This PDF file contains the front matter associated with SPIE Proceedings Volume 8412, including the Title Page, Copyright information, Table of Contents, Introduction, and Conference Committee listing.

We discuss and demonstrate the dependence of noise on the signal in time-domain optical coherence tomography (TDOCT). We then derive a depth-dependent matched filter to maximize the signal-to-noise ratio at every pixel in a depth scan (A-scan). We use an empirical estimate of the second order statistics of the noise in OCT images of vascular tissue to implement a depth-dependent filter that is matched to these images. The application of our filter results in an average increase of signal-to-noise ratio of about 7 dB compared to a simple averaging operation. Our filter is not specific to time-domain OCT, but it is applicable to other types of OCT systems.

The hemodynamic responses to 4-aminopyridine (4-AP) induced focal epileptic spikes and electrical stimulations are compared in a rat model. Nonlinearities are quantified with biophysical models. Supranormal oxygen consumption from epileptic spikes is inferred. In one recording, interictal spikes followed an almost periodic pattern. Such rhythmic spiking is a well-documented phenomenon in electrophysiological studies, but the hemodynamics correlates have been less studied. Spikes occurred every 12.5 ± 1.0 s. Peaks in total hemoglobin (HbT), a proxy for regional cerebral blood volume, followed spikes by 2.6 ± 0.3 s. Troughs in HbT preceded spikes by 1.68 ± 1.2 s. The narrowness of this distribution is surprising. From it, one may derive a significant but paradoxical fall in HbT several seconds before the spikes, but which this decrease in HbT is better interpreted as being due to the interictal spike that occurred before.

Atherosclerotic coronary artery disease continues to be one of the major causes of mortality. Prevention, diagnosis and treatment of atherosclerotic coronary artery disease are dependent on the detection of high risk atherosclerotic plaque. As age is one of the most important risk factors, atherosclerosis worsens steadily with increasing age. Automatic characterization of atherosclerotic plaque using the optical coherence tomography (OCT) images provides a powerful tool to classify patients with high risk plaque. In this study we develop an automatic classifier to detect atherosclerotic plaque in young and old Watanabe heritable hyperlipidemic (WHHL) rabbits, using OCT images without reliance on visual inspection. Our classifier based on texture analysis technique may provide an efficient tool for detecting invisible changes in tissue structure. We extracted a set of 22 statistical textural features for each image using the spatial gray level dependence matrix (SGLDM) method. An optimal scalar feature selection process was carried to select the best discriminating features that employ the Fisher discriminant ratio (FDR) criterion, and cross correlation measure between the pairs of features. Using these optimal features, we formed a combination of 5 best classification features using an exhaustive search method. A combined feature set was finally employed for the classification of plaque. We obtained correct classification rate and validation of 76.67% and 75% respectively.

Conventional methods for cervical cancer screening usually employ microscopic observations that may require fluorescence labeling of the cells, which could be time-consuming and expensive. Development of a novel method for cervical cancer cells determination in a rapid, label-free manner may significantly improve the cervical cancer screening technique. Here two-dimensional (2D) light scattering patterns are obtained from yeast cells on a CMOS chip, where laser light is used to excite single cells via fiber-coupling under a microscope. Good agreements between the experimental and Mie theory simulation results convey that 2D light scattering patterns from cervical cancer cells may be obtained upon the apparatus developed here. Mie theory simulations on simplified normal and cancerous cervical cells show that side scattering spectrum may be used for cervical cancer cells screening. Future experiments further convincing the 2D light scattering method proposed here may bring up a powerful technique that has profound applications in cervical cancer cell determination.

The purpose of this report is to provide a review of the effects of low-power photo-induced therapy using lasers of different device parameters such as intensity, wavelength, lasing mechanism (i.e., pulsed or continuous) on the production of Adenosine triphosphate (ATP) in mammalian cells. This is a very important research topic as it is suggested in literature that there might be a relationship between the ATP levels and specific diseases. It has been shown that the ATP production was enhanced at wavelengths ranging between 600 nm and 1000 nm (also known as the optical window), in particular at 600nm, 632.8nm, 635nm, 650nm, and 904nm. However, certain experiments showed that the effectiveness of the photo-induced therapy was also dependent on the dosage and the duration of the supplied light. We present the research conclusions drawn from the experiments reported within the last decade, and provide a list of potential medical treatment(s) for patients using visible and near infrared (NIR) light.

Laser speckle analysis has been widely used in imaging of blood flow. Speckle analysis of 2D light scattering patterns from single cells may find opportune parameters for label-free cell classification. 2D light scattering patterns have been obtained experimentally for Jurkat and CB CD34+ cells, and via finite-difference time-domain simulations for these cells, respectively. Cross section scans of the 2D light scattering patterns are carried out at different locations vertically. The number of the bright speckles in the scanned 1D spectra is used for classification of these two kinds of cells. The malignant cancer cells gives more speckle numbers on average in the multi scans of the 2D light scattering patterns, in comparison to the normal cells. The preliminary results show that speckle analysis of 2D light scattering patterns may be useful for label-free cancer diagnosis, such as early cancer screening.

In this study, a hybrid-model imaging system combining fluorescence and ultrasound (US) was investigated with the motivation of providing structural priors towards improvement of fluorescence reconstruction. A single element transducer was scanned over the sample for anatomy. In the fluorescence part, a laser source was scanned over the sample with the emission received by an EMCCD camera. Synchronization was achieved by a pair of motorized linear stages. Structural information was derived from the US images and a profilometry and used to constrain reconstruction. In the reconstruction, we employed a GPU-based Monte Carlo simulation for forward modeling and a pattern-based method to take advantage of the huge dataset for the inverse problem. Performance of this system was validated with two phantoms with fluorophore inclusions. The results indicated that the fluorophore distribution could be accurately reconstructed. And the system has a potential for the future in-vivo study.

In this work, a very simple electrochemical HIV-1 protease biosensor useful for the development of an inexpensive lab-on-a- chip (LOC) device was constructed. The detection mechanism was designed to minimize the complexity either in the recognition receptor immobilization step or during the detection itself. The magnetic self-assembled monolayer of HIV-1 protease substrate peptide was able to detect as low as 10 pg/ml of the protease within 25 minutes with high specificity.

We are presenting cassette as a novel point of care diagnostic device. This device is easy to use, low cost to prepare, high throughput and can analyze several samples at the same time. We first, demonstrate the preparation method of the device. Then, fabrication of the flexible substrate has been presented. The device has been used for detection of the real sample of E.coli bacteria following by colorimetric detection. We have shown that we could detect 30 cfu/ml bacteria and 100 fg/μl of Staphylococous aureus DNA in 1 hr using LAMP amplification technique. This device will be helpful in hospitals and doctor’s office for analysis of several patients’ samples at the same time.

The advent of inexpensive CO₂ laser systems has led to a wide range of demonstrations of microfabricated lab on chip systems built of acrylic. However, there has been little application of these systems to building microfluidics for DNA analysis. In this work we explore the use of CO₂ laser systems for building microfluidics for DNA analysis and relate the artifacts of the fabrication technology to the performance of the system. We show that surface roughness that leads to significant constrictions in the separation channel provides an upper limit of the size of DNA that can be analysed. Below that upper limit, the resolution of the chip is strongly affected by the degree to which the separation channel is exposed to redeposited by-products of the ablation process. We show that by controlling these effects we are reliably able to discern two types of PCR product as a test representative of a real application. By being able to do this is in microfluidic devices the size of a postage stamp we have shown that we can now use CO₂ laser systems for the development of extremely inexpensive diagnostic systems using a rapid prototyping approach.

Biosensing using long-range surface plasmon-polariton waveguides is demonstrated. Current sensor consists of gold straight waveguides (SWGs) embedded in CYTOP with etched microfluidic channels. The sensing platform is capable of detecting analytes with a small mass as well as monitoring the change in refractive index of bulk solutions. Three solutions with different refractive indices were tested for bulk sensitivity: a mixture of Phosphate Buffered Saline (PBS) and Glycerol (7.25% w/w), Distilled/Deionized water and 2-Isopropanol. Protein Bovine Serum Albumin (BSA) was physisorbed on carboxyl-terminated self-assembled monolayer (SAM). A significant change in signal has been observed for these experiments.

Based on an innovative in-vivo optical dosimeter platform developed by scientists at University Health Network, we miniaturized the optical dosimeter in a tiny probe that fits the tip of an optical fiber. The approach consists in a measure of the absorbance change of a sensitive radiochromic material. The increase in absorbance is measured at a single wavelength and the linearly depends on the ionizing radiation dose. For compactness and design reasons, the proposed probe works in a reflective mode. A significant drawback when working with a reflective configuration is that reflections coming from splitter interfaces add to the signal and cause an apparent deviation from linearity. We studied the back reflections coming from a standard splitter and two custom made bifurcated optical fibers assemblies; 1) 7 fibers and 19 fibers. The 7 fibers connected to a 500 μm plastic optical fiber had the lowest reflection of 0.016% which was 3 times less than the 19 fibers and 100 times less than the standard splitter. An appropriate choice of the splitter was then imperative otherwise an under evaluation of the relative absorbance of −30% will happen.

Surface enhanced Raman scattering is a promising technique for high sensitivity analytical applications. However, there are issues which have to be addressed in order to make SERS a reliable technique such as the optimization of conditions for any given analyte, understanding the kinetic processes of binding of the target molecules to the nanostructures and understanding the evolution and coagulation of the nanostructures, in the case of colloidal solutions. The background electrolyte is a very important factor in SERS experiments. Here we report a detailed study of the influence of the addition of different types of electrolytes on the amplitude and kinetics of the SERS signal in silver colloids. Different amino acids and organic dyes were used as test molecules in the concentration range of 10^-8 to 10^-4 M. We found that a new proposed electrolyte containing HCO₃, CO₃, Cl and SO₄ ions provides very high enhancement of Raman signal in organic molecules we studied. The advantages of the composite electrolyte are especially noticeable at low concentration of tryptophan where we observed 10⁸ enhancement of Raman signal, approximately 300 times larger than for the case of commonly used electrolyte sodium chloride.

We have developed a microfluidic cell sorter for mammalian cells expressing intrinsic fluorescent proteins that enables selection of cells with proteins that have enhanced photophysical properties, such as reduced fluorescence photobleaching and/or reversible dark state conversion. Previous ensemble imaging studies have used an acousto-optic modulator (AOM) to provide millisecond pulsed laser illumination for in vivo assays that distinguish reversible darkstate conversion from irreversible photobleaching. However, in the sorter, cells are hydrodynamically focused into a stream, which flows through a series of 4 or 8 line-focused, continuous, 532 nm laser beams, such that each cell experiences a similar millisecond modulated excitation. The amplitude and timing of the fluorescence response from each of the beams are measured by a red-sensitive photomultiplier and analyzed in real time to separately determine initial fluorescence brightness and photobleaching characteristics. In addition, each cell’s flow speed is found from its time of passage through the beams, and if the analysis results are within adjustable limits, a 1064 nm optical trap beam is switched on and moved along an intersecting trajectory at a matching speed, so that the cell becomes deflected by the optical gradient forces towards another exit channel of the microfluidic device. The optical sorting of cells is similar to that demonstrated by others, except that the motion of the trap beam is achieved using a piezo mirror under computer control, rather than an AOM; also, rather than a single-beam brightness measure using a hardwired circuit, a more complex multi-beam analysis is performed in software using the Real-Time module of LabView (National Instruments) on a separate computer to achieve deterministic timing and low latency. The software displays updated statistics of the sort, obtained by counting cells that pass through an extra laser beam in the exit channel. A mixture of cells expressing different proteins was resolved to select those with slowest photobleaching. Cells collected from the instrument were viable and could reproduce.

This paper reports a novel biosensor monolithically integrate optical waveguide into PDMS microcantilever. The sensor consists of buried optical fibers, integrated optical waveguide and horizontal PDMS microcantilever suspended into microfluidic channel. The thin PDMS layer involves microcantilever, microfluidic cannels and optical channels fabricated using soft lithography technique. The thin layer is covered by semi-bonding of a glass slide and a PDMS layer to enable introducing the material of waveguide core into the waveguide channel embedded into PDMS microcantilever. The covering layers are then replaced by other PDMS layers which have hollow features to release the microcantilever for free deflection and to seal microfluidic network. The input and output multimode fibers are horizontally inserted into the optical channels. The light received at the input fiber is conducted through the optical waveguide microcantilever and is delivered to the output fiber. Numerical model is presented to simulate the optical performance of the optical waveguide PDMS microcantilever under fluid flow testing and to find the proper dimensions and waveguide material. The deflection of microcantilever under flow loading distorts the light and causes power loss at the output fiber. COMSOL Multiphysics 3.5 is used to perform fluid structure interaction analysis to assess the cantilever defection due to fluid flow and the optical simulation to estimate the power loss due to cantilever deflection. The proposed biosensor can be used to measure the force within the range of living cell growth force and to be integrated within bio-sensing microdevices to carefully measure the fluid flow rate.

This work presents a preliminary study on an experimental analysis of the lactobacillus bacterial growth in liquid medium with and without the presence of silver nanoparticles. The study aims to quantify the bactericidal effect of nanoparticles. Quantification of bacterial growth at different times was analyzed by spectroscopy UV/visible and laser reflectometry near the critical angle. From these two techniques the best results were obtained by spectroscopy, showing that as the concentration of silver nanoparticles increases, it inhibits the growth of bacteria, it only grows 63% of the population. Regarding Laser Reflectometry, the variation of reflectance near the critical angle is measured in real time. The observed results at short times are reasonable, since they indicate a gradual growth of the bacteria and the stabilization stage of the population. But at long time, the observed results show abrupt changes caused by temperature effects. The bacteria were isolated from samples taken from commercial yougurth, and cultured in MRS broth at pH 6.5, and controlled with citric acid and constant temperature of 32 °C. Separately, silver nanoparticles were synthesized at 3 °C from aqueous solutions of 1.0 mM silver nitrate and chemically reduced with sodium borohydride to 2.0 mM, with magnetic stirring.

In this paper, design of optrodes of photonic optical fiber to a pH sensor with a pH dye is described. The sensor is prepared by immobilizing blue bromophenol, as a pH dye, using sol-gel technique with a photonic optical fiber. The physical principle is based in the absorption of the optrodes of the light from a laser diode as an emitter, and as transducer we use a photoresist for electronic conditioning of the signal.

In this paper, we develop a novel structure and approach of a pure surface Plasmon Polariton (SPP) sensor with fiber Bragg gratings (FBG) in gold coated specially designed H-cross-section fiber. We evaluate its potential for biological sensing applications of the surrounding refractive index (SRI). Pure SPP has almost all its field concentration at the metal-dielectric interfaces and hence, it is highly sensitive to changes in the sensed medium refractive index. This scheme represents an “in-line” optical fiber SPP sensor scheme. Also, it provides larger and more flexible sensing area along its flat side. Simulation results show that the gold layer thickness essentially influences the sensitivity, and the shape of the reflection spectrum. Increasing the gold layer thickness decreases its sensitivity and broadens the spectrum, increasing the FWHM bandwidth. Results show a maximum sensitivity of 230 nm/RIU and maximum figure of merit; defined as the ratio of sensitivity to FWHM bandwidth of the reflection spectrum; of 10952 RIU^-1 (Sensitivity = 230 nm/RIU and FWHM = 2.1 x 10^-5 μm) with gold thickness of 10 nm. In conclusion, the proposed sensor is highly sensitive and free from any moving parts and can be used as bio-chemical sensor.

In this paper, we propose a monolithic optical front-end for soft-decision low-density parity-check (LDPC) decoders based on 112 Gb/s polarization division multiplexed quadrature shift keying (PM-QPSK) coherent detection. The novel front-end is a low complexity and low cost solution with a performance improvement of 6.4 dB over system without the use of coding. The front-end also outperforms the conventional RS(255,239) based codes by 1.3 dB at the BER of 10^-8.

The objective of this research was to investigate the impact of scratches on 40G NRZ optical link transmission and to understand if industry standards on connector scratches are sufficient for 40G applications.

A sample set of twelve optical cable assemblies were prepared and characterized by TE Connectivity. Each assembly was a mated connector pair. The samples were divided into six groups with different levels of polishing scratches applied to vary the Return Loss (RL) at the mating interface. The measured RL across all groups ranged from a minimum of 26 dB to a maximum greater than 80 dB. Experimental links were built based on a 40G NRZ Bit Error rate Tester, EDFA with attenuator, cable assemblies and a fiber (maximum up to 3 km ITU-T G.652.D fiber). Bit Error Rate (BER) curve, Eye diagram, Jitter and Q-factor were measured for all experimental links. We found there was no significant change in any of the measured parameters for the links with different connector assemblies but with the same fiber length of optical link. The 40G NRZ link with multiple cable assemblies (up to 4 samples) and a fiber (1 to 3km) demonstrated significant robustness to the connector scratches.

Silica-on-silicon planar lightwave circuits have a number of advantages including stability and low insertion loss to optical fiber networks. Standard GeO2 doping levels in the waveguide cores lead to a refractive index contrast, n/n, of 0.75%–2%. This range of index contrast requires relatively large bend radii in order to minimize bend losses. This limits the density scaling of these circuits. By using high dopant levels for a Δn/n of 4%, the bend radius can be decreased to less than 1 mm, from which significant gains in optical circuit density can be obtained. In addition, low-loss ring resonators with free spectral ranges of a few tens of gigahertz can be realized, enabling some additional optical signal processing and filtering on that scale. Optical devices with such high dopant levels have been reported by Bellman et al. in 2004 [1] but to the authors' knowledge, no other experimental work on high-delta GeO₂-doped waveguides has been reported since. In this paper, we present experimental measurements on high-delta devices including directional couplers, MMI couplers, Mach-Zehnder interferometers, and ring resonators. Device performance, including propagation loss, bend loss, interferometer contrast ratio and birefringence will be presented. We demonstrate that ring resonators with 40 GHz free spectral range can be fabricated for optical signal processing.

To reduce the cost of wavelength tunable lasers, the structure and fabrication methods of a wavelength tunable laser based on distributed reflectors with deep-submicron slots are proposed. By using a pillar reversing technique, the device is fabricated with standard UV lithography. The features and benefits of reflectors with deep-submicron slots are simulated and explained. As high as 47dB side mode suppression ratio and 50nm tuning range around 1550nm is achieved.

This paper presents a dumbbell shape micro-ring resonator designed for use as a reflective notch filter. Function-ring as a wavelength-selective notch reflector, the device can be used in optoelectronic applications. The device is designed and analyzed using the transfer-matrix method. Fabricated using silicon-on-insulator technology, the dumbbell micro-ring reflector shows a reflective response with a quality factor of ~11,000 and an extinction ratio of 20 dB.

In this paper we propose and analyze a step-index optical fiber design in which normalized frequency, V, remains constant at all wavelengths of interest. Such a fiber would require materials with specific wavelength dependent refractive index profile. Constant-V operation ensures that the effective area becomes wavelength independent. Larger core with higher V ensures that fiber can have larger effective area, high confinement factor, and reasonably lower bendloss. Such fibers will exhibit higher local dispersion, which is desirable for DWDM communications.

Development of large-scale photonic integrated circuits requires an accurate, simple, and space-efficient method for characterizing the optical losses of integrated optical components. Here we present a ring-resonator-based technique for transmission-loss measurement of integrated optical components. Y-branch splitters are used to demonstrate the concept. This measurement techique is based on characterizing the spectral response of a waveguide ring resonator with a number of Y-branches inserted inside the cavity. The measurement accuracy is intrinsically limited by the optical loss of the ring waveguide and is independent of fiber-to-waveguide coupling losses. The devices were fabricated using a CMOS-compatible silicon-on-insulator technology. Our results show that the proposed technique is promising for high-accuracy, high-efficiency characterization of optical losses. Limitations of and potential improvements to the technique are also discussed.

Performance of millimeter-wave (mm-wave) multi-band orthogonal frequency division multiplexing (MB-OFDM) ultrawideband (UWB) signal over fiber transmission system is investigated considering impact of modulation index (MI). Experiments are conducted to verify our theoretical analysis and good agreement is obtained. In this work, we propose an optical frequency quadrupling technique using two cascaded Mach-Zehnder modulators (MZMs) biased at quadrature and driven by the same local oscillator frequency but with 1800 phase shift between the two MZMs. We demonstrate 30GHz mm-wave wireless that carries three-bands OFDM UWB signals, and error vector magnitude is used to analyze the transmission quality. It is found that the EVM decreases from ~-13.63 to -18.9 dB when increasing the LO modulation index (MI) from 66 to ~117%.

This work addresses the problem of inefficient bandwidth utilization in optical telecommunication systems caused by network impairments such as latency, congestion, packet loss ratio and error ratio. The proposed solution is a software based system that implements User Datagram Protocol (UDP), the Java platform and custom designed transmission control mechanisms. The system offers flexibility in configuration, can be deployed over existing telecommunication infrastructure and does not require modifications to the hardware layer of the network infrastructure.

In this work, we propose and investigate a novel modulation technique for the generation of multiple millimeter wave (mm-wave) signals using high-order harmonic generation with a dual-electrode Mach-Zehnder modulator (MZM). The laser output is split into two branches by the use of a polarization beam splitter. We use polarization multiplexing to avoid the inter-symbol interference between multiple mm-wave signals. The proposed technique is comprised of two parallel MZMs. As an example, we consider an RF₁ at 7.5 GHz and RF₂ at 8.125 GHz, each of which carries its own data signal and drives each MZM, respectively; and mm-wave signals at 30 GHz and 32.5 GHz, i.e. a frequency quadrupler, are obtained after photomixing. The performance of the system is evaluated in terms of Q-factor. Simulation results show that data signal at 625 Mb/s is successfully transmitted over 50 km of single mode fiber. The generated mm-wave signal is robust to chromatic dispersion.

Polarization-multiplexed optical signals require that the birefringence of optical devices be controlled. Birefringence in silica-on-silicon waveguides emerges from a combination of form birefringence and stress birefringence, both of which can be affected by the core dopant distribution in the case of rectangular-core waveguides. In this paper, we present a numerical and experimental study of the effect of dopant diffusion on waveguide modal birefringence. In the numerical study, modal birefringence is calculated with a finite element model that includes thermal stress effects. The effect of diffusion on form birefringence and stress birefringence will be illustrated. It will be shown that the initial index step of the waveguide has an influence on the evolution of the modal birefringence as a function of diffusion. In the experimental study, measurements of the phase and group birefringence will be presented as a function of waveguide width for waveguides with thermally diffused cores. It will be shown that thermal diffusion can be used for birefringence control of rectangular waveguides.

Antibiotics are extensively used in veterinary medicine for the treatment of infectious diseases. The use of antibiotics for the treatment of animals used for food production raised the concern of the public and a rapid screening method became necessary. A novel approach of detection of antibiotics in milk is reported in this work by using an immunoassay format and the Localized Surface Plasmon Resonance property of gold. An antibiotic from the penicillin family that is, ampicillin is used for testing. Gold nanostructures deposited on a glass substrate by a novel convective assembly method were heat-treated to form a nanoisland morphology. The Au nanostructures were functionalized and the corresponding antibody was absorbed from a solution. Solutions with known concentrations of antigen (antibiotics) were subsequently added and the spectral changes were monitored step by step. The Au LSPR band corresponding to the nano-island structure was found to be suitable for the detection of the antibody antigen interaction. The detection of the ampicillin was successfully demonstrated with the gold nano-islands deposited on glass substrate. This process was subsequently adapted for the integration of gold nanostructures on the silica-on-silicon waveguide for the purpose of detecting antibiotics.

There is considerable interest in Long-Range Surface Plasmon-Polariton (LRSPP) waves, which inherently have a low attenuation, for sensing applications. LRSPPs propagating along thin metal stripes arranged as integrated optical structures, such as Mach-Zehnder interferometers (MZIs), are or particular interest for biosensing. In order for sensors to be functional, high-quality metal stripe waveguides integrated with microfluidic channels are required. Wafer-based fabrication processes have been developed and implemented to fabricate thin (35 nm) Au stripes and features embedded into CYTOP claddings, with etched microfluidic channels exposing sections of the stripes for sensing. CYTOP is a fluoropolymer having a refractive index close to that of water, motivating its use as a cladding material. The fabrication processes developed are discussed and measurements (physical and optical) on operating sensors are presented.

In this project the viability of an optically-enhanced chassis providing n × 10 Gbit/s bandwidth for both point-to-point and broadcast communication between servers is determined.

Athermal operation of silicon waveguides for the TM and TE mode is achieved using the bridged subwavelength grating (BSWG) waveguide geometry. For the TM mode the experimental results show that the temperature-induced wavelength shift (dλ/dT) is an order of magnitude smaller for the BSWG waveguides with grating duty cycle, waveguide and bridge widths of 42%, 490 nm and 220 nm, respectively, as compared to standard photonics wires (PW). For the TE mode similar results are achieved by using the bridge width of 200 nm and similar duty cycle and waveguide width. A temperature-induced shift of only -2.5 pm/°C is reported for the TM polarized light. Propagation losses of BSWG waveguides for both polarizations were measured to be about 8 dB/cm, comparable to that of PWs.

A process for joining optical materials by direct bonding reinforced by femtosecond laser welding is presented. It is suitable for assembly of components for aerospace and high power laser applications where adhesives must be avoided. Joining is realized in two steps. Firstly, materials are direct bonded so as to achieve a state of optical contact preferably over the whole area between bonded surfaces. The second step consists in sealing the direct bonded region by writing weld lines by femtosecond laser pulses at the outskirts of the bonding surface. The bond, applicable to both similar and dissimilar material combinations, is resistant to important mechanical and thermal constraints and does not alter the assembly’s optical transmission properties inside the sealed area. Most importantly, the drawbacks of common joining methods are avoided, such as premature aging, degassing, photo-bleaching and limited applicable material combinations.

High intensity femtosecond laser pulses can be used to generate X-ray radiation. In the laser wakefield process, when a high intensity laser pulse (<10¹⁸ W/cm²) is focused onto a gas jet target, it interacts with the instantaneously created under-dense plasma and excites a wakefield wave. In the wakefield electrons are trapped and accelerated to high energies in short distances. The electrons trapped in the wakefield can perform Betatron oscillations across the propagation axis and emit X-ray photons. The Betatron X-ray beam is broadband as the radiation emission has a synchrotron distribution. The X-ray beam is collimated and its pulse duration is femtosecond. For high resolution and phase contrast X-ray imaging applications, the important feature of the X-ray Betatron beam is the μm source size. Using ALLS 100 TW class laser system we demonstrate that the Betatron X-ray beam is both energetic and bright enough to produce single laser shot phase contrast imaging of complex objects located in air.

The design of gratings for broadside coupling of a Gaussian beam to a long-range surface plasmon polariton (LRSPP) waveguide is explored. The waveguide is a gold (Au) slab supported by a thin Cytop membrane bounded by air and forms a waveguide structure for potential use as a gas sensor. Grating coupler designs are proposed and modeled in two dimensions using the finite element method (FEM). A large design space of varying grating dimensions and input positions is examined and the resulting simulations predict an input coupling efficiency of approximately 29%. Fabrication of these gratings is also examined through standard optical lithography.

We introduce a memory efficient approach for the reduction of the required memory storage in time domain transmission line modeling (TLM)-based adjoint variable method (AVM). The proposed approach is based on manipulating the TLM scattering matrices to remove all redundant calculations. The required memory overhead for our approach is drastically reduced to only 10% of that of the original TLM-based AVM. This represents the ultimate memory reduction preserving the same accuracy of previously reported AVM approaches. Utilizing this approach, we can conduct AVM calculations for dielectric bulk structures 10 times larger. Our algorithm has been verified by comparison to the expensive finite difference approaches.

Successful trials have been made through a designed algorithm to quantize, compress and optically encode unsigned 8 bit integer values in the form of images using nano optical features. The periodicity of the nano scale features (nano gratings) have been designed and investigated both theoretically and experimentally to create distinct states of variation (three on state and one off state). The benefits of using a 4 state unit information carrier is been investigated through transmission models of non ergodic and ergodic signals. A thorough investigation has targeted the effects of the use of multi-varied state nano optical features on data storage density and consequent data transmission rates.

We propose a novel approach for efficient design of large number of coupled microcavities. This approach is based on formulating the design problem as an convex optimization problem. This formulation allows for fast, efficient solution of the desing problem. A filter design using 150 coupled microcavities has been achieved in less than one second of simulation using personal computer. The proposed technique require no initial desing to start the optimization process.

Multimode Interference (MMI) device is a useful optical component for optical power splitter/combiner and router applications. In this paper we present high precision calculation results on the optimum position of self-images in an MMI and their variation due to wavelengths, for WDM applications. We show that the commonly used MMI self-image position calculation methods, using the beat length of two lowest order modes or effective MMI width approximation, lead to significant deviations from the optimum self-image position. We calculate the optimum position of the self-image by finding the maximum value of overlap integral of total MMI field, comprised of all MMI modes, with the total field at the input of the MMI device. In addition, for the optimum output power coupling distance for MMI, we calculate the overlap integral of the total MMI field with the output waveguide field. Both these methods give approximately the same optimum length. We obtain up to 60 um difference in optimum self-image position for a Si MMI (width =15 ~ 30 um), and refractive index difference of 0.02 between core and cladding, from the approximations based methods. We also calculate the variation of this image position in 1.50 um to 1.60 um wavelength region. We show that the optimum image position is strongly dependent on wavelength, with up to 100 um variations in this wavelength range. In addition, we show that there is a significant variation in this self image position with MMI widths, at points where a new power carrying mode is added.

Optical fields that are periodic in the transverse plane self-image periodically as they propagate along the optical axis: a phenomenon known as the Talbot effect. A transfer matrix may be defined that relates the amplitude and phase of point sources placed on a particular grid at the input to their respective multiple images at an image plane. The free-space Talbot effect may be mapped to the waveguide Talbot effect. Applying this mapping to the transfer matrix enables the prediction of the phase and amplitude relations between the ports of a Multimode Interference (MMI) coupler– a planar waveguide device. The transfer matrix approach has not previously been applied to the free-space case and its mapping to the waveguide case provides greater clarity and physical insight into the phase relationships than previous treatments. The paper first introduces the underlying physics of the Talbot effect in free space with emphasis on the positions along the optical axis at which images occur; their multiplicity; and their relative phase relations determined by the Gauss Quadratic Sum of number theory. The analysis is then adapted to predict the phase relationships between the ports of an MMI. These phase relationships are critical to planar light circuit (PLC) applications such as 90° optical hybrids for coherent optical receiver front-ends, external optical I-Q modulators for coherent optical transmitters; and optical phased array switches. These applications are illustrated by results obtained from devices that have been fabricated and tested by the PTLab in Si micro-photonic integration platforms.

Numerical simulation of the interaction between light and tissue is important for the design and analysis of many optical imaging modalities. Most current simulations are based on the Transport Theory of light in a dielectric, and only calculate the intensity of light in a volume. These simulations do not provide phase information, which is important for many biomedical imaging systems. We are interested in obtaining the optical field, magnitude and phase, due to the interaction of light with tissue. Therefore, we need to solve the integral equation for scalar scattering in a volume of interest. Since the wavelength of light is in the order of nanometres, simulation of volumes of more than a few millimetres requires intensive computational resources. For large volumes, Monte Carlo methods are a suitable choice because their computational complexity is independent of the mathematical dimension of the problem. Also by a careful selection of the random sampling scheme the number of samples needed can be further reduced. In this paper we present an implementation of a method to solve Fredholm integral equations of the second kind using Reversible Jump Markov chain Monte Carlo (RJMCMC). This method could be used to simulate light in tissue with very large electrical size, meaning tissue whose physical dimensions are much larger than the wavelength of light, by solving the integral equation of scalar scattering over a large domain. We implemented this method based on RJMCMC and present in this paper the results of applying it to solve integral equations of one and two dimensions.

In this work, we numerically study the effect of high-orderλ /4 phase-shift grating in laterally-coupled distributed feedback (LC-DFB) lasers performance. It is well known that single-mode operation is improved by introducing λ/4 phase-shift grating in conventional DFB lasers. However, introducing λ/4 phase-shift region increases the optical intensity around this region and results in strong longitudinal spatial-hole burning (LSHB). To flatten the longitudinal carrier density distribution, we have numerically studied the effect of the radiation modes on high-order LC-DFB lasers using a modified time-domain travelling-wave algorithm. It is shown that, the degree of LSHB can be effectively reduced when considering high-order LC-DFB lasers with grating duty-cycle tailored to optimal values. LC-DFB laser cavity with high-order grating shows a strong non-uniformity of the carrier density distribution. However, as we finely engineer grating features, LSHB is highly reduced and high single mode suppression ration can be achieved.

Optical systems generally require a high level of optical components positioning precision resulting in elevated manufacturing cost. The optomechanical tolerance analysis is usually performed by the optomechanical engineer using his personal knowledge of the manufacturing precision capability. Worst case or root sum square (RSS) tolerance calculation methods are frequently used for their simplicity. In most situations, the chance to encounter the worst case error is statistically almost impossible. On the other hand, RSS method is generally not an accurate representation of the reality since it assumes centered normal distributions. Moreover, the RSS method is not suitable for multidimensional tolerance analysis that combines translational and rotational variations. An optomechanical tolerance analysis method based on Monte Carlo simulation has been developed at INO to reduce overdesign caused by pessimist manufacturing and assembly error predictions. Manufacturing data errors have been compiled and computed to be used as input for the optomechanical Monte Carlo tolerance model. This is resulting in a more realistic prediction of the optical components positioning errors (decenter, tilt and air gap). Calculated errors probabilities were validated on a real lenses barrels assembly using a high precision centering machine. Results show that the statistical error prediction is more accurate and that can relax significantly the precision required in comparison to the worst case method. Manufacturing, inspection, adjustment mechanism and alignment cost can then be reduced considerably.

A silicon racetrack resonator modulator, based on phase-match control, is proposed. The device is comprised of a straight waveguide evanescently coupled to a ring resonator in the shape of a racetrack. A PN junction, formed in the straight waveguide, is used to control the degree of phase-match in the coupler. Consequently, the coupling, and hence the power transmission, is controlled by the voltage across the PN junction. The predicted free spectral range and switching voltage are, respectively, 0.4 nm and 7.5 Volt, while the device dimensions are approximately 0.7 mm by 0.15 mm. The device behavior is analyzed using two different analytic approaches for the coupling, the results of which are compared to numerical simulations.

It is well known that an appropriate apodization of the light beam within acousto-optical data processing makes it possible to increase the potential dynamic range of a system up to 40 dB and more. Customary, the Gaussian apodization is used when a light beam incidents on a rectangular uniform operative aperture of acousto-optical cell. However, modern acousto-optics exploits often rather high-frequency radio-wave signals in a view of increasing the frequency bandwidth by itself or/and growing the time-bandwidth product inherent in a cell. Anyway, similar acoustooptical cells operate with such frequencies that acoustic losses become already pronounced, so that the effect of these losses along an aperture of a cell has to be taken into account. Typically, acceptable level of the acoustic losses accounts about 3 − 6 dB per cell’s aperture. By this it means that the expected no-uniformity of distributing the acoustic energy is now not negligible. To obtain really optimized profile of the incident light beam apodization the expected influence of acoustic losses ought to be analyzed and estimated. In connection with aforementioned no-uniformity or asymmetry, one can propose exploiting a quasi-Gaussian profile of the incident light beam reasonably shifted relative to the center of an aperture of the acousto-optical cell with appreciable acoustic losses.

We present a study of gold nanopyramids and their optical properties. A comparison with the extinction properties of gold nanorods and nanocubes is also undertaken. The Finite Difference Time Domain (FDTD) method is used for the study of optical properties. The nanopyramids display a dual plasmon resonance when excited with a perpendicularly polarized signal due to the excitation of dipole and quadrupole modes. The quadrupole modes are not strongly affected by changing the height of the nanopyramids whereas the dipole mode is redshifted with increasing the height of the nanopyramids. The quadrupole mode could be of interest in some applications where the shorter wavelength resonance is desired. The quadrupole and dipole modes are located at 620 nm and 765 nm respectively. This band is used for both intensity and wavelength modulated biosensors. Furthermore, the electric field is enhanced in the case of the nanopyramids which is considered as another advantage in sensing and surface enhanced Raman scattering (SERS) applications.

Basic performances of the acousto-optical cells, which can be potentially involved into creating a novel triple-product acousto-optical processor for modern astrophysical applications, are under estimation. The main attention is paid to the time-bandwidth product, because just this parameter can be taken as the most general one for the characterization of performance data inherent in each individual cell. Functional capabilities peculiar to the cells operating over either normal or anomalous light scattering regime are under consideration. Evidently, the anomalous regime of light scattering promises better results. Both the theoretical estimations and the experimental data obtained for a large-aperture acousto-optical cell based on a tellurium dioxide crystal, exploiting the anomalous light scattering, gives the time-bandwidth product equal to about 4000 .

This processor is oriented to studies in the extra-galactic astronomy as well as to searching the extra-solar planets, so that algorithm of the space-and-time integrating is desirable for a wideband spectrum analysis with an improved resolution. It includes 1D-acousto-optic cells as the input devices for a 2D-optical data processing. The importance of this algorithm is based on exploiting the chirp Z − transform technique providing a 2D-Fourier transform of the input signals. The system produces the folded spectrum, accumulating advantages of both space and time integrating. Its frequency bandwidth is practically equal to the bandwidth of transducers inherent in acousto-optical cells. Then, similar processor is able to provide really high frequency resolution, which is practically equal to the reciprocal of the CCD-matrix photo-detector integration time. Here, the current state of designing the triple product acousto-optical processor in frames of the astrophysical instrumentation is presented.

The polymer polydimethylsiloxane (PDMS) whose refractive index and shape vary with absorbed organic compounds and pressure is used as the cladding layer in the tapered region of an optical fiber. The light propagation in the tapered region is influenced by the refractive index and shape changes of the PDMS layer due to the optical evanescent field. By monitoring the optical tapered fiber transmission power variations, an organic compound/ pressure sensor is developed.

This paper outlines the design and testing of a digital imaging system that utilizes an artificial neural network with unsupervised and supervised learning to convert streaming input (real time) image space into parameter space. The primary objective of this work is to investigate the effectiveness of using a neural network to significantly reduce the information density of streaming images so that objects can be readily identified by a limited set of primary parameters and act as an enhanced human machine interface (HMI). Many applications are envisioned including use in biomedical imaging, anomaly detection and as an assistive device for the visually impaired. A digital circuit was designed and tested using a Field Programmable Gate Array (FPGA) and an off the shelf digital camera. Our results indicate that the networks can be readily trained when subject to limited sets of objects such as the alphabet. We can also separate limited object sets with rotational and positional invariance. The results also show that limited visual fields form with only local connectivity.

An imager that can measure the distance from each pixel to the point on the object that is in focus at the pixel is described. This is accomplished by a short photoconducting lossi lightguide section at each pixel. The eye or camera lens selects the object point who’s range is to be determined at the pixel. Light arriving at an image point trough a convex lens adds constructively only if it comes from the object point that is in focus at this pixel.. Light waves from all other object points cancel. Thus the lightguide at this pixel receives light from one object point only. This light signal has a phase component proportional to the range. The light intensity modes and thus the photocurrent in the lightguides shift in response to the phase of the incoming light. Contacts along the length of the lightguide collect the photocurrent signal containing the range information. Applications of this camera include autonomous vehicle navigation and robotic vision. An interesting application is as part of a crude teleportation system consisting of this camera and a three dimensional printer at a remote location.

A new type of Raman spectroscopy hyperspectral imager based on Bragg tunable filter has been developed by University of Montreal and Photon etc. The technology of Bragg tunable filter significantly reduces the acquisition time by selecting a single wavelength in a full camera field and scanning the wavelength with a high efficiency. The transmission is continuously tunable over 400 nm range with a spectral resolution of 0.2 nm. We here present the principle of this novel Raman imaging system as well as hyperspectral images of a Si/Ti structured wafer and carbon nanotubes taken with a spectral resolution of 0.2 nm on the whole field of view of the microscope.

Chiral materials possess circular dichroism property that leads to difference in absorption between left and right handed circularly polarized beams. Using these materials in an optical system or measuring their properties causes transmission impairments such as circular dichroism (CD). Using Jones matrix analysis we show the polarization independence in transmission of a chiral element placed in a Sagnac loop interferometer containing a half-wave plate. Keywords: Chiral, circular dichroism, Jones matrix, Sagnac loop interferometer

We report a novel plasmonic solar cell design implemented on an amorphous silicon platform. The enhancement of the scattering and trapping of the light is achieved by embedding nano-metallic cubic particles within the cell’s junction. Amorphous silicon cell with a thickness of 1200nm is used. The spectral absorption of the silicon cell is limited to wavelengths larger than 1.1 u. Our proposed solar cell has a p-i-n configuration, with the amorphous silicon as the photo-active layer. Silver cubic nanoparticles are embedded at different locations within the photoactive layers of the solar cell. With the use of an FDTD simulator, we are able to characterize the optical performance of the solar cell. Our results show that the plasmonic properties of the cubic nanoparticles are more attractive for sensing applications compared to the traditional spherical configuration. The geometry of the cubic nanoparticles enables control over plasmon resonances both in the resonant wavelength and the degree of field enhancement. This is done by improving the refractive-index sensitivity on a thin silicon film, as well as increasing the scattering and trapping of light. Our simulations predict that the silver metallic nanoparticles will enhance the solar cell efficiency, by optimizing the plasmonic properties of the silver nanocube monolayer. We have achieved a 67% increase (from 7.5% to 12.5%) in the cell’s efficiency by adding plasmonics to traditional amorphous p-i-n solar cell.

Different densities of gold nanorods (GNRs) were incorporated on the back electrode of bulk heterojunction organic solar cell (OSC). GNRs layers (1, 3, and 5) were deposited on top of the poly(3-hexylthiophene) (P3HT) and phenyl- C61-butyric acid methyl ester (PCBM) layer using spin-casting technique. According to the optical and structural characterizations, the solar cell devices incorporated with one layer of gold nanorods showed an enhancement in both power conversion efficiency and short-circuit current by up to 14% and 22% respectively as compared to the devices without gold nanorods. This result suggests that GNRs in the back electrode of polymer solar cells act as backscattering elements. They not only increase the optical path length in the active layer but also store energy in localized surface plasmon resonance mode. Both mechanisms lead to enhancement of light absorption and in turn contribute to photocurrent generation and the overall power conversion efficiency. On the other hand, the solar cells with high density GNRs on the back electrode showed inferior performance compared to that of low density integrated ones. The decrease in PCE would stem from enhanced charge recombination induced by high density GNRs. Furthermore, generation of intense local electric fields named hotspots, would reduce the charge transportation and exciton dissociation probability. In such cases, the power conversion efficiency of the device is observed to be less than that for one layer GNRs or even the control device.

An increase in the aspect ratio of silicon platelets grown by Lateral Diffusion Epitaxy (LDE) is achieved. Epitaxial growth is achieved by a compound graphite slider boat in which an oxidized silicon plate is placed above the seed line on the substrate. The function of the plate is to i) favor side wall growth by limiting vertical nucleation on the platelets, and ii) to enhance the surface smoothness by restricting diffusion of silicon to a horizontal direction. We have studied layer growth from the In-Si liquid phase by reducing the gap between substrate and plate. By reducing the gap, it allows for a more uniform growth of silicon from the side wall of the strip. In addition, we investigate repositioning the silicon seed line to a downward orientation. In this case, the diffusion rate increases due to a gravity effect.

In this paper we present extension of electronic speckle pattern interferometry (ESPI) to the long wave infrared range which makes use of CO₂ lasers and digital recording on microbolometer based uncooled thermographic cameras. The measurement range and accuracy of this technique is related to the wavelength of the laser. In visible light ESPI is often not well suited for field applications or for large displacement measurement due to the short wavelength used, which imposes high stability constraints. With wavelengths around 10 micrometers, corresponding to CO₂ lasers, we have a typical 20 factor of decrease of the stability requirements; meantime the range of measurement is increased by the same factor. We will show some important steps for the development of the system and we will give some interesting results obtained in industrial non-destructive testing applications.

Theoretical schemes for laser cooling with nanoparticles have been presented and comprehensively investigated. It is shown that specially designed samples based on nanoparticles can be used to improve the process of laser cooling of solids. One of the proposed schemes is based on lead salt colloidal quantum dots (QDs) doped in a glass host. The second one is based on Tm³⁺ doped oxy fluoride glass ceramic. It has been shown that lead salt colloidal QDs doped in a glass host can operate as artificial atoms. Very short (microsecond range) radiative lifetimes of the excited 1Sh level of PbSe QDs in comparison with the relatively long (millisecond) radiative lifetime of rare-earth (RE) ions allows the cooling process to be accelerated and to use new hosts with relatively high maximum phonon energy, which have so far been considered not suitable for cooling with RE ions. It has been shown that the second sample, which is based on Tm³⁺ doped oxy fluoride glass ceramic provides the unique combination of high chemical and mechanical stability of the oxide glass, which is important for a number of applications, and the low phonon energy of the fluoride nano-crystals, which trap a majority of Tm³⁺ ions participating in the cooling process. This is highly beneficial for laser cooling of solids, since the effective embedding of rare-earth ions in the crystalline phase with low phonon energy provides a high quantum efficiency for the ³F₄ → ³H₆ transition involved in the cooling cycle in the Tm³⁺ ions, which is a key parameter for laser cooling of solids.

Among the multiple techniques proposed to obtain continuous tuning of a laser, many involve a wavelength selective element that needs to be rotated in order to select the output wavelength. Such methods usually require more optical components than the technique proposed in this paper. Our group uses the line spacing variation in a custom-engineered chirped grating to achieve a mode-hop free modification of the output wavelength of a semiconductor laser by a simple translation of the grating. The useful beam out-coupled through the 0th-order is propagating in a constant direction for any tuned wavelength. The variation in the line space also induces a focal effect in the axis perpendicular to the grooves; it is exploited to compensate a part of the beam divergence in the external cavity. Moreover, a transverse focal effect from the holographic grating is introduced for improved reinjection in the laser chip. With this simple configuration, it has been possible to obtain a continuous tuning of a semiconductor laser over 10 nm at an average wavelength close to 1540 nm. The output power of such a laser was near 8 mW and quite stable over all the tuning range. Fine adjustments are still made to obtain a greater tuning range.

Laterally-coupled distributed feedback (LC-DFB) lasers offer compelling advantages over standard DFB lasers. The use of surface grating on the ridge waveguide sidewalls in LC-DFB devices avoids any epitaxial overgrowth. This provides a considerable simplification in the fabrication process, reducing cost and time of manufacturing, and ultimately increasing yield. It offers also the potential for monolithic integration with other devices; paving the way towards low-cost and mass-production of photonics integrated circuits. In this work, we report on the realization of high-order grating InGaAsP/InP multiple-quantum-well (MQW) LC-DFB lasers at 1.55 μm by means of stepper lithography and inductively-coupled reactive-ion as well as wet chemical etching. Third-order rectangular-shaped grating has been lithographically defined on the ridge waveguide sidewalls with a relatively deep etching along the laser cavity. The preliminary experimental characterization shows interesting results for as-cleaved devices tested in room temperature under CW operation. A fabricated 1500 μm-long cavity LC-DFB laser shows stable single-mode operation with a side mode suppression ratio as high as 50 dB. The tested device can emit at power as high as 9 mW, and the measured threshold current is around 80 mA at room temperature. Moreover, the measured linewidth has been found to be as narrow as 178 kHz using the delayed self-heterodyne interferometric technique.

Solid-Core Photonic BandGap Fibers (SC-PBGF) belongs to the family of microstructured optical fibers whereby the cladding is made of high refractive index inclusions as compared to that of the fiber core. In such fibers, light is confined to the core by an anti-resonant mechanism and several high transmission windows separated by high loss regions compose the transmission spectrum. Guiding mechanism is then identical to the one observed in Hollow-Core PBGF (HC-PBGF) except that a solid core can be exploited. Such PBGFs have proven to be good candidates for single-mode high power delivery and for controlling the spectral extension of supercontinuum generation. Mixing different types of resonators in the cladding or mixing PBG with modifed-Total Internal Reection (m-TIR) mechanism also lead to original and more exible fiber designs. Recent developments in the design and realization of Large Mode Area (LMA) and Highly NonLinear (HNL) fibers are presented, including single-mode ring-structured Bragg _bers, LMA fibers exhibiting a fundamental mode with a flat-top profile, and hybrid fibers for supercontinuum generation or frequency conversion.

The strong optical absorption, scattering and local electric field enhancement associated with the longitudinal Surface Plasmon Resonance (SPR) of gold nanorods (AuNRs) have important applications in imaging, sensing, nonlinear optics, thermal therapy and data encoding. The longitudinal SPR mode can be optimally excited only in the NRs that are most aligned with the electric field of a linearly polarized incident light. Thus, in cast polymer based nanorod composite films, where the NRs orientation is random, only a fraction of the embedded NRs is actually usable to the maximal extent for the intended applications. To enhance the degree of alignment of the AuNRs by uniaxial stretching and increase the application efficiency, we have improved the polymer matrix with respect to plastic deformation and designed a suitable drawing device to reduce the fracture risks of the polymer. The resulting nanocomposite film was characterized by Scanning Electron Microscopy (SEM) and by spectroscopy using linearly polarized light in the UV-Visible range. The linear dichroic ratio of the stretched nanocomposite film was calculated based on the ratio of the peak absorbance of the incident light parallelly polarized, to that of the light polarized perpendicularly to the NRs long axes.

In this study, we investigated the effect of substrate temperature on the change in structural and morphological properties of thin film Gallium Arsenide (GaAs) deposited by pulsed laser deposition (PLD) on Silicon (Si) substrate. The growths were conducted at different substrate temperatures (25º C - 600º C). X-ray Diffraction (XRD), Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM) were used to study the crystal structure and surface quality of the films. It was observed that the films were increasingly more crystalline in the (111) orientation and also larger in crystal grain size with increase in substrate temperature 285º C and above. The deposited GaAs films on Si were smooth, dense and free of voids, pinholes and cracks for a wide range of temperature.

In this work we present two experiments as evidence of negative refraction in one dimensional photonics crystals (1D PC). Particularly the porous silicon (p-Si) multilayer structure is used as 1D PC since this structure presents periodic dielectric components with specific refraction indexes and under certain conditions it can abnormally refract the light. In the first experiment we show the negative refraction for two different wavelengths, one in the visible, and the other in the infrared regions of the spectrum. In this experiment we use a fixed incidence angle for a conditioned white light beam and we look for the emerging negative refracted beam. In the second experiment we characterize de negative refraction observed for the same material by varying the incidence angle in a wide range. The obtained results are compared with a theoretic prediction according a model proposed by the authors [1]. We present a brief description of the material production and its properties, as well.

Photonic crystals are artificial structures that have periodic dielectric components with different refractive indices. Under certain conditions, they abnormally refract the light, a phenomenon called negative refraction. Here, we discuss recent theoretical and simulation results that showed that negative refraction could be present near the low frequency edge of at least the second, fourth and sixth bandgaps of a lossless one-dimensional photonic crystals (1DPC) structure. That is, negative refraction is a multiband phenomenon. We also discuss the negative refraction correctness condition that gives the angular region where negative refraction occurs. We compare two current negative refraction theoretical models with recent experimental results. In order to succeed, an output refraction correction is utilized. The correction uses Snell’s law and an effective refractive index based on two effective dielectric constants. We found good agreement between experiment and both theoretical models in the negative refraction zone.

Research nonlinear optical properties of the materials for the fabrication of opto-electronic devices have growth in the last years. Ionics liquids present nonlinear optical properties. In this work we present the results of nonlinear optical properties of four ionic liquids of 1-methylpyrrolidine family, analyzed using a z-scan technique. The results show the difference obtained using or not a chooper for measuring the nonlinearity and the photoinduced lens. Ionic liquids have a negative nonlinearity (self-defocusing) of thermal origin.

Vitreous system based on antimony oxide Sb₂O₃ has been investigated. The influence of MnO substitution on the mechanical and physical properties in the (80-X) Sb₂O₃–20 PbO–X MnO system has been studied. Vickers hardness, density, molar volume, Young modulus, glass temperature transition, infrared and UV transmission spectra depend on the MnO concentration. Crack analysis of the glass surface under indentor deformation shows the tenacity changes according to the MnO concentration.

Two-dimensional (2D) dopant profiling of the active region of THz quantum cascade laser (QCL) devices has been achieved with atomic force microscopy (AFM). Scanning spreading resistance microscopy (SSRM) and scanning capacitance microscopy (SCM) are shown as the two promising AFM techniques for 2D dopant profiling and mapping of dopant concentration for the sub-nanometer regime devices.

Tip-Enhanced Raman spectroscopy is used to probe isolated silicon nanowires and functionalized gold surface with the goal to evaluate the improvements in lateral resolution and surface sensitivity of this method. The setup that involves the combination of and atomic force microscope and a confocal microscope in back-scattering geometry is described together with the optical alignment procedure used to ideally excite the localized surface plasmon of the metallized tip that acts as the nanoprobe. Once aligned, the tip, in feedback with the sample surface, is positioned at a given point and the Raman spectrum is acquired. The sample is then scanned point-by-point and a TERS map is generated for the object or surface of interest. This approach shows an improved lateral spatial resolution for the single silicon nanowires together with relevant information on the induced stress on the nanowire. Last, we show that the proximity of the TERS tip over an ultraflat gold nanoplate functionalized with an azobenzene thiol molecule, largely enhance the vibrational signal from a single monolayer.

In this study, we fabricated highly efficient blue organic light-emitting diodes by designing different emitting layer structures with fluorescent host and dopant materials of 4,4-bis(2,2-diphenylyinyl)-1,10-biphenyl (DPVBi) and 9,10- bis(2-naphthyl) anthracene (ADN) as host materials and 4,4’-bis(9-ethyl-3-carbazovinylene)-1,1’biphenyl (BCzVBi) as a dopant material to demonstrate electrical and optical improvements. Best enhancement in luminance and luminous efficiency were achieved by a quantum well structure and energy transfer between host and dopant materials in device F as of 8668cd/m² at 8V and 5.16 Cd/A at 103.20 mA/cm² respectively. Among the blue OLED devices doped by BCzVBi, device B emits the deepest blue emission with Commission Internationale de l’E´ clairage (CIExy) coordinates of (0.157, 0.117) at 8V.

Optical space switching is an important functionality in dense wavelength division multiplexing (DWDM) optical communication systems, particularly within reconfigurable optical add-drop multiplexers (ROADMs) [1]. Current commercially available ROADMs are based on micro-electromechanical systems (MEMS) or liquid crystal switches but these do not have sufficient switching speed for future network requirements. Power consumption (i.e. energy per switching operation multiplied by switching rate) is a very important parameter in the selection of a switching technology. Space switches based on current injection in silicon have been reported with nanosecond switching speeds and average power consumption on the order of mW [2], which becomes significant if many switches are required in a fabric. Electro-optic (EO) switches, which utilize the Pockels effect in which the refractive index changes when an external voltage is applied [3], only dissipate power when the switch state is changed. Electro-optic switches can be implemented either as non-resonant designs (for example the Mach-Zehnder interferometer (MZI)) or as resonant designs (for example the Fabry Perot interferometer (FPI)). In this study we compare the switching energies of electro optic MZI and FPI switches by considering the capacitance of the switch, which is determined by the length of the active region of the switch. We show that for a non-resonant switch, switching energy increases linearly with device length, regardless of applied voltage, and so is simply determined by the strength of the electro-optic coefficient. We assume that the resonant switch is implemented as a switchable comb filter [4], with a free-spectral range equal to twice the wavelength spacing. This then fixes the interferometer length. As a result the resonant switch has requires significantly less switching energy for the same material parameters and is thus of interest for future ROADM implementations.