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For nowadays the main goal for using the sensors are the investigations the new gas sensitive materials. Optical gas sensors are characterized by most of the high response. Such sensors distinguished by the high sensitivity, selectivity and stability and have long-term operation 1 . The principle of operation is based on the absorption of NH 3 gas by sensitive element of primary transducer and changing the spectral characteristics. Principle of gas sensor operation is based on the registration of shift of the wavelength minimum in spectral characteristics of cholesteric-nematic mixture (CNM). In paper as sensitive material used the CNM on the basis of BLO-61 cholesteric liquid crystal (CLC) with 5CB nematic liquid crystal (NLC) doped by single and multiwall carbon nanotubes. The optimal nanocomposite structure composition to obtain the maximum value of spectral sensitivity coefficient was determined. In paper was found the increasing the nanotubes concentration in CNM leads to increasing the spectral sensitivity coefficient independently of 5CB concentration in CNM, but the maximum nanotubes concentration was chosen to take in to account the optical transparency of experimental samples. Gas sensitive material on the basis of cholesteric-nematic mixture doped carbon nanotubes for optoelectronic NH 3 gas sensor.

The phenomenon of laser light scattering provides the technology for visualization and testing the inner structure and homogeneity of materials. Some of them excited by the laser light in the tomographic process can emit light the wavelength of which is different than that of excitation laser. Such photoluminescence can be a source of additional information of the material’s structure. Combining the Laser Scattering Tomography (LST) and Spectrometry techniques has enabled us to develop a new type of an LST technique. The system is useful for investigations of various materials like semiconductors (Si, GaAs) ceramics, crystals for passive absorbers for high power pulse lasers, and laser crystals.

The paper presents a relatively simple though effective approach to fringe field processing for variable wavelengthinterferometry- related techniques including a detailed analysis of noise influence on the accuracy of fringe parameters extraction.

In this paper, influence of the standard single mode fibre (SSMF) dispersion characteristic on the multi-wavelength 1310 nm wavelength domain 400 and 1000 Gbit/s transmission is investigated. The four-wave mixing (FWM) effect and residual chromatic dispersion can significantly limit the system performance. Limitations due to the FWM effect are studied for various types of SSMF fibre. Suppression of the FWM effect will require the channel spacing of at least 1.4 nm. The FWM effect can be suppressed in fibres with the large core area, allowing much higher input powers or narrower channel spacing. Further limitations due to the residual chromatic dispersion are evaluated and the capacity and transmission trade-off’s are studies in detail. It is shown that, the chromatic dispersion related limitations are pronounced for the wavelength channel allocation that is favorable from the manufacturing and installation point of view. These limitations can be omitted by the alignment of the wavelength channels to the zero-dispersion wavelength band and its management in the fibre infrastructure. The line rate of 40 Gbit/s outperforms the 50 Gbit/s taking into account the transmission capacity and distance. The presented results support development of 400 Gbit/s and 1000 Gbit/s Ethernet physical layer.

In this paper a new concept of human breath detection by means of fiber Bragg grating (FBG) based temperature sensor is reported. In presented approach, temperature of exhaled air is directly measured by FBG, and its Bragg wavelength changes allow for determine breathing rate. Experimental results of comparison the FBG sensor with electronic one, show significant advantages of our solution, especially when faster and/or plate breathing is detected. Another advantage of proposed fiber Bragg grating based breathing rate sensor is its ability to work in the high electromagnetic field environment, for example during the magnetic resonance imaging.

The miniaturization technology of the FPD panel have been advanced continuously, and it is said that the reducing rate is about 0.7 times for three years. Therefore, an exposure equipment of the 1.5 μm resolution was released from manufacturers in 2016. As one of some methods to realize 1.5 μm resolution, change from the broadband light to i-line single wavelength light has been selected. However, it is known that CD uniformity is become large, when a conventional pellicle is used in i-line single wavelength exposure[1]. Therefore, it is needed products suitable for i-line single wavelength exposure. In this paper, influence of the pellicle is investigated between conventional pellicle and i-line pellicle. Keywords：FPD, pellicle, i-line, resolution, CD uniformity.

Plasmonic optical trapping allows trapping and manipulation of micro- and even nanometer-sized particles using localized and enhanced electric fields by plasmon resonance in metallic nanostructure. We consider an optical conveyor belt consisting of an array of nanodisks acting as optical tweezers with different sizes to implement a system to trap and manipulate particles through a laser-induced gradient force. An electric field induced and localized at each optical resonator is sensitive to the wavelength and polarization. The maximum electric field is enhanced at resonant wavelength depending on the shape and size of the plasmonic nanostructure used for light localization. By changing the light wavelength and polarization, the position of localized light induced in the disk can be determined and nanoparticles can be moved to a desired location through the variation of resonance conditions without any mechanical forces.

Optical diagnostics techniques are becoming important for technical art history (TAH) as well as for heritage conservation. In recent years, optical coherence tomography (OCT) has been increasingly used as a novel technique for the inspection of artwork, revealing the stratigraphy of paintings. It has also shown to be an effective tool for vanish layer inspection. OCT is a contactless and non-destructive technique for microstructural imaging of turbid media, originally developed for medical applications. However current OCT instruments have difficulty in paint layer inspection due to the opacity of most pigments. This paper explores the potential of OCT for the investigation of paintings with coloured grounds. Depth scans were processed to determine the light penetration depth at the optical wavelength based on a 1/e light attenuation calculation. The variation in paint opacity was mapped based on the microstructural images and 3D penetration depth profiles was calculated and related back to the construction of the artwork. By determining the light penetration depth over a range of wavelengths the 3D depth perception of a painting with coloured grounds can be characterized optically.

Holographic techniques have been used to measure the shape and the radial deformation of a blood vessel model and a real sheep aorta. Measurements are obtained from several holograms recorded for different object states. For each object state, two holograms with two different wavelengths are multiplexed in the same digital recording. Thus both holograms are simultaneously recorded but the information from each of them is separately obtained. The shape analysis gives a wrapped phase map whose fringes are related to a synthetic wavelength. After a filtering and unwrapping process, the 3D shape can be obtained. The shape data for each line are fitted to a circumference in order to determine the local vessel radius and center. The deformation analysis also results in a wrapped phase map, but the fringes are related to the laser wavelength used in the corresponding hologram. After the filtering and unwrapping process, a 2D map of the deformation in an out-of-plane direction is reconstructed. The radial deformation is then calculated by using the shape information.

The sizes of non-negligible defects in the patterning of a semiconductor device continue to decrease as the dimensions for these devices are reduced. These “killer defects” disrupt the performance of the device and must be adequately controlled during manufacturing, and new solutions are required to improve optics-based defect inspection. To this end, our group has reported [Barnes et al., Proc. SPIE 1014516 (2017)] our initial five-wavelength simulation study, evaluating the extensibility of defect inspection by reducing the inspection wavelength from a deep-ultraviolet wavelength to wavelengths in the vacuum ultraviolet and the extreme ultraviolet. In that study, a 47 nm wavelength yielded enhancements in the signal to noise (SNR) by a factor of five compared to longer wavelengths and in the differential intensities by as much as three orders-of-magnitude compared to 13 nm. This paper briefly reviews these recent findings and investigates the possible sources for these disparities between results at 13 nm and 47 nm wavelengths. Our in-house finite-difference time-domain code (FDTD) is tested in both two and three dimensions to determine how computational conditions contributed to the results. A modified geometry and materials stack is presented that offers a second viewpoint of defect detectability as functions of wavelength, polarization, and defect type. Reapplication of the initial SNR-based defect metric again yields no detection of a defect at λ = 13 nm, but additional image preprocessing now enables the computation of the SNR for λ = 13 nm simulated images and has led to a revised defect metric that allows comparisons at all five wavelengths.

The objective of this study is to propose and introduce nonlinear modal propagation analysis (NMPA) method being a viable way to study the application of graphene based multimode interference (MMI) coupler as an optical refractive index sensor. The purpose of using graphene in this study is because of its high optical nonlinearity as well as having a small bandgap due to its thin layer. The graphene based sensor can be tuned for highest sensitivity in wavelength and refractive index to detect the clad material. Graphene will act as the core of the sensor which will be placed on top of the sample. The clad refractive index value can be obtained by observing and analyzing the change in the output facet intensity of the sensor. The result also shows that the sensor has high sensitivity due to the usage of graphene and nonlinear region.

We propose a novel 8-channel wavelength multimode interference (MMI) demultiplexer in slot waveguide structures that operated at 1530 nm, 1535 nm, 1540 nm, 1545 nm, 1550 nm, 1555 nm, 1560 nm and 1565 nm wavelengths. Gallium nitride (GaN) surrounded by silicon (Si) was founded as suitable materials for the slot-waveguide structures. The proposed device was designed by seven 1x2 MMI couplers, fourteen S-band and one input taper. Numerical investigations were carried out on the geometrical parameters by using a full vectorial-beam propagation method (FVBPM). Simulation results show that the proposed device can transmit 8-channel that works in the whole C-band (1530- 1565 nm) with low crosstalk ((-19.97)-(-13.77) dB) and bandwidth (1.8-3.6 nm). Thus, the device can be very useful in optical networking systems that work on dense wavelength division multiplexing (DWDM) technology.

The European XFEL is a large-scale user facility under construction in Hamburg, Germany. It will provide a transversally fully coherent X-ray radiation with outstanding characteristics: high repetition rate (up to 2700 pulses with a 0.6 milliseconds long pulse train at 10Hz), short wavelength (down to 0.05 nm), short pulses (in the femtoseconds scale) and high average brilliance (1.6x1025 photons / s / mm2 / mrad2/ 0.1% bandwidth)1. Due to the short wavelength and high pulse energies, mirrors need to have a high-quality surface, have to be very long (1 m), and at the same time an effective cooling system has to be implemented. Matching these tight specifications and assessing them with high precision optical measurements is very challenging. The mirrors go through a complicated and long process, starting from classical polishing to deterministic polishing, ending with a special coating and a final metrology assessment inside their mechanical mounts just before the installation. The installation itself is also difficult for such big mirrors and needs special care. In this contribution we will explain how we implemented the installation process, how we used the metrology information to optimize the installation procedure and we will show some preliminary results with the first mirrors installed in the European XFEL beam transport.

The goal of this work is to describe a simulatively designed scatterometry approach for the in-line characterization of sub-wavelength sinusoidal gratings, which are formed on a transparent foil in a roll-to-roll procedure. The challenge is to acquire the 3D information of the workpiece, i.e., to measure the grating height in addition to the grating period with nm precision. The grating period is obtained straightforward from the position of the first order diffraction maxima in the reflection and the transmission region. For determining the grating height, the inverse problem is solved, i.e., the relation between the scattered intensities of the diffraction maxima and the grating height is extracted from light scattering simulations. The measurement uncertainty is evaluated for different instrumentation and simulation parameters, such as the detection and incidence angle, the laser wavelength as well as the input parameters of the simulation. As a result, the measurement uncertainty for the grating period and the height is estimated to 0.3 nm and ≤8 nm, respectively, when using laser light in the visible wavelength range. Large area scanning measurements performed offline using the setup parameters derived from simulations verify the sensitivity of the presented measurement approach for identifying local variations of the spatial surface properties. Depending on the chosen detection system, sampling rates up to the MHz range are feasible meeting the requirements of in-line process control of the roll-to-roll production procedure.

Controlling the polarization of light is crucial in numerous applications such as spectroscopy, ellipsometry, photo lithography or industrial vision. Polarization control can be realized by wire grid polarizers (WGPs), which are large aspect ratio, zero order gratings. These elements provide an anisotropic transmittance depending on the polarization direction of the incident light. WGPs’ high attractiveness originates from their large free aperture, while simultaneously being extremely thin. Furthermore, these elements can be easily integrated into other nano-optical devices. Recently, such elements were successfully developed for applications down to the deep ultra violet spectral range. However, at shorter wavelengths the influence of roughness of the structures poses a severe limitation on the feasible optical performance. To tackle this problem, we numerically simulated the impact of line edge roughness on the polarization properties of WPGs. Therefore, we generated edge position data of rough grating lines by means of the Thorsos method and calculated the resulting optical response by finite difference time domain method. With this procedure the influence of standard deviation, correlation length, Hurst exponents and wavelength was investigated. We find that for standard deviations of 2.5 nm and 5.0 nm the polarization contrast is reduced by a factor of 3 and 7, respectively. The polarization contrast shows a minimum for intermediate correlation lengths, while virtually no impact of the Hurst exponent is observed. This is explained by several mechanisms occurring for different ratios between the spatial frequency of the roughness and the frequency of incident light. Our theoretical findings correlate well with experimental results we retrieved with measured roughness parameters of fabricated elements.

The article of record as published may be found at http://dx.doi.org/10.1117/12.2264952 Conventional directional sound sensing systems employ an array of spatially separated microphones to achieve directivity. However, there are insects such as the Ormia ochracea fly that can determine the direction of sound using a miniature hearing organ much smaller than the wavelength of sound it detects. The fly’s eardrums are coupled mechanically with a separation of only 0.5 mm and yet have a remarkable sensitivity to the direction of sound. The MEMS based sensor mimicking the fly’s hearing system was fabricated using an SOI substrate with a 25 μm device layer. The sensor consists of two 1.5 mm x1.6 mm wings connected in the middle by a 2.7 mm x 30 μm bridge. The entire structure is connected to the substrate by two torsional legs at the center. The frequency response of the sensor showed two resonance frequencies at approximately 1.1 kHz (rocking) and 1.5 kHz (bending). The resonance at 1.1 kHz is due to rocking of the wings by twisting the legs and the other at 1.5 kHz is due to bending of the bridge. The response of the sensor was probed electronically using comb finger capacitors integrated to the edges of the wings and with the help of an MS3110 chip. A peak output voltage of about 9V/Pa was measured for sound incident normal to the device at the resonance frequency of the bending mode. The bearing of the incident sound under these conditions could be determined to within a few degrees. These findings indicate the potential use of the MEMS sensor to locate sound sources with high accuracy. CRUSER NRP ONR

In this work, an aluminium nitride based piezoelectric resonator (05-mode) was fabricated and characterized to study how various factors, such as pressure, gas composition, the resonator geometry or the order of the vibrational mode, influence the resonant frequency and quality factor of micro resonators. In order to determine the resonant parameters of interest, an interface circuit was implemented and included within a closed-loop scheme. The effect of viscosity and density of the gases under test on the resonant parameters can be determined through a calibration process using different gases, an impedance analyser and theoretical values of density and viscosity reported in the literature. Depending on gas species different gas damping effects in the molecular, transitional and viscous flow regimes were observed. However, as the resonant mode number increases and therefore the resonant frequency, the acoustic wavelength reduces, the contribution of acoustic effects on the energy loss cannot be neglected any more in comparison with viscous effects. Our results demonstrate the performance of the resonator in different gases (Air, N2, Ar, CO2 and He) and pressures (0.1-950 mbar) by developing and applying specific experimental setup.

Our intention is to develop high-resolution stigmatic spectral imaging in the XUV (2 – 40 nm). We have designed, aligned and tested a broadband stigmatic spectrometer for a range of 12–30 nm, which makes combined use of a normalincidence multilayer mirror (MM) (in particular, a broadband aperiodic MM) and a grazing-incidence plane varied linespace (VLS) reflection grating. The concave MM produces a slightly astigmatic image of the radiation source (for instance, the entrance slit), and the VLS grating produces a set of its dispersed stigmatic spectral images. The multilayer structure determines the spectral width of the operating range, which may amount to more than an octave in wavelength (e.g. 12.5–30 nm for an aperiodic Mo/Si MM), while the VLS grating controls the spectral focal curve. The stigmatism condition is satisfied simultaneously for two wavelengths, 14 and 27 nm. In this case, the condition of non-rigorous stigmatism is fulfilled for the entire wavelength range. A LiF laser plasma spectrum was recorded in one 0.5 J laser shot. A spatial resolution of 26 μm and a spectral resolution of 900 were demonstrated in the 12.5 – 25 nm range. We also report the design of a set of flat-field spectrometers of Harada type with VLS gratings. VLS gratings were made by ebeam and interference lithography. A technique (analytical + numerical) was developed for calculating optical schemes for writing plane and concave VLS gratings with predefined line density variation.

We present a laboratory high-aperture monochromator-reflectometer employing laser-plasma radiation source and three replaceable Schwarzschild objectives for a certain range of applications in the soft X-ray spectral waveband. Three sets of X-ray multilayer mirrors for the Schwarzschild objectives enable operation of the reflectometer at the wavelengths of 135, 171 and 304 A, while a goniometer with three degrees of freedom allows different measurement modes. We have used the facility for a laboratory CCD calibration at the wavelengths specified. Combined with the results of the CCD sensitivity measurements conducted in the VUV spectral waveband, the total outcome provides a more comprehensive understanding of the CCD effectivity in a wide spectral range.

The infrared wire-grid polarizer consisting of an Al grating, Si, and sol-gel derived zirconia grating film was fabricated by soft imprint process and Al shadow coating processes. A silicone mold was used because of its low surface energy, flexibility, and capability of transferring submicrosized patterns. As a result, the Al grating with a pitch of 400 nm and a depth of 100 nm was obtained on the zirconia grating film. The fabricated polarizer exhibited a polarization function with the TM transmittance greater than that of the Si substrate in the specific wavelength range of 3.6–8.5 μm, because the zirconia film acted as an antireflection film. The maximum value was 63% at a wavelength of 5.2 μm. This increment of the TM transmission spectrum results in interference within the zirconia film. Also, the extinction ratio exceeded almost 20 dB in the 3-8.8 μm wavelength range.

We evaluate a recently devised design of vertical-cavity enhanced resonant thermal emitter (VERTE) regarding stability to fabrication tolerances of PVD layer deposition techniques. Such an emitter achieves narrowband and coherent thermal emission and is composed of an multilayer stack of dielectric layers (silicon and silica) on top of a reflective metal (silver) structure. The silica layer above the metal acts as a vertical cavity enhancing the electromagnetic field between the reflective metal and the dielectric stack forming a Bragg mirror (1-D photonic crystal). In our previous work, we identified several suitable five-layer-stack configurations, which considered several features and limitations of a real-world device, such as temperature dependence of the materials, fabrication constraints or unwanted emission modes. However, the emission characteristics are very sensitive to the geometrical and optical properties of the material. In order to examine this behaviour, a Monte-Carlo algorithm was used to apply a Gauss-distributed error in depth (relative the unperturbed layer thickness) for every individual layer. The robustness of the emission properties against fabrication errors were evaluated and analyzed by significant statistical quantities. As expected, the main issue compromising the emission properties is a deviation of the resonance wavelength in relation to the initial target resonance wavelength of the unperturbed configuration. Interestingly, configurations with larger average layer thicknesses and therefore with larger absolute thickness deviations did not exhibit a larger variance of the emission wavelength. Instead, the variance slightly decreased or remained constant. A similar result was obtained for increasing the number of dielectric layers. In contrast, the peak emissivity (at normal incidence) was significantly influenced by the average layer depth of a configuration. Also, the effect of broadening of the spectral emittance curve due to random thickness fluctuations was evaluated. It was found that the broadening due to relative thickness errors can be considered as negligible for most configurations.

We propose the novel structure of an interferometric biosensor based on multimode interference (MMI) waveguides. We present the design of the biosensor using eigenmode expansion (EME) method in accordance with the requirements and standards of today's photonic technology. The MMI structures with a 90 nm Si3N4 core are used as power splitters with 5 outputs. The 5 high-resolution images at the end of the multimode region show high power balance. We analyze the coupling efficiency of the laser source with the structure, the excess loss and power imbalance for different compact MMI waveguides with widths ranging from 45 μm to 15 μm. For a laser source with a tolerance of ±1mm in linearization we could achieve a coupling efficiency of 52%. MMI waveguides with tapered channels show excess loss values under 0.5 dB and power imbalance values under 0.08 dB. In addition, we show that for a 10 nm deviation of the source wavelength from its optimal value and for a 10 μm deviation of the MMI length from its optimal value, the performance of the MMI waveguides remains acceptable. Finally, we analyze the power budget of the whole biosensor structure and show that it is sufficient for the proper operation of this device.

This effort develops and tests algorithms and a user-portable optical system designed to autonomously optimize the laser communication wavelength in open and coastal oceans. In situ optical meteorology and oceanography (METOC) data gathered and analyzed as part of the auto-selection process can be stored and forwarded. The system performs closedloop optimization of three visible-band lasers within one minute by probing the water column via passive retroreflector and polarization optics, selecting the ideal wavelength, and enabling high-speed communication. Backscattered and stray light is selectively blocked by employing polarizers and wave plates, thus increasing the signal-to-noise ratio. As an advancement in instrumentation, we present autonomy software and portable hardware, and demonstrate this new system in two environments: ocean bay seawater and outdoor test pool freshwater. The next generation design is also presented. Once fully miniaturized, the optical payload and software will be ready for deployment on manned and unmanned platforms such as buoys and vehicles. Gathering timely and accurate ocean sensing data in situ will dramatically increase the knowledge base and capabilities for environmental sensing, defense, and industrial applications. Furthermore, communicating on the optimal channel increases transfer rates, propagation range, and mission length, all while reducing power consumption in undersea platforms.

Silicon oxycarbide (SiOC) thin films are produced with reactive rf magnetron sputtering of a silicon carbide (SiC) target on Si (100) and SiO2/Si substrates under varying deposition conditions. The optical properties of the deposited SiOC thin films are characterized with spectroscopic ellispometry at multiple angles of incidence over a wavelength range 300- 1600 nm. The derived optical constants of the SiOC films are modeled with Tauc-Lorentz model. The refractive index n of the SiOC films range from 1.45 to 1.85 @ 1550 nm and the extinction coefficient k is estimated to be less than 10-4 in the near-infrared region above 1000 nm. The topography of SiOC films is studied with SEM and AFM giving rms roughness of 0.9 nm. Channel waveguides with a SiOC core with a refractive index of 1.7 have been fabricated to demonstrate the potential of sputtered SiOC for integrated photonics applications. Propagation loss as low as 0.39 ± 0.05 dB/mm for TE and 0.41 ± 0.05 dB/mm for TM polarizations at telecommunication wavelength 1550 nm is demonstrated.

In this work we correlate the dimension of the waveguide with small variations of the refractive index of the material used for the waveguide core. We calculate the effective modal refractive index for different dimensions of the waveguide and with slightly variation of the refractive index of the core material. These results are used as an input for a set of Finite Difference Time Domain simulation, directed to study the characteristics of amorphous silicon waveguides embedded in a SiO 2 cladding. The study considers simple linear waveguides with rectangular section for studying the modal attenuation expected at different wavelengths. Transmission efficiency is determined analyzing the decay of the light power along the waveguides. As far as near infrared wavelengths are considered, a-Si:H shows a behavior highly dependent on the light wavelength and its extinction coefficient rapidly increases as operating frequency goes into visible spectrum range. The simulation results show that amorphous silicon can be considered a good candidate for waveguide material core whenever the waveguide length is as short as a few centimeters. The maximum transmission length is highly affected by the a-Si:H defect density, the mid-gap density of states and by the waveguide section area. The simulation results address a minimum requirement of 300nm×400nm waveguide section in order to keep attenuation below 1 dB cm -1 .

Integrated optics has the potential to play a transformative role in astronomical instrumentation. It has already made a significant impact in the field of optical interferometry, through the use of planar waveguide arrays for beam combination and phase-shifting. Additionally, the potential benefits of micro-spectrographs based on array waveguide gratings have also been demonstrated. Here we examine a new application of integrated optics, using ring resonators as notch filters to remove the signal from atmospheric OH emission lines from astronomical spectra. We also briefly discuss their use as frequency combs for wavelength calibration and as drop filters for Doppler planet searches. We discuss the theoretical requirements for ring resonators for OH suppression. We find that small radius (< 10 μm), high index contrast (Si or Si3N4) rings are necessary to provide an adequate free spectral range. The suppression depth, resolving power, and throughput for efficient OH suppression can be realised with critically coupled rings with high self-coupling coefficients. We report on preliminary laboratory tests of our Si and Si3N4 rings and give details of their fabrication. We demonstrate high self-coupling coefficients (> 0:9) and good control over the free spectral range and wavelength separation of multi-ring devices. Current devices have Q ≈ 4000 and ≈ 10 dB suppression, which should be improved through further optimisation of the coupling coefficients. The overall prospects for the use of ring resonators in astronomical instruments is promising, provided efficient fibre-chip coupling can be achieved.

The authors focused on the problems of measurement of attenuation and homogeneity of special fibers of polydimethylsiloxane (PDMS) depending on three different procedures for mixing PDMS and curing agent. We used a two-component elastomer Sylgard 184. For mixing was used a defined ratio of 10:1 for PDMS, which was determined based on the datasheet. Curing of samples took place in a heat box at a constant temperature of 80 °C ± 3 °C. Three procedures were defined for mixing PDMS and curing agent: manual, using a laboratory shaker and ultrasonic baths. For each method of mixing was carried out a total of 25 samples. The test samples have a defined shape in the form of a cylindrical waveguide with a diameter of 5 mm and a length of 50 mm. The whole process of production of cylindrical waveguides applied in the protective vacuum box. To verify the homogeneity of the samples were divided into 5 mm sections, measured was the attenuation constant in both directions. As a source of radiation was used LED (Light Emitting Diode) with a wavelength of 470 nm. The outcome of this study is the evaluation of the quality waveguides by the size of the total attenuation and the attenuation constant for analysis of spreading out in homogeneities depending on the procedure of mixing PDMS and curing agent. The analysis performed with regarding the use of PDMS for its optical properties.

The results of formation conditions studies of a highly directional supercontinuum (SC) in a visible spectrum range obtained upon aberration spherical-mirror focusing of a radiation pulse with a wavelength of 940 nm, duration of 70 fs, and energy of 8–15 mJ are presented. It is shown that after visible filament there are two directed white light beams diverging relative to each other at an angle of 1.4 0 . Formation every light beam occurs through a gradual conversion of the spectral composition from long wavelength to short wavelength (to 350 nm) in a spatially stable structure similar to a soliton with a transverse dimension ≤ 300 μm. The nature of the appearance these beams is due to formation of two zones with higher intensity before meridional plate owing to the distortion of the wavefront of the laser beam in conditions of the astigmatism and the Kerr effect. In result two minima in the phase distribution located outside the beam axis are realized, which lead to the appearance of two off-axis areas with higher radiation intensity and as a consequence of this the formation of two highly directional laser beams.

High average power wavelength tunable picosecond mid-IR source based on parametric down-conversion is being developed. The conversion system is pumped by a Yb:YAG thin-disk laser delivering 100 W of average power at 100 kHz repetition rate, 1030 nm wavelength, and 3 ps pulse width. First, part of the beam pumps an optical parametric generator (OPG) consisting of a PPLN crystal. The generated wavelength is determined by PPLN’s poling period and temperature. Signal beam covered wavelength range between 1.46 mμ and 1.95 mμ. The corresponding idler wavelengths are 3.5 mμ and 2.18 mμ, respectively. Signal beam of about 20 mW was generated at 2 W pumping and double pass arrangement of the OPG stage. The signal pulse energy is further boosted in an optical parametric amplifier (OPA) consisting of two KTP crystals. The signal beam was amplified to 2 W at pumping of 38 W. The idler beam is taken out of the OPA stage as well. Wavelength tuning by KTP crystals’ phase-matching angle change was achieved in ranges and 1.7 - 1.95 μm and 2.18 - 2.62 mμ for signal and idler beam, respectively.

Lasers based on stimulated-Raman-scattering process can be used for the frequency-conversion to the wavelengths that are not readily available from solid-state lasers. Parametric Raman lasers allow generation of not only Stokes, but also anti-Stokes components. However, practically all the known crystalline parametric Raman anti-Stokes lasers have very low conversion efficiencies of about 1 % at theoretically predicted values of up to 40 % because of relatively narrow angular tolerance of phase matching in comparison with angular divergence of the interacting beams. In our investigation, to widen the angular tolerance of four-wave mixing and to obtain high conversion efficiency into the antiStokes wave we propose and study a new scheme of the parametric Raman anti-Stokes laser at 503 nm with phasematched collinear beam interaction of orthogonally polarized Raman components in calcite under 532 nm 20 ps laser pumping. We use only one 532-nm laser source to pump the Raman-active calcite crystal oriented at the phase matched angle for orthogonally polarized Raman components four-wave mixing. Additionally, we split the 532-nm laser radiation into the orthogonally polarized components entering to the Raman-active calcite crystal at the certain incidence angles to fulfill the tangential phase matching compensating walk-off of extraordinary waves for collinear beam interaction in the crystal with the widest angular tolerance of four-wave mixing. For the first time the highest 503-nm anti-Stokes conversion efficiency of 30 % close to the theoretical limit of about 40 % at overall optical efficiency of the parametric Raman anti-Stokes generation of up to 3.5 % in calcite is obtained due to realization of tangential phase matching insensitive to the angular mismatch.

In the present work, on-chip dielectric diffraction gratings for steering the propagation of surface plasmon polaritons (SPP) are theoretically, numerically and experimentally studied. The investigated plasmonic gratings consist of dielectric ridges located on the SPP propagation surface (on the metal surface). In contrast to Bragg gratings, at normal incidence the periodicity direction of the grating is perpendicular to the SPP propagation direction. The studied gratings are designed using a simple plane-wave grating model and rigorously simulated using the aperiodic Fourier modal method for numerical solution of Maxwell’s equations. In particular, plasmonic grating-based beam splitter with subwavelength footprint in the propagation direction is presented. Along with the theoretical and numerical results, proof-of-concept experimental results are presented. The investigated grating-based plasmonic gratings were fabricated from resist on a silver film using electron beam lithography and characterized using the leakage radiation microscopy technique. The obtained experimental results are in good agreement with the performed numerical simulations. The proposed on-chip gratings may find application in the design of systems for optical information transmission and processing at the nanoscale.

Silver halide sensitized gelatin (SHSG) processes are interesting because they combine the spectral and energetic sensitivity of a photographic emulsions with good optical quality and high diffraction efficiency of dichromate gelatin (DCG). Previous papers had been demonstrated that it is possible to obtain diffraction efficiencies near to 90% with Agfa- Gevaert plates and Colour Holographic plates in SHSG transmission gratings. In this communication, we report on the performances measured at room temperature and in cryogenic conditions of a set of volume phase holographic gratings(VPHGs) manufactured with SHSG process aimed at their use in astronomical instrumentations. Two set of diffraction gratings has been manufactured using different processing. The first with SHSG process and the second with typical bleached process (developed with AAC and bleached in R-10). In both cases the plate was BB640, ultrafine grain emulsions with a nominal thickness of 9 μm. The recording was performed with asymmetric geometry a 30° degrees between the light beams of wavelength 632.8 nm (He-Ne laser), which give a raise a spectral frequency of 800 l/m. The exposure was between 46 to 2048 μJ/cm2. The results give us information about Bragg plane modification and reduction of diffraction efficiency when we introduced the VPHG to 77° K. In the case of SHSG process the final diffraction efficiency after cryogenic temperature are better at some exposure energy than previous measurements at room temperature. This experimental result give us possibilities to applied SHSG process in Astrophysics applications.

Ferroelectric liquid crystal blends containing a photoconductive chiral dopant and an electron trap reagent exhibit a large photorefractivity and fast response. They can be utilized in dynamic amplification of moving optical signals. In the present study, the enhancement of working wavelength to a longer wavelength regions was investigated. A series of photoconductive chiral dopants was prepared and the photorefractive properties were examined.

In this paper, we investigated laser performance of Er:Y2O3 ceramics at room temperature. With pulsed pumping with duty cycle of 1%, 1.02 W of peak output power was obtained at wavelength of 2.7 μm with slope efficiency of 3%. Furthermore, absorption spectra of the ceramics and temperature evolution for different pumping conditions were examined.

True colour Denisyuk-type hologram recording of diffusing objects in Bayfol® HX 102 self-developing photopolymer has been studied. In a first stage, monochromatic Denisyuk holograms of a standard white diffuser (Spectralon) have been recorded using lasers with wavelengths 442, 532 and 633 nm to determine the optimum exposure that gives maximum efficiency. The recording of holograms from a diffusing object has the particularity that intermodulation noise due to interference between waves arriving from different object points reduces effective index modulation. A maximum effective efficiency of 80% has been reached for monochromatic recording. In a second stage, a set of experiments has been carried out to determine the adequate relation of exposure for the recording of a Denisyuk hologram of the standard white diffuser with the three lasers simultaneously to get the maximum efficiency for each wavelength. With the determined optimal exposure, a hologram of a polychromatic diffusing object has been recorded, obtaining a good visual coincidence between hologram and original object.

Coded aperture correlation holography (COACH) is a recently developed incoherent digital holographic technique. In COACH, two holograms are recorded: the object hologram for the object under study and another hologram for a point object called PSF hologram. The holograms are recorded by interfering two beams, both diffracted from the same object point, but only one of them passes through a random-like coded phase mask (CPM). The same CPM is used for recording the object as well as the PSF holograms. The image is reconstructed by correlating the object hologram with a processed version of the PSF hologram. The COACH holographic technique exhibits the same transverse and axial resolution of the regular imaging, but with the unique capability of storing 3D information. The basic COACH configuration consists of a single spatial light modulator (SLM) used for displaying the CPM. In this study, the basic COACH configuration has been advanced by employing two spatial light modulators (SLMs) in the setup. The refractive lens used in the basic COACH setup for collecting and collimating the light diffracted by the object is replaced by an SLM on which an equivalent diffractive lens is displayed. Unlike a refractive lens, the diffractive lens displayed on the first SLM focuses light with different wavelengths to different axial planes, which are separated by distances larger than the axial correlation lengths of the CPM for any visible wavelength. This characteristic extends the boundaries of COACH from three-dimensional to four-dimensional imaging with the wavelength as its fourth dimension.

The use of volume and phase holographic elements in the design of photovoltaic solar concentrators has become very popular as an alternative solution to refractive systems, due to their high efficiency, low cost and possibilities of building integration. Angular and chromatic selectivity of volume holograms can affect their behavior as solar concentrators. In holographic lenses, angular and chromatic selectivity varies along the lens plane. Besides, considering that the holographic materials are not sensitive to the wavelengths for which the solar cells are most efficient, the reconstruction wavelength is usually different from the recording one. As a consequence, not all points of the lens work at Bragg condition for a defined incident direction or wavelength. A software tool that calculates the direction and efficiency of solar rays at the output of a volume holographic element has been developed in this study. It allows the analysis of the total energy that reaches the solar cell, taking into account the sun movement, the solar spectrum and the sensitivity of the solar cell. The dependence of the recording wavelength on the collected energy is studied with this software. As the recording angle is different along a holographic lens, some zones of the lens could not act as a volume hologram. The efficiency at the transition zones between volume and thin behavior in lenses recorded in Bayfol HX is experimentally analyzed in order to decide if the energy of generated higher diffraction orders has to be included in the simulation.

Satellite Laser Ranging Systems typically operate on the second harmonic wavelength of a pulsed Nd:YAG laser at a wavelength of 532 nm. The absence of sufficiently sensitive photo-detectors with a reasonably large active area made it beneficial to trade the conversion loss of frequency doubling against the higher quantum efficiency of the detectors. Solid state silicon detectors in the near infra-red regime at λ = 1.064 µm also suffered from high thermal noise and slow signal rise times, which increased the scatter of the measurements by more than a factor of 3 over the operation at λ = 532 nm. With the availability of InGaAs/InP compound - Single Photon Avalanche Diodes the situation has changed considerably. Their quantum efficiency has reached 70% and the compound material of these diodes provides a response bandwidth, which is commensurate with high high speed detectors in the regime of 532 nm. We have investigated the properties of such a diode type Princeton Lightwave PGA-200-1064 for its suitability for SLR at the Nd:YAG fundamental wavelength with respect to the quantum efficiency and their timing properties. The results are presented in this paper. Furthermore, we provide remarks to on the performance of the diode compared to state of the art detectors, that operate at the Nd:YAG second harmonic wavelength. Finally, we give an estimate of the photoelectron statistics in satellite laser ranging for different operational parameters of the Wettzell Laser Ranging System.

The multi-tone amplification for the purpose of mitigating stimulated Brillouin scattering (SBS) effect is investigated. Different wavelengths and power ratio are considered in the simulation model to achieve optimal results. The numerical simulation results indicate that SBS is effectively suppressed in a fiber amplifier with an output from 53.7W to 96.9W by utilizing this approach.

According to the principle of reflectivity measurement using cavity ring-down spectroscopy, the origin of reflectivity measurement uncertainty was analyzed, we particularly discussed the origin of ring-down time measurement uncertainty, and concluded that the maximum amplitude selection of ring-down curve, the fitting of curve, the time delay of detector, and the dispersity of measurement results were the reasons why. Based on the cavity ring-down spectroscopy method, we built a reflectivity measurement system with the wavelength of 1.319 micron, and obtained the ring-down times of straight and folded cavity respectively. According to the origin of uncertainty, the extensional uncertainty of system was obtained. The result showed the high precision of reflectivity measurement using cavity ring-down spectroscopy.

A real-time method based on laser scattering technology was used to detect the interaction process of GaAs with a 1080 nm laser. The detector collected the scattered laser beam from the GaAs wafer. The main scattering sources were back surface at first, later turn into front surface and vapor, so scattering signal contained much information of the interaction process. The surface morphologies of GaAs with different irradiation times were observed using an optical microscope to confirm occurrence of various phenomena. The proposed method is shown to be effective for the real-time detection of GaAs. By choosing a proper wavelength, the scattering technology can be promoted in detection of thicker GaAs wafer or other materials.

The SG II 5PW laser is designed as an open ultra-short high power laser facility that operates at the wavelength of 808nm. Three optical parametric chirped pulse amplification (OPCPA) stages are used to ensure the uncompressed pulse energy up to 260J. With a four pass zigzag compressor, the pulse width is compressed into less than 30fs and the pulse energy about 150J. By using BBO and LBO crystal, the first two OPCPA amplifiers have been accomplished this year. 35J@21fs outputs have been achieved. Since the largest size of the LBO crystal now is only about 100mm×100mm that is not enough for the needs of the third OPCPA amplifier. In our work, potassium deuterium phosphate (DKDP) as a candidate crystal has been studied theoretically and experimentally. Phase-matching parameters for various deuterium doped rate DKDP crystals are calculated. OPCPA amplifier based on 95% deuterium doped rate is designed and the output characteristics are simulated by OPA coupled wave equations. The results show that DKDP crystals with deuterium doped rate higher than 90% can be utilized in ultra-short high power laser systems that support the pulse width shorter than 30 femtoseconds. Still by estimation, when Quasi-phase-matching techniques and collinear design are used in small signal OPCPA amplification, the greatest efficiency can reach above 55%. By experiment it has proved that the output spectrum width can be more than 80nm.

Relations among absorption of pump beam, quantum defect and thermal load were investigated for pump wavelengths of 968 nm and near 940 nm in two independent, real-time measurement experiments complemented with thermal distribution simulation. Saturation of absorption at 969 nm pumping for non-lasing operational regime, which affects temperature rise and exists independently of the thin disk type, disk head construction, pump power and pump beam diameter is reported. Disk temperature dependence of absorption, quantum defect and disk geometry and large difference between absorption, disk temperature and o-o efficiency at both pump wavelengths are discussed.

There is a strong push worldwide to develop multi-Joule femtosecond duration laser pulses at wavelengths around 3.5-4 and 9-11μm within important atmospheric transmission windows. We have shown that pulses with a 4 μm central wavelength are capable of delivering multi-TW powers at km range. This is in stark contrast to pulses at near-IR wavelengths which break up into hundreds of filaments with each carrying around 5 GW of power per filament over meter distances. We will show that nonlinear envelope propagators fail to capture the true physics. Instead a new optical carrier shock singularity emerges that can act to limit peak intensities below the ionization threshold leading to low loss long range propagation. At LWIR wavelengths many-body correlations of weakly-ionized electrons further suppress the Kerr focusing nonlinearity around 10μm and enable whole beam self-trapping without filaments.

As infrared (IR) imaging technologies improve for the commercial market, optical filters complementing this technology are critical to aid in the insertion and benefit of thermal imaging across markets of industry and manufacturing. Thermal imaging, specific to shortwave infrared (SWIR) through longwave infrared (LWIR) provides the means for an observer to collect thermal information from a scene, whether being temperature gradients or spectral signatures of materials. This is beneficial to applications such as chem/bio sensing, where the identification of a chemical species being present or emitted could compromise personnel or the environment. Due to the abundant amount of information within an environment, the difficulty lies within the observer’s ability to extract the information. The use of optical filters paired with thermal imaging provides the means to interrogate a scene by looking at unique infrared signatures. The more efficient the optical filter can either transmit the wavelengths of interest, or suppress other wavelengths increases the finesse of the imaging system. Such optical filters can be fabricated in the form of micro-spheres, which can be dispersed into a scene, where the optical filter’s intimate interaction with the scene can supply information to the observer, specific to material properties and temperature. To this extent, Lumilant has made great progress in the design and fabrication of such micro-sphere optical filters. By engineering the optical filter’s structure, different optical responses can be tuned to their individual application.

This manuscript describes a mobile stand-off detection and identification of trace amounts of hazardous materials, specifically explosives. The technique utilizes an array of tunable infrared quantum cascade lasers as an illumination source which spans wavelengths from 6 to 11 μm, operated at eye-safe power levels. This spectral range enables excitation of a wide variety of absorption bands present in analytes of interest. The laser is modulated to produce a 50% duty cycle, square wave pulses, and control the frequency of irradiation. The backscatter and photo-thermal signals from samples are measured via an IR focal plane array, which allows for the observation of spatial, temporal, and thermal surface processes. A discussion of how these signals are collected and processed for use in identification of hazardous materials is presented.

We report on a standoff chemical detection system using widely tunable external-cavity quantum cascade lasers (ECQCLs) to illuminate target surfaces in the mid infrared (λ = 7.4 – 10.5 μm). Hyperspectral images (hypercubes) are acquired by synchronously operating the EC-QCLs with a LN 2 -cooled HgCdTe camera. The use of rapidly tunable lasers and a high-frame-rate camera enables the capture of hypercubes with 128 x 128 pixels and >100 wavelengths in 2 area at 5-m standoff. Raw hypercubes are post-processed to generate a hypercube that represents the surface reflectance relative to that of a diffuse reflectance standard. Results will be shown for liquids (e.g., silicone oil) and solid particles (e.g., caffeine, acetaminophen) on a variety of surfaces (e.g., aluminum, plastic, glass). Signature spectra are obtained for particulate loadings of RDX on glass of 2 .

Nanostructure-based surface plasmon resonance (SPR) sensors are capable of sensitive, real-time, label-free, and multiplexed detection for chemical and biomedical applications. Recently, the studies of nanostructure-based aluminum sensors have attracted a large attention. However, the intrinsic properties of aluminum metal, having a large imaginary part of the dielectric function and a longer electromagnetic field decay length, limit nanostructure’s surface sensing capability. To improve the surface sensitivity, a nearly guided wave SPR sensor has been proposed, which enables the surface plasmons to spread along the dielectric layer and increases the interaction volume. Here we proposed the combination between Fano resonances in capped nanoslits and a thin nanodielectric top layer to develop highly sensitive nanostructure-based aluminum sensors. We studied the effects of an Al 2 O 3 protection layer on the optical properties, bulk and surface (wavelength and intensity) sensitivities of capped aluminum nanoslits. We found the top layer can enhance the sensitivities of the Wood’s anomaly-dominant resonance or asymmetric Fano resonance in capped aluminum nanoslits. The maximum improvement can be reached by a factor of 16. The maximum wavelength and intensity sensitivities are 6.8 nm/nm and 150 %/nm, respectively. With 1.71 % intensity change (3 times of noise level), the limit of detection of Al 2 O 3 film thickness was 0.018 nm. We attributed the enhanced surface sensitivity for capped aluminum nanoslits to a reduced evanescent length and sharp slope of the asymmetric profile caused by the capped oxide layer and Fano coupling. The protein-protein interaction experiments verified the high sensitivity of the Al 2 O 3 -aliminum capped nanoslits.

Deep-ultraviolet Raman spectroscopy is a very useful approach for standoff detection of explosive traces. Using two simultaneous excitation wavelengths improves the specificity and sensitivity to standoff explosive detection. The High Technology Foundation developed a highly compact prototype of resonance Raman explosives detector. In this work, we discuss the relative performance of a dual-excitation sensor compared to a single-excitation sensor. We present trade space analysis comparing three representative Raman systems with similar size, weight, and power. The analysis takes into account, cost, spectral resolution, detection/identification time and the overall system benefit.

Aluminum Oxynitride (ALON® Transparent Ceramic) and Magnesia Aluminate Spinel (Spinel) combine broadband transparency with excellent mechanical properties. Their cubic structure means that they are transparent in their polycrystalline form, allowing them to be manufactured by conventional powder processing techniques. Surmet has scaled up its ALON® production capability to produce and deliver windows as large as 4.4 sq ft. We have also produced our first 6 sq ft window. We are in the process of producing 7 sq ft ALON® window blanks for armor applications; and scale up to even larger, high optical quality blanks for Recce window applications is underway. Surmet also produces spinel for customers that require superior transmission at the longer wavelengths in the mid wave infra-red (MWIR). Spinel windows have been limited to smaller sizes than have been achieved with ALON. To date the largest spinel window produced is 11x18-in, and windows 14x20-in size are currently in process. Surmet is now scaling up its spinel processing capability to produce high quality window blanks as large as 19x27-in for sensor applications.