April was an extraordinary month for me due to two significant events, both fueled by technology. In one instance, available technology was great and made a big difference in many lives; in the other, technology played a horrible role, and its misuse was unfortunate to a young person very close to me. . I was very proud of the role that technology played in the identification of the suspected Boston Marathon bombers. This was an event that was high profile and highly regarded by most Americans, encompassing the spirit that we all admire. Instead, it was turned into a tragedy by terrorism that killed three people and wounded many more. There are many survivors whose lives will never be the same.

A novel photonic crystal fiber (PCF) having circular arrangement of cladding air holes has been designed and numerically optimized to obtain a bend insensitive single mode fiber with large mode area for both wavelength division multiplexing (WDM) communication and fiber-to-the-home (FTTH) application. The bending loss of the proposed bent PCF lies in the range of 10 ⁻³ to 10⁻⁴ dB/turn or lower over 1300 to 1700 nm, and 2 × 10 ⁻⁴   dB/turn at the wavelength of 1550 nm for a 30-mm bend radius with a higher order mode (HOM) cut-off frequency below 1200 nm for WDM application. When the whole structure of the PCF is scaled down, a bending loss of 6.78×10 ⁻⁴   dB/turn at 1550 nm for a 4-mm bend radius is obtained, and the loss remains in the order of 10 ⁻⁴   dB/turn over the same range of wavelength with an HOM cut-off frequency below 700 nm, and makes the fiber useful for FTTH applications. Furthermore, this structure is also optimized to show a splice loss near zero for fusion-splicing to a conventional single-mode fiber (SMF).

We present a simple method to check the exact realization of a radially polarized light beam by means of a vortex-sensing diffraction grating. The use of this grating easily allows the determination of the topological charges included in each of the two circular polarization components of the incident beam. Therefore a pure radially polarized beam can be easily distinguished from a pseudo-radially polarized beam. Experimental results are presented with radial beams generated with two different devices: a patterned radial polarizer and a specially designed liquid crystal device.

New optical materials and processes for making novel materials is key to almost all scientific developments of optical systems and devices, including lasers, sensors, detectors, cameras, solar cells, and communication and space systems. For example, optical communication, which is the basis for internet, phone, and data systems, started with the advent of low-loss optical fibers in the early 1970s. Low-loss fibers became a reality because of the invention of a new vapor phase deposition process which enabled the manufacture of ultimate high-purity glass materials. The solar cell devices for much-needed energy harvesting also depend on new materials. Therefore, research in new materials, processes, characterization, and diagnostic techniques are always very important and essential.

We have applied principal component analysis to examine trial-to-trial variability of reflectances of automotive coatings that contain effect pigments. Reflectance databases were measured from different color batch productions using a multi-angle spectrophotometer. A method to classify the principal components was used based on the eigenvalue spectra. It was found that the eigenvalue spectra follow distinct power laws and depend on the detection angle. The scaling exponent provided an estimation of the correlation between reflectances and it was higher near specular reflection, suggesting a contribution from the deposition of effect pigments. Our findings indicate that principal component analysis can be a useful tool to classify different sources of spectral variability in color engineering.

Two sets of c-Si solar cells varying in front side phosphorus doped emitters were produced by standard screen printing techniques. The first group of samples, 3121, was prepared by a combination of standard washing and a bath with a highly dilute HF before diffusion of n⁺ -emitter. The second group of samples, 3122, was treated only with standard washing. A comparison of solar cell conversion efficiency and results from a noise spectroscopy, microplasma, and electroluminescence presence are presented. As was already shown in previous publications noise spectral density reflects the quality of solar cells, and thus represents an alternative advanced cell diagnostic tool. Our results confirm this relationship and moreover bring clear evidence for the maximum spectral noise voltage density being related to the emitter structure. The best results were reached for the group of solar cells in sample 3122, which was treated only with standard washing.

We present a method for the production of segmented optics. It is a process developed at INAF-Osservatorio Astronomico di Brera (INAF-OAB) employing commercial of-the-shelf materials. It is based on the shaping of thin glass foils by means of forced bending that occurs at room temperature [cold-shaping (CS)]. The glass is then assembled into a sandwich structure for retaining the imposed shape. The principal mechanical features of the mirrors are their low weight, rigidity and environmental robustness. The cost and production time also are competitive. We sum up the results achieved during research and development performed in the past years. We have investigated the theoretical limits of the structural components by means of parametric finite elements analyses; we also discuss the effects caused by the most common structural loads. Finally, the process implementation, the more significant validation tests and the mass production at the industry are described.

We present a new analytical study of metallic nanoparticles, working in the infrared and visible frequency range. The structure consists of triaxial ellipsoidal resonating inclusions embedded in a dielectric environment. Our aim is to develop a new analytical model for the ellipsoidal nanoparticles to describe their resonant behaviors and design structures that satisfy specific electromagnetic requirements. The obtained models are compared to the numerical values, performed by full-wave simulations, as well as to the experimental ones reported in literature. A good agreement among these results was obtained. The proposed formula is a useful tool to design such structures for sensing applications.

Microchannel plate (MCP) detectors are frequently used in space instrumentation for detecting a wide range of radiation and particles. The capability to detect non-thermal, low energy, neutral species is crucial for the Emitted Low-Energy Neutral Atoms (ELENA) sensor, which is part of the Search for Exospheric Refilling and Emitted Natural Abundances (SERENA) package on board the Mercury Planetary Orbiter (MPO) spacecraft of the BepiColombo mission of European Space Agency to Mercury, which is scheduled for launch in August 2015. ELENA is a time-of-flight sensor based on a novel concept using an ultrasonic oscillating shutter (start section) and MCP detector (stop detector). The ELENA scientific objective is to monitor the emission of neutral atoms from the surface of Mercury by detecting energetic neutral atoms in the range 10 eV to 5 keV, within 76 deg FOV, perpendicular to the S/C orbital plane. The surface is scanned due to the spacecraft motion. In particular, processes of particle release from the surface will be investigated by identifying particles released via solar wind-induced ion sputtering (with energies <1  eV to <100  eV ) as well as energetic hydrogen atoms, which are back-scattered solar wind protons, at energies of hundreds of eV. MCP absolute detection efficiency, for very low energy neutral atoms (E<30  eV ), is a crucial point for this investigation. At Messkammer für Flugzeitinstrumente und time-of-flight facility of the University of Bern, measurements on three MCP, with different coatings, have been performed providing the first data of MCP detection efficiencies in the energy range 10 eV to 1 keV.

Here, we provide an overview of broadband cosite interference reduction using an optical system to perform incoherent counter-phase modulation and subtraction. The equation governing interference cancellation depth is derived and discussed with respect to two key parameters, attenuation and delay accuracy. Cancellation depth is then examined with respect to signal bandwidth and device parameters to provide a context for predicted cancellation performance. Experimentally recorded interference cancellation data is presented along with predicted performance to show the agreement of theory and data.

A dual-band optics design for disjoint spectral bands and for a cooled FPA sensor, sensitive to both bands, is presented. The use of special optical splitting mechanisms enables matching the optical paths of both bands to the same sensor. Reasonable optical performance and good registration were achieved for dual bands such as 8 to 12 μm together with 3.6 to 4.2 μm, and for the 3.6 to 4.2 μm band with various monochromatic laser bands in the 1.06 to 1.8 μm spectral range. Regular IR materials were used with aspheric and diffractive surfaces. Both single-objective designs and zoomed-objective designs are presented.

A static broadband snapshot imaging spectrometer (BSIS) is proposed. This device consists of a telescope, four prisms, a focusing lens, and a detector. The first prism disperses sharply in the visible range along the vertical direction, and it is relatively nondispersive in the mid-wave infrared range. The second prism controls the beam deviation introduced by the first prism. The third prism is substantially more dispersive in the mid-wave infrared range than within the visible range along the horizontal direction. The fourth prism controls the beam deviation caused by the third prism. The BSIS will disperse the spectra of a target to form a V-shaped dispersion pattern (DP). The formulas and numerical simulation of the DP are given. The BSIS can locate multiple targets based only on one frame of data. The BSIS is suitable for detecting and measuring energetic targets in real time.

Ray tracing still is the workhorse in optical design and simulation. Its basic principle, propagating light as a set of mutually independent rays, implies a linear dependency of the computational effort and the number of rays involved in the problem. At the same time, the mutual independence of the light rays bears a huge potential for parallelization of the computational load. This potential has recently been recognized in the visualization community, where graphics processing unit (GPU)-accelerated ray tracing is used to render photorealistic images. However, precision requirements in optical simulation are substantially higher than in visualization, and therefore performance results known from visualization cannot be expected to transfer to optical simulation one-to-one. In this contribution, we present an open-source implementation of a GPU-accelerated ray tracer, based on nVidias acceleration engine OptiX, that traces in double precision and exploits the massively parallel architecture of modern graphics cards. We compare its performance to a CPU-based tracer that has been developed in parallel.

We fabricate two-dimensional photonic quasicrystal lattices in LiNbO₃ :Fe photorefractive crystal by a single amplitude mask with eight holes. We analyze the photonic quasicrystal structure by plane wave guiding, Brillouin-zone spectroscopy, and far-field diffraction pattern imaging. In addition, we design a more complex Penrose-tiled structure with 7-, 9-, 10-, 14-, and 16-fold rotational symmetry, along with a two-dimensional mixed photonic structure, which behaves just as if we embedded some defect sites into a hexagonal structure. This is a simple way of embedding defect sites into a photonic structure by designing the amplitude mask properly, and it can be applied in every laboratory.

We investigated the effects of various polishing additives added to cerium oxide slurry on the polishing properties of phosphate laser glass. The results showed that additives could change the polishing efficiency of the slurry and affect the surface quality of the laser glass. After polishing, the surface roughness of the glass increased and even micrometer-scale etch pits formed on the glass surface. The additive with 1.05% by weight LaF ₃ improved the polishing efficiency significantly while controlling the surface roughness of the laser glass. From the chemical-reactions perspective, a model was proposed to analyze the polishing mechanism based on the chemical composition and structure of the phosphate laser glass material and on current and previous experimental phenomena.

An algorithm for analyzing a vibrating target by a dominant harmonic order determination based on Fourier transform in a self-mixing system over wide optical feedback regimes (very weak, weak, and moderate regimes) is presented. The basic frequency of a self-mixing interference signal is used to determine the frequency of vibration, and the dominant harmonic order is proportional to the amplitude of vibration. The algorithm also allows calculation of the correct target movement at extremely low signal-to-noise ratios. The validity of the proposed algorithm was demonstrated by means of simulated signals and confirmed by several experimental measurements. The maximum error of the amplitude is about 0.16 μm and the maximum error of the frequency is about 2.5%. It can be used to demodulate the microscopic vibration of a remote target.

Copper is a heavy metal, which is used in heat and electrical conductors and in a multitude of alloys in the technical context. Moreover, it is a trace element that is essential for the life of organisms but can cause toxic effects in elevated concentrations. Maximum limits in water and beverages exist. Here, the decrease of the fluorescence lifetime of green fluorescent protein (GFP) by Förster resonance energy transfer is used to measure the copper ion concentration in drinking water. Therefore, a system is developed that is based on a GFP sample in a predefined concentration. The GFP mutant can be excited with blue light. For binding of copper ions, a His-tag is included in the GFP. After measuring the fluorescence lifetime of pure GFP, the copper determination of the sample is performed by lifetime measurement. Therefore, the lifetime can be assigned to the copper concentration of the GFP-doped drinking water sample. In summary, a method for the quantification of copper ions based on changes of the fluorescence lifetime of GFP is developed, and the measurement of the copper concentration in water samples is performed.

In this paper, we propose an aberration metrology (AM) of a lithographic projection lens based on aerial images (AI) by using a quadratic relationship model (Quad) between the aerial-image intensity distribution and the Zernike coefficients. The proposed method (AMAI-Quad) uses principal component analysis and multiple linear regression analyses for model generation. The quadratic model is, then, used to extract Zernike coefficients by a nonlinear least-squares minimizing technique. The best linear constrain condition is estimated by optimizing the illumination settings. Compared with earlier techniques, based on a linear relationship between Zernike coefficients and AIs, the new method can extend the orders of Zernike coefficients measured. The application of AMAI-Quad to AIs, computed by lithography simulators PROLITH and Dr.LiTHO, demonstrated an extension of measurement range to 90mλ and an enhancement of measurement accuracy by more than 30 percent.

The Space Surveillance Telescope (SST) is a three-mirror Mersenne-Schmidt telescope with a 3.5 m primary mirror. It is designed to rapidly scan for space objects, particularly along the geosynchronous belt, approximately 36,000 km above the Earth. The SST has an unusually short focal ratio of F/1.0 and employs a camera composed of curved charge-coupled devices to match the telescope’s inherent field curvature. The field-of-view of the system is 6 square degrees. While the unique system design is advantageous for space surveillance capabilities, it presents a challenge to alignment due to an inherently small depth of focus and the additional degrees of freedom introduced with a powered tertiary mirror. The alignment procedure developed for the SST at zenith pointing is discussed, as well as the maintenance of focus and alignment of the system across a range of elevation and temperature conditions. Quantitative performance metrics demonstrate the success of the system alignment during the telescope’s first year of operation.

The gamma nonlinearity of the digital projector leads to obvious phase errors in the phase measuring profilometry. Based on the Fourier spectrum analysis of the captured pattern, a robust gamma correction method is proposed in this paper. An orthogonal sinusoidal grating precoded with two different known gamma values is used to evaluate the gamma value of the pattern. The evaluated gamma value is then encoded into the computer-generated phase-shifting fringe patterns before the fringe patterns are sent to the digital projector, which makes the captured fringe patterns well-sinusoidal and alleviates the phase errors caused by the gamma nonlinearity. Compared with other gamma correction methods, only one captured pattern is needed to evaluate the gamma value without loss of the accuracy. With the proposed method, a fast and accurate three-dimensional shape measurement can be achieved using the conventional three-step phase-shifting algorithm. Experiments have verified its feasibility and validity.

We present the validation for Ronchigram recovery with the random aberrations coefficients (ReRRCA) algorithm. This algorithm was proposed to obtain the wavefront aberrations of synthetic Ronchigrams, using only one Ronchigram without the need for polynomial fits or trapezoidal integrations. The validation is performed by simulating different types of Ronchigrams for on-axis and off-axis surfaces. In order to validate the proposed analysis, the polynomial aberration coefficients that were used to generate the simulated Ronchigrams were retrieved. Therefore, it was verified that the coefficients correspond to the retrieved ones by the algorithm. The results show that the ReRRCA algorithm retrieves the aberration coefficients from the analyzed Ronchigram with a maximum error of 9%.

X-ray photoelectron spectroscopy (XPS) is used to compare the composition as a function of depth of as-grown zinc oxide (ZnO) films heavily doped with Ga and similar samples annealed in air for 10 min at 600°C, with particular attention given to the near-surface region. Films are grown by pulsed laser deposition (PLD) using a ZnO target containing 3 wt% Ga ₂ O ₃ . Electrical properties of these samples are determined from temperature-dependent Hall-effect measurements. The as-grown film has the following characteristics: (1) ∼1∶1 Zn:O ratio with a Ga concentration of ∼3.3 at %; (2) no excess Ga in the near-surface region; and (3) excellent electrical characteristics: ρ=2.42×10 ⁻⁴   Ω-cm , n=8.05×10 ²⁰   cm −3 , and μ=32.1   cm ² /V-s -s at 300 K. For the annealed sample: (1) the Zn:O ratio remains ∼1∶1 , but the Ga concentration is ∼3 at %, which is ∼10% lower than in the as-grown film; (2) ∼7 at % Ga is measured in the near-surface region; and (3) a significant increase in resistivity to ρ[/i]=0.99  Ω-cm , n=1.97×10 ¹⁸   cm ⁻³ , and μ=3.2  cm ² /V-s at 300 K. Analysis of the O chemical shift suggests formation of a mixed ZnO/Ga ₂ O ₃ surface layer ≤5-nm -thick accounts for the observed changes in the Ga profile after annealing.