined by its spatial structure, its action in the temporal domain can be conveniently described by its impulse response. All categories of elements can be used: refractive, diffractive and reflective. Here, the basic concepts are discussed and several examples for shaping and filtering short pulses are presented.

A Fabry-Perot interferometer based on an array of soda-lime glass microspheres is proposed for temperature sensing. The microspheres are introduced in a hollow-core silica tube using a tapered fiber tip. After the insertion of each microsphere the sensor is subjected to temperature measurements. The sensor exhibits non-linear behavior and a dependence on the number of microspheres is observed. A maximum sensitivity of 11.13 pm/°C is achieved, when there is only one microsphere inside the capillary structure.

In Digital Holography (DH), the size of the bidimensional image sensor to record the digital hologram, plays a key role on the performance of this imaging technique; the larger the size of the camera sensor, the better the quality of the final reconstructed image. Scientific cameras with large formats are offered in the market, but their cost and availability limit their use as a first option when implementing DH. Nowadays, DSLR cameras provide an easy-access alternative that is worthwhile to be explored. The DSLR cameras are a wide, commercial, and available option that in comparison with traditional scientific cameras, offer a much lower cost per effective pixel over a large sensing area. However, in the DSLR cameras, with their RGB pixel distribution, the sampling of information is different to the sampling in monochrome cameras usually employed in DH. This fact has implications in their performance. In this work, we discuss why DSLR cameras are not extensively used for DH, taking into account the problem reported by different authors of object replication. Simulations of DH using monochromatic and DSLR cameras are presented and a theoretical deduction for the replication problem using the Fourier theory is also shown. Experimental results of DH implementation using a DSLR camera show the replication problem.

The generation of non-uniformly totally polarized beams and the study of their applications is a subject of increasing interest in the last years. A particular class of beams of this kind are the so-called full Poincaré beams, which have the property of presenting all possible polarization states across their transverse section. Here we present a simple and easy way to obtain a beam endowed with such property. The method is based on the use of an initially linearly polarized beam that propagates along the optic axis of a uniaxial crystal.

A microfiber knot resonator integrated in an abrupt taper-based Mach-Zehnder interferometer was used for simultaneous measurement of temperature and refractive index. This compact structure was fabricated using only CO₂ laser processing. The transmission spectrum is the combination of the microfiber knot resonator and the Mach-Zehnder interferometer responses. The two different components of the transmission spectrum (the microfiber knot resonator and the Mach-Zehnder interferometer components) present different sensitivities when subjected to physical or chemical parameters. A characterization in temperature, refractive index, and sodium chloride (NaCl) concentration was performed. A simple matrix method was used for simultaneous measurement of temperature and refractive index.

Thermal sensitivity increase of regenerated fiber Bragg gratings (RFBG) in the visible range is reported. The FBGs are produced by direct illumination under the phase mask using UV light from two different laser sources at 248 nm. After regeneration the thermal sensitivity is obtained at 500°C to avoid spectra vanishing for temperatures near that of regeneration. At 500°C, the determined thermal sensitivities are 5.74pmK^-1 before and 7.65pmK^-1 after regeneration (single mode fiber in the visible, femtosecond laser), and a similar pattern is presented for all regenerated FBGs.

Fusion splicing technique was explored for the fabrication of two sensing structures based on hollow microsphere Fabry- Perot cavity. The first sensor proposed was fabricated with a hollow microsphere tip, working as a probe sensor. This structure was studied for lateral load pressure, yielding a 1.56 ± 0.01 nm/N sensitivity. The second sensing structure relied on an in-line hollow microsphere, which allowed the detection of lateral load, with a sensitivity of 2.62 ± 0.02 nm/N. Furthermore, the proposed structure enabled strain sensing, with a sensitivity of 4.66 ± 0.03 pm/με. The two sensing structures were subjected to temperature, presenting low thermal cross-sensitivity.

Fibre Bragg sensors are a key device in biomedical research for simultaneous measurement of deformations and temperature. The present study shows results from the characterization of dental resin materials with different composition and applications. The results show that all investigated polymer materials demonstrate a temperature rise within the first few seconds after starting activation procedure. The mode of activation and the material composition influence the polymerization shrinkage values.

The approach dentistry to dental care is gradually shifting to a model focused on early detection and oral-disease prevention; one of the most important methods of prevention of tooth decay is opportune diagnosis of decay and reconstruction. The present study aimed to introduce a procedure for early diagnosis of tooth decay and to compare result of experiment of this method with other common treatments. In this setup, a laser emitting infrared light is injected in core of one bifurcated fiber-optic and conduced to tooth surface and with the same bifurcated fiber the radiation reflected for the same tooth is collected and them conduced to surface of sensor that measures thermal and light frequencies to detect early signs of decay below a tooth surface, where demineralization is difficult to spot with x-ray technology. This device will can be used to diagnose tooth decay without any chemicals and rays such as high power lasers or X-rays.

We present the results of the noise and occlusion tests in the Gyrator domain (GD) for a joint transform correlator-based encryption system. This encryption system was recently proposed and it was implemented by using a fully phase nonzero-order joint transform correlator (JTC) and the Gyrator transform (GT). The decryption system was based on two successive GTs. In this paper, we make several numerical simulations in order to test the performance and robustness of the JTC-based encryption-decryption system in the GD when the encrypted image is corrupted by noise or occlusion. The encrypted image is affected by additive and multiplicative noise. We also test the effect of data loss due to partial occlusion of the encrypted information. Finally, we evaluate the performance and robustness of the encryption-decryption system in the GD by using the metric of the root mean square error (RMSE) between the original image and the decrypted image when the encrypted image is degraded by noise or modified by occlusion.

The USC-OSA Student Chapter and USC-EPS Young Minds Section is a group financed by The Optical Society (OSA) and the European Physical Society (EPS). It is formed by PhD and degree students from the Universidade de Santiago de Compostela (USC) and one supervisor of the Faculty of Physics. Its main goal is to promote and diffuse Optics in the society. For this purpose, the group carries out several activities in the academic and non-academic community. The group is also committed to the professional development of our members and motivates the exposition of our work into the scientific community.

This paper describes a method, which allows obtaining metallic nanostructures (MN) by focused electron beam irradiation in scanning electron microscope (SEM) in one fabrication step and without the use of additional chemicals. MN-nanodots were obtained by 30kV SEM on surfaces of various metallic thin films (Al, Cr, Cu, Mo, Ag). The thin films were prepared by direct current magnetron sputtering on Si substrate with 500 nm thickness. The size and shape of the obtained MN were measured with atomic force microscope. The height of the nanodots was up to 500 nm and their width at half height was in a range from 100 to 500 nm. The size of the obtained MN depends on the parameters of electron beam and properties of the metal. Possible mechanisms of MN forming under the influence of focused electron beam are discussed.

Our objective was to evaluate rapid eye movements (REMs) associated with visual dream recall in sighted subjects and congenital blind.

During two consecutive nights polysomnographic recordings were performed at subjects home. REMs were detected by visual inspection on both EOG channels (EOG-H, EOG-V) and further classified as occurring isolated or in bursts. Dream recall was defined by the existence of a dream report. The two groups were compared using t-test and also the two-way ANOVA and a post-hoc Fisher test (for the features diagnosis (blind vs. sighted) and dream recall (yes or no) as a function of time).

The average of REM awakenings per subject and the recall ability were identical in both groups. CB had a lower REM density than CS; the same applied to REM bursts and isolated eye movements. In the two-way ANOVA, REM bursts and REM density were significantly different for positive dream recall, mainly for the CB group and for diagnosis; furthermore for both features significant results were obtained for the interaction of time, recall and diagnosis; the interaction of recall and time was however, stronger.

In line with previous findings the data show that blind have lower REMs density. However the ability of dream recall in congenitally blind and sighted controls is identical. In both groups visual dream recall is associated with an increase in REM bursts and density. REM bursts also show differences in the temporal profile. REM visual dream recall is associated with increased REMs activity.

The main goal of this study was to investigate the effect of performing a near task on eye's optical quality.

Wavefront aberrations data of 35 young emmetropic eyes were measured with the L80 Wave+: (1) ocular aberrations were measured with the wavefront sensor, (2) corneal wavefront aberrations were computed from the Placido disk system's data and (3) the internal wavefront component of the eye were determined as the difference between ocular and corneal wavefront aberrations. The measurements were performed before and after a reading task was completed. Several corneal and internal aberration terms changed in opposite directions with the reading task, most of them changing its sign relative to the pre-task condition. The opposite sign between the cornea and the internal optics produced a partial balance that leaved the eye with less aberrations than the individual components. Furthermore, the optical quality of the eye and the retinal image quality changes with a reading task.

Overall optical quality of the eye and its components reduced with the near task, as a consequence of the increase in wavefront aberrations after the reading. The reading task induced a myopic shift of 0.18 D in the distance M value of the emmetropic subjects.

We investigated the interactions between localized plasmons in gold nanorods and excitons in J-aggregates and were able to track an anticrossing behavior of the hybridized modes both in the extinction and in the photoluminescence spectra of this hybrid system. We identified the nonlinear optical behavior of this system by transient absorption spectroscopy. Finally using magnetic circular dichroism spectroscopy we showed that nonmagnetic organic molecules exhibit magnetooptical response due to binding to a plasmonic nanoparticles. In our experiments we also studied the effect of detuning as well as the effect of off- and on resonance excitation on the hybrid states

The visual system takes time to respond to visual stimuli, neurons need to accumulate information over a time span in order to fire. Visual information perceived by the peripheral retina might be impaired by imperfect peripheral optics leading to myopia development. This study explored the effect of eccentricity, moderate myopia and peripheral refraction in temporal visual integration. Myopes and emmetropes showed similar performance at detecting briefly flashed stimuli in different retinal locations. Our results show evidence that moderate myopes have normal visual integration when refractive errors are corrected with contact lens; however, the tendency to increased temporal integration thresholds observed in myopes deserves further investigation.

Organic semiconductor rubrene (C₄₂H₂₈) belongs to most preferred spintronic materials because of the high charge carrier mobility up to 40 cm²(V·s)^-1. However, the fabrication of a defect-free, polycrystalline rubrene for spintronic applications represents a difficult task. We report preparation and properties of rubrene thin films deposited by pulsed laser evaporation of solidified solutions. Samples of rubrene dissolved in aromatic solvents toluene, xylene, dichloromethane and 1,1-dichloroethane (0.23-1% wt) were cooled to temperatures in the range of 16.5-163 K and served as targets. The target ablation was provided by a pulsed 1064 nm or 266 nm laser. For films of thickness up to 100 nm deposited on Si, glass and ITO glass substrates, the Raman and AFM data show presence of the mixed crystalline and amorphous rubrene phases. Agglomerates of rubrene crystals are revealed by SEM observation too, and presence of oxide/peroxide (C₄₂H₂₈O₂) in the films is concluded from matrix-assisted laser desorption/ionization time-of-flight spectroscopic analysis.

A multi-input multi-output (MIMO) algorithm based on higher-order Poincaré spheres is demonstrated for space-division multiplexing (SDM) systems. The MIMO algorithm is modulation format agnostic, robust to frequency offset and does not require training sequences. In this approach, the space-multiplexed signal is decomposed in sets of two tributary signals, with each set represented in a higher-order Poincaré sphere. For any arbitrary complex modulation format, the samples of two tributaries can be represented in a given higher-order Poincaré sphere with a symmetry plane. The crosstalk along propagation changes the spatial orientation of this plane and, therefore, it can be compensated by computing and realigning the best fit plane. We show how the transmitted signal can be successfully recovered using this procedure for all possible combinations of tributaries. Moreover, we analyze the convergence speed for the MIMO technique considering several optical-to-noise ratios.

The optical evaluation carried out using the Inverse Adding-Doubling (IAD) method to determine the scattering and the absorption coefficients of the bioengineered human corneal stromas showed that this type of artificial biomaterials shared many similarities with native control cornea after four weeks of development in culture. Their absorption and reduced scattering coefficients values were higher than the ones of the control cornea, but their spectral behaviors of both coefficients were similar. Time of development in culture was an influencing factor on the results.

We report a Holmium-doped all-fiber laser oscillating in continuous-wave at ~2.05 μm, at in-core pumping by a 1.125-μm laser diode. The active fibers employed are alumino-germano-silicate fibers doped with Ho³⁺ at concentrations of ~1.2×10¹⁹ and ~1.8×10¹⁹ cm^-3. The laser is implemented in non-optimized Fabry-Perot cavity’s geometry, composed of a couple of fiber Bragg gratings with reflectivity of 99 and 90%. When using the lower doped Holmium-doped fiber of proper length (1.4 m), low threshold (~370 mW) and moderate slope efficiency (~13%) of ~2.05-μm lasing were obtained. High-brightness (laser line’s width is ~60 pm) and good noise-to-signal ratio (<0.006) are the laser’s attractivities. In case of the heavier doped fiber of optimal length (1.2 m), the laser output (threshold of ~430 mW, slope efficiency of ~9%, output power of ~9 mW, laser line’s width of 110 pm, noise-to-signal ratio of <0.009) is worse, with a probable reason being deteriorating Ho³⁺ concentration effects.

Retinal image quality measurements (double-pass and Hartmann-Shack) using spatially coherent light sources like lasers or super-luminescent diodes suffer from the presence of speckle in the final images. This well-known phenomenon diminishes the performance of those systems. Although solutions to this problem have been proposed, there still exist room to implement effective methods to face this challenge. We evaluate the influence of changing the polarization states of a laser beam in a double-pass system in order to reduce the speckle noise. By rotating the linear polarization state during the exposure time of the camera the speckle changes and partially averages out. We use the speckle contrast metric to evaluate the performance of the proposed method over experimental results

The optical properties of a tissue or a biomaterial can be described in terms of the absorption coefficient (μ_a), the scattering coefficient (μ_s), the scattering function p(θ,ψ) and the real refractive index of the biomaterial. The Inverse Adding-Doubling, IAD, Method and relationship between the Kubelka- Munk parameters and the transport coefficients are used to describe optical properties at different wavelengths for a large variety of tissues and tissue like biomaterials, such as native cornea, tissue engineered cornea, tissue engineered oral mucosa, natural dentin and dental resin nanocomposites, among others

Self-learning equivalent-convolutional neural structures (SLECNS) for auto-coding-decoding and image clustering are discussed. The SLECNS architectures and their spatially invariant equivalent models (SI EMs) using the corresponding matrix-matrix procedures with basic operations of continuous logic and non-linear processing are proposed. These SI EMs have several advantages, such as the ability to recognize image fragments with better efficiency and strong cross correlation. The proposed clustering method of fragments with regard to their structural features is suitable not only for binary, but also color images and combines self-learning and the formation of weight clustered matrix-patterns. Its model is constructed and designed on the basis of recursively processing algorithms and to k-average method. The experimental results confirmed that larger images and 2D binary fragments with a large numbers of elements may be clustered. For the first time the possibility of generalization of these models for space invariant case is shown. The experiment for an image with dimension of 256x256 (a reference array) and fragments with dimensions of 7x7 and 21x21 for clustering is carried out. The experiments, using the software environment Mathcad, showed that the proposed method is universal, has a significant convergence, the small number of iterations is easily, displayed on the matrix structure, and confirmed its prospects. Thus, to understand the mechanisms of self-learning equivalence-convolutional clustering, accompanying her to the competitive processes in neurons, and the neural auto-encoding-decoding and recognition principles with the use of self-learning cluster patterns is very important which used the algorithm and the principles of non-linear processing of two-dimensional spatial functions of images comparison. These SIEMs can simply describe the signals processing during the all training and recognition stages and they are suitable for unipolar-coding multilevel signals. We show that the implementation of SLECNS based on known equivalentors or traditional correlators is possible if they are based on proposed equivalental two-dimensional functions of image similarity. The clustering efficiency in such models and their implementation depends on the discriminant properties of neural elements of hidden layers. Therefore, the main models and architecture parameters and characteristics depends on the applied types of non-linear processing and function used for image comparison or for adaptive-equivalental weighing of input patterns. Real model experiments in Mathcad are demonstrated, which confirm that non-linear processing on equivalent functions allows you to determine the neuron winners and adjust the weight matrix. Experimental results have shown that such models can be successfully used for auto- and hetero-associative recognition. They can also be used to explain some mechanisms known as "focus" and "competing gain-inhibition concept". The SLECNS architecture and hardware implementations of its basic nodes based on multi-channel convolvers and correlators with time integration are proposed. The parameters and performance of such architectures are estimated.

Photo-Acoustic Microscopy (PAM) has raised high interest in in-vivo imaging due to its ability to preserve the near-diffraction limited spatial resolution of optical microscopes, whilst extending the penetration depth to the mm-range. Another advantage of PAM is that it is a label-free technique – any substance that absorbs PAM excitation laser light can be viewed. However, not all sample structures desired to be observed absorb sufficiently to provide contrast for imaging. This work describes a novel imaging method that makes it possible to visualize optically transparent samples that lack intrinsic photo-acoustic contrast, without the addition of contrast agents. A thin, strongly light absorbing layer next to sample is used to generate a strong ultrasonic signal. This signal, when recorded from opposite side, contains ultrasonic transmission information of the sample and thus the method can be used to obtain an ultrasound transmission image on any PAM.

This work presents an overview of a combined experimental and theoretical analysis on the manipulation of temporal localized structures (LSs) found in passively Vertical-Cavity Surface-Emitting Lasers coupled to resonant saturable absorber mirrors. We show that the pumping current is a convenient parameter for manipulating the temporal Localized Structures, also called localized pulses. While short electrical pulses can be used for writing and erasing individual LSs, we demonstrate that a current modulation introduces a temporally evolving parameter landscape allowing to control the position and the dynamics of LSs. We show that the localized pulses drifting speed in this landscape depends almost exclusively on the local parameter value instead of depending on the landscape gradient, as shown in quasi-instantaneous media. This experimental observation is theoretically explained by the causal response time of the semiconductor carriers that occurs on an finite timescale and breaks the parity invariance along the cavity, thus leading to a new paradigm for temporal tweezing of localized pulses. Different modulation waveforms are applied for describing exhaustively this paradigm. Starting from a generic model of passive mode-locking based upon delay differential equations, we deduce the effective equations of motion for these LSs in a time-dependent current landscape.

The ability to use resonant tunneling diodes (RTDs) as both transmitters and receivers is an emerging topic, especially with regards to wireless communications. Successful data transmission has been achieved using electronic RTDs with carrier frequencies exceeding 0.3 THz. Specific optical-based RTDs, which act as photodetectors, have been developed by adjusting the device structure to include a light absorption layer and small optical windows on top of the device to allow direct optical access. This also allows the optical signal to directly modulate the RTD oscillation. Both types of RTD oscillators will allow for seamless integration of high frequency radio and optical fiber networks.

We have designed a spectrally resolved interferometer to measure the refractive index of transparent samples over a wide spectral band from 400 to 1550 nm. The measuring device consists of a Michelson interferometer whose output is analyzed by means of three fiber spectrometers. The first one is a homemade prism spectrometer, which obtains the interferogram produced by the sample over 400 to 1050 nm; the second one is a homemade transmission grating spectrometer thought to measure the interferogram in the near infrared spectral band from 950 to 1550 nm; the last one is a commercial Czerny-Turner spectrometer used to make high precision measurements of the displacement between the Michelson mirrors also using white light interferometry. The whole system is illuminated by a white light source with an emission spectrum similar to black body. We have tested the instrument with solid and liquids samples achieving accuracy to the fourth decimal on the refractive index after fitting it to a Cauchy formula

In this work, an optical fiber sensing network has been developed to assess the impact of different environmental conditions on lithium batteries performance through the real time thermal monitoring. The battery is submitted to constant current charge and different discharge C-rates, under normal and abusive operating conditions. The results show that for the discharge C-rate of 5.77C, the LiB under cold and dry climates had 32.5% and 27.2% lower temperature variations, when compared with temperate climates, respectively. The higher temperature shift detected in the temperate climate was related to the battery better performance regarding discharge capacity and power capabilities.

In this paper, digital holographic interferometric microscope (DHIM) in conjunction with Fresnel reconstruction method is demonstrated for phase contrast imaging of red blood cells (RBCs). The advantage of using the DHIM is that the distortions due to aberrations in the optical system are avoided by the interferometric comparison of reconstructed phase with and without the object.

In this work we propose a complete characterization method for supersonic gas flow. The optical phase of fringe patterns acquired in a simple Mach Zehnder interferometer is extracted with a differential phase evaluation method based on Fourier Transform (without translation to the frequency origin); reducing the computation steps and decreasing the errors due to the unwrapping process. Optical phase, gradient and Laplacian maps obtained allow detailed analysis of the pressure distribution, and shock wave patterns. We optimize phase evaluation process by studying and comparing effects of four different bandpass filters on phase maps by using quality maps as estimator.

A Fabry-Perot air bubble microcavity fabricated between a section of single mode fiber and a multimode fiber is proposed. The study of the microcavities growth with the number of applied arcs is performed. The sensors are tested for lateral load and strain, where sensitivities of 0.32 nm/N and 2.11 nm/N and of 4.49 pm/με and 9.12 pm/με are obtained for the 47 μm and 161 μm long cavities, respectively. The way of manufacturing using a standard fusion splicer and given that no oils or etching solutions are involved, emerges as an alternative to the previously developed air bubble based sensors.

A new type of polymer and silica connection is proposed. A tapered SMF-28 silica optical fiber tip is fabricated using a CO₂ laser by focusing and stretching the fiber. The tapered silica tip is inserted in one of the holes of a microstructured polymer optical fiber using a 3D alignment system. Using a supercontinuum source, the spectrum is observed after one and after two connections. The polymer fiber is characterized in curvature while using the previous connection.

This paper presents the amplitude and phase imaging of onion epidermis cell using the self-imaging capabilities of a grating (Talbot effect) in visible light region. In proposed method, the Fresnel diffraction pattern from the first grating and object is recorded at self-image plane. Fast Fourier Transform (FFT) is used for extracting the 3D amplitude and phase image of onion epidermis cell. The stability of the proposed system, from environmental perturbation as well as its compactness and portability give the proposed system a high potential for several clinical applications.

Resonant tunneling diode (RTD) integration with photo detector (PD) from epi-layer design shows great potential for combining terahertz (THz) RTD electronic source with high speed optical modulation. With an optimized layer structure, the RTD-PD presented in the paper shows high stationary responsivity of 5 A/W at 1310 nm wavelength. High power microwave/mm-wave RTD-PD optoelectronic oscillators are proposed. The circuitry employs two RTD-PD devices in parallel. The oscillation frequencies range from 20-44 GHz with maximum attainable power about 1 mW at 34/37/44GHz.

The area of terahertz science and applications has grown dramatically in the last 30 years. Instrumental platforms for THz measurements have also proliferated, and now include laser-based, electronic, opto-electronic, and microwave photonics devices. As the field matured, metrology and standardization have gained focused attention, resulting in an increasing number of publications and a book devoted to the subject. However, these have been primarily focused on photonic-based free-space techniques and their particular demands and issues. This paper presents a brief review of metrology requirements for active THz electronic devices, the available instrumentation, state of the art, and challenges.

Arrays of nanoantennas consisting of plasmonic dipole pairs have been widely used in surface-enhanced Raman spectroscopy (SERS). Fine-tuned structures that can efficiently convert incident electromagnetic energy to excite molecules and provide enhanced detection. However, this tuning mechanism also has its disadvantages. In order to prevent the cross coupling, the distance between each individual element must be increased. This leads to low packing density values which in turn results in a reduction of the overall enhanced Raman signal when these structures are compared to broadly tuned aggregates of particles such as those obtained through metal sputtering or colloidal deposition. In this work we demonstrate through simulations and experimental work that it is possible to increase the reflected signal of an array of nanoantennas by reducing the distance between them in the direction both perpendicular and parallel to the orientation of the incident electric field. It is shown the resonant wavelength shifts in two different spectral directions depending in how the intercell distance was reduced. These resultant shifts can reduce the tuning capabilities of the structures but also can increase the SERS intensity due to close coupling of the dipole pairs. We believe that these results will enable the design and fabrication of structures possessing a greater degree of tunability together with an overall enhanced Raman signal that can rival aggregated SERS substrates.

We develop a new avenue to creating the optical spectrometer for the Guillermo Haro astrophysical observatory (Mexico), which combines specifically progressed prism spectrometer with modern acousto-optical approach in the frame of a joint instrument. This schematic arrangement includes two principal novelties. First, we exploit recently developed acousto-optical nonlinearity of the two-phonon light scattering in crystals with linear acoustic losses, which admits an additional physical degree of freedom. This effect allows us to use nonlinear acousto-optical effect for linear processing of optical signals in parallel regime within all the visible range. Similar effect is based on the possibility for tuning the frequency of elastic waves and admits the nonlinear apodization improving the dynamic range. Secondly, we are using the cross-disperser technique with acousto-optical processing for the first time to our knowledge. Additionally, the acousto-optical spectrometers can provide almost 100% efficiency in the acousto-optical interaction in the optimized regime. In the case of 4% Mg doped LiNbO₃ crystal the absorption edge can be shifted down to 370 nm for limited intensity of incoming light. The observation window of optical spectrometer in that observatory is ~ 9 cm, so that the theoretical estimations of maximal performances for a low-loss LiNbO3-crystal for this optical aperture at 405 nm give the spectral resolution 0.0523 Å, resolving power 77,400, and number of spots 57,500. The illustrative proof-of-principle experiments with available for us 6-cm LiNbO₃-crystal have been performed and demonstrated the spectral resolution 0.0782 Å at 405 nm and resolving power 51,790.

Recently, industrial trends strongly favor the concepts of high density, low power consumption and low cost applications of Datacom and Telecom pluggable transceiver modules. Hence, thermal management plays an important role, especially in the design of high-performance compact optical transceivers. Extensive care should be taken on wavelength drift for thermal tuning lasers using thermoelectric cooler and indeed, accurate expression is needed to describe transient characteristics of the Peltier device to achieve maximum controllability. In this study, the exact solution of governing equation is presented, considering Joule heating, heat conduction, heat flux of laser diode and thermoelectric effect in one dimension.

Permanent Bragg wavelength tuning of polymer optical fibre Bragg grating (POFBG) at longer wavelengths has been demonstrated for the first time utilising the thermal annealing process. In general, exposing the polymer material above its β-transition temperature, the fibre shrinks in length, the Bragg grating period becomes shorter and the Bragg wavelength shifts permanently to shorter wavelengths. In this work, a positive tuning of Bragg wavelength has been shown to be feasible when the polymer fibre is stretched during its thermal exposure. The results show that the degree of Bragg wavelength tuning strongly depends on the applying fibre strain or equivalently stress. The work presented in this paper can be used to multiplex POFBGs at any desirable wavelength.

A novel compact and multiband polarization beam splitter based on a dual-core transversally chirped microstructured optical fiber is proposed and analyzed, using finite element method. The results show that the ≈2.9 mm-long polarization splitter can reach an extinction ratio lower than -20 dB in two bands at 1140 nm and 1556 nm. The bandwidths of both bands are 11.7 nm and 47.2 nm respectively. This work analyzes the operation of the device when it is subjected to curvature, finding that it is possible to tune the operating bands. Numerical calculation indicates that this novel structure may find application in telecommunications, because it is capable of working at different wavelength ranges.

OLEDs for lighting became of high relevance, although challenges in the uniformity and thermal effects. In this work, White-OLEDs with 16 cm² emitting area was made with wide color temperature range (3200 K to 10500K) and color rendering index near 90. The CIE coordinates are stable with applied voltage. Thermal images shows 60°C in the center decreasing to 35°C at the border. This effect was study by a scalar electro-thermal model, considering the substrate, electrodes and organic layers. The thermal changing ratio in the series resistance and forward voltage obtained was of - 70 mΩ/°C and -10 mV/°C respectively.

We present several joint transform correlator (JTC) architectures for nonlinear images encryption, decryption and authentication systems. These JTC architectures are developed in different processing domains, such as Fourier, Fractional Fourier, Fresnel and Gyrator domains. Some of these processing domains can add new security keys in order to improve the security of the images encryption, decryption and authentication systems. In this work, we review and present recent nonlinear modifications of encryption decryption and authentication systems based on JTC architecture that allow to significantly increase the quality of the retrieved image after information decryption, and to achieve a high security level against a variety of system attacks.

In this work, we present a new design of a low loss and high birefringence THz Photonic Crystal Fiber (PCF) made of TOPAS material, featuring a porous core with elliptical holes. The full-vector finite element method was employed to analyze the optical properties such as birefringence, confinement losses, and effective material losses; as well as to study how these parameters are dependent on the geometry of the structure. The simulation results showed confinement losses ≈ 0.06 dB/m when a configuration with high grade of porosity in the core was implemented. At the same time, birefringence values close to 3×10^-2 there were obtained. The proposed design can be fabricated easily using standard stack and draw technique and be used in several applications in the THz region to propagate the radiation.

Detection and measurement of low frequency, out-of-plane vibrations play a very important role in several metrological applications. Classical interferometry is well suited for measuring small amplitudes of vibrations, ranging from picometers up to micrometers, but its use is limited to a laboratory environment. Here we consider the Talbot effect and the so-called adaptive photodetectors based on the non-steady-state photo-electromotive force effect for the measuring of low frequency, out-of-plane of vibrations of flat objects with rough surfaces and with amplitudes of vibrations in the order of microns. The adaptive photodetectors produce an electrical current proportional to the square of the visibility of the vibrating intensity pattern impinging on them. In the method here proposed, the vibrating object with rough surface is illuminated with a beam diffracted by a grating (a Ronchi grating), the light reflected by the object is collected by a lens and imaged on to a home-made GaAs adaptive photodetector. The electrical current from the adaptive photodetector is proportional to the instantaneous position of the vibrating object; this signal is monitored and measured with an oscilloscope connected to a lock-in output. The method is very robust and adequate for environments subjected to perturbations and presents the possibility of adjusting its dynamical range by modifying the period of the grating employed. Experimental results that verify our proposal are presented.

We describe a potential prototype of modern spectrometer based on acousto-optical technique with three parallel optical arms for analysis of radio-wave signals specific to astronomical observations. Each optical arm exhibits original performances to provide parallel multi-band observations with different scales simultaneously. Similar multi-band instrument is able to realize measurements within various scenarios from planetary atmospheres to attractive objects in the distant Universe. The arrangement under development has two novelties. First, each optical arm represents an individual spectrum analyzer with its individual performances. Such an approach is conditioned by exploiting various materials for acousto-optical cells operating within various regimes, frequency ranges, and light wavelengths from independent light sources. Individually produced beam shapers give both the needed incident light polarization and the required apodization for light beam to increase the dynamic range of the system as a whole. After parallel acousto-optical processing, a few data flows from these optical arms are united by the joint CCD matrix on the stage of the combined extremely high-bit rate electronic data processing that provides the system performances as well. The other novelty consists in the usage of various materials for designing wide-aperture acousto-optical cells exhibiting the best performances within each of optical arms. Here, one can mention specifically selected cuts of tellurium dioxide, bastron, and lithium niobate, which overlap selected areas within the frequency range from 40 MHz to 2.0 GHz. Thus one yields the united versatile instrument for comprehensive studies of astronomical objects simultaneously with precise synchronization in various frequency ranges.

To date, there is no assessment of more than one survey used for a clinical research study that address subjects with and without symptoms related to accommodative or binocular vision disorders. Thus, the purpose of this study was to investigate two different surveys – CISS and Conlon for the same subject group and analyse also critical visual function parameters. Monocular and binocular accommodative response for 20 subjects was measured for dominant eye with openfield infrared autorefractometer (Shin-Nippon SRW-5000) at three distances (24 cm, 30 cm and 40 cm). Subjects were divided into symptomatic and asymptomatic group using cut off score 21 for CISS and 20 for Conlon survey. We found positive exponential growth relationship between CISS and Conlon scores (R² = 0.7), but separation between symptomatic and asymptomatic group differed significantly depending on which survey was used. We found positive correlation between Conlon score and exophoria at 30 cm (r=0.41, p=0.01) and 24 cm (r=0.27, p=0.03). Relationship between subjective symptoms and following clinical parameters - accommodation lag (r < 0.2, p < 0.05), positive relative accommodation (r < 0.15, p < 0.05) and convergence near point (r = 0.26, p < 0.05) were not significant. Our results confirmed that using different subjective symptom surveys can provide different results within the same subject group, therefore we recommend to use surveys as a part of case history and tool to measure patient satisfaction and results of treatment effectiveness instead of using them for clinical trials as a criteria to divide symptomatic and asymptomatic group.