This PDF file contains the front matter associated with SPIE Proceedings Volume 11105, including the Title Page, Copyright information, Table of Contents, Author and Conference Committee lists

Publisher’s Note: This conference presentation and paper, originally published on 9 September 2019, was withdrawn on 13 May 2020 per author request.

Ultrasonic mechanical vibrations in solids are widely used in non-destructive testing, and high-power applications such as ultrasonic welding or soldering. The visualization of ultrasonic wave propagation in transparent solids is helpful for understanding the ultrasonic behaviours. The classical method of photoelasticity allows the visualization of the static stress distribution in birefringent materials. Utilizing recent high-power LEDs in the photoelasticity allows to capture dynamic stresses by high frequency stroboscopic light. High frequency stationary and transient oscillation processes in elastic solids can be visualized with this method. The designed LED array in this paper has a dimension of 210 mm_300 mm, and every LED has distance of 38mm to each other, and the light intensity has a homogeneity value. The temporal and spatial resolution of stress-optic systems depends mainly on the dynamic properties of the lighting technology used. The high speed synchronization of the stroboscopic light sources results in a high temporal resolution of the photoelasticity analyses. This enables the photoelastic investigation of highly dynamic load conditions, such as longitudinal waves and transverse waves.

Photoacoustic tomography seeks to reconstruct an acoustic initial pressure distribution from the measurement of the ultrasound waveforms. Conventional methods assume a-prior knowledge of the sound speed distribution, which practically is unknown. One way to circumvent the issue is to simultaneously reconstruct both the acoustic initial pressure and speed. In this article, we develop a novel data-driven method that integrates an advanced deep neural network through model-based iteration. The image of the initial pressure is significantly improved in our numerical simulation.

Modern 3D-printing technologies allow for the production of very small and complex microscale optical systems, which require examination of wave-optical effects within their design process. Common optical design software employs ray-tracing as their basic concept, which is not capable of fully simulating wave-optical effects. Rigorous methods, which solve electromagnetic field equations, are very time consuming and require more proficiency of the users. We present an application of the Wave Propagation Method (WPM), which is able to accurately simulate wave-optical effects in forward direction, while providing a reasonably fast calculation time utilizing both central- and graphics processing units (CPU and GPU) as an easy-to-use plugin for the open-source software ITOM.

We experimentally report a normalized differential signal processing technique to improve the signal-to-noise ratio (SNR) of a fiber optic distributed acoustic sensor (DAS), in the time-domain. The introduced method is calibrated through comparing it with the typical differential method when using a noisy DAS system that includes a relatively wide linewidth laser. For this system, the normalized differential method allows measuring the vibration locations, produced by a piezoelectric transducer (PZT) cylinder, with enhanced SNR.

Recently, we have proposed the pairing of Deep Neural Networks and evolutionary algorithms as a versatile route for the optimal design of optical devices and systems.¹ Here, we extend that work and investigate the use of deep Convolutional Neural Networks (CNN) as opposed to fully connected feedforward architectures. We show that networks built with convolutional layers, batch normalization (BN), parametric REctified Linear Unit (ReLU) and residual blocks achieve drastic reduction in parameter weights and training epochs in comparison to dense, fully-connected networks for comparable accuracy. The proposed lightweight CNNs when used for approximate objective evaluation in concert with DE global optimization resulted in nearly 8x speedup in convergence time. The choice of a network architecture and optimization of its hyperparameters is a tedious task and it is hoped that the systematic hyperparameter search reported here would assist others in faster model selection.

In even the cleanest of environments, surfaces in optical systems are susceptible to the collection of dust. Because scattering from such contaminants can interfere with the intended operation of the system, it is important to consider their effects during the design via modeling and simulation. A standard developed by the Institute of Environmental Sciences and Technology (IEST) is most commonly used to define the typical sizes and density of particulates on a surface, which can then be used to create a BSDF profile of the contaminated surface. This BSDF profile can be applied to the smooth surfaces within a model to simulate the effects of the contaminants, making up a critical part of the stray light analysis for an optical system. The limitation of such an approach, however, is that the scattering events occur stochastically, with no spatial consistency. In this work a modeling approach is examined that considers the particulates to be stationary on the surface which is more realistic. With the particulates stationary, it is possible to isolate the effects of an individual particle, which can be especially useful for small scale systems. A variety of application designs are investigated through the use of computer simulation to demonstrate the advantages of the isolated contamination scattering approach.

We present the general formula to generated freeform collimator lens free of spherical aberration and astigmatism. The presented formula describes the second surface of the freeform singlet such as it correct the spherical aberration generated and astigmatism by the first surface of the singlet.

We reported previously on novel methods for designing optical systems with no prior specification of system architecture (e.g., number and type of lenses and their order in the optical train). We studied their efficacy on a set of problems where aberration minimization at the focal plane was the only design objective. Here, we describe enhancements that allow multiple additional objectives (e.g., system sensitivity, size, cost) to be included in a principled manner and show how a family of non-dominated" systems that approximate the set of designs belonging to a theoretical Pareto front of optimal solutions may be efficiently created.

The correction of aberrations is fundamental in optical systems, and one can use lenses with aspheric surfaces, free form surfaces, diffractive optics, metasurfaces, and gradient-index (GRIN) media. Here we propose to use a GRIN structure for correcting spherical aberration and coma in an afocal system. The complexity of having GRIN lenses in the system is balanced by the fact that the external lens surfaces are spherical, for both GRIN lenses are spherical and concentric to one common point, the intermediate focal point. For collimated light, each lens is free from spherical aberration. The whole system can also be free from coma aberration if the Abbe Sine Condition (ASC) is fulfilled. To create an aplanatic afocal system, it is necessary to have a constant ratio between the heights of the incoming and outgoing rays for all rays in the axial beam, so that the angular magnification of the system is preserved. The afocal system presented in this paper has been designed using geometrical optics. An analytical expression to satisfy the ASC has been derived by matching the central refractive index value of the outer surfaces lenses. The system consists of one positive and one negative GRIN lens with their inner surfaces being concentric to the intermediate focus. The angular magnification m is given by the ratio of the radius of curvature of the front surface of the first lens and that of the back surface of the second lens and in our example has been chosen as m = 2.

In this work we propose and implement the use of software defined optical interferometry for the development of laser ultrasound non-destructive testing. The interferometer is conceived as an optoelectronic system that can be controlled by software. The system itself consists of five interconnected blocks: an optical system (a heterodyne interferometer), an Electrical-Optical block (a laser + an acousto-optic modulator), an Optical-Electrical block (a balanced photodetector), a software defined hardware (a software defined radio platform), and a programmable controller (a personal computer). In particular, the selected software defined hardware includes a field programmable radio frequency transceiver. On the one hand, it can synthesize the stimulus signals for the acousto-optic modulator which splits the reference and test beams. On the other hand, it can process the photo-detected high-frequency signals accordingly. This software defined radio platform not only simplifies the experimental scheme but also has such a high sensibility that provides a wide dynamic range. In order to show the performance of the system for non-destructive testing, we analyze the signals produced on aluminium plates to detect flaws in weld seams.

The light field describes the radiance at a given point provided by a ray coming from a particular direction. Integrating the light field for all possible rays passing through that point gives total irradiance. For a static scene, the light field is unique. Cameras act as integrators of the light field. Previously, it was demonstrated that freeware rendering software can be used to simulate the light field entering an arbitrary camera lens. This is accomplished by placing an array of ideal pinhole cameras at the entrance pupil location and rendering. The pinhole camera images encode the ray directions for rays passing through the pinholes. The set of images from this array then describes the light field. Images for real camera lenses with different types of aberrations are then simulated directly from the light field. The advantage of this technique is that the light field only needs to be calculated once for a given scene. Calculation of the light field is computationally expensive and the practicality of implementing high resolution light field simulations on a desktop computer is limited. However, cloud-based rendering services with arrays of CPUs and GPUs are now readily available and affordable. These services enable more realistic simulations and different scenes to be rapidly created. Here, the techniques are demonstrated for different real lens aberration forms.

New, moldable IR glasses from NRL and Graded index (GRIN) optics enable simultaneous imaging across multiple wavebands including SWIR/MWIR/LWIR and offer potential for both weight savings and increased performance. Optical properties databases compatible with Zemax and CodeV will be presented and made available for users. Lens designs show the potential for significant SWaP reduction benefits and improved performance using NRL materials and IR-GRIN lens elements in multiband sensors. The SWaP and performance advantages of these materials will be presented.

Thermal modeling using equivalent circuits in analogy to electrical circuits is a well-established technique, especially in modeling power dissipation in electronic devices and optimizing cooling means. In building construction and facility energy management, these methods still are rarely found: circuit based models are the exception in this field. The inclusion of thermal radiation effects in energy efficiency optimization - especially for insulation structures - is often omitted, although thermography is widely used. Contrary to pure numerical simulations, equivalent circuit methods allow the derivation of useful formulas and rules of thumb. It might be expected that the thermal optimization of buildings in near future will rely on every percentage of potential savings, so the inclusion of thermal radiation into rules of thumb might be a consequence. In the paper we present a short review on such methods. As examples drawn from current research, we discuss applications in facade and roof construction. While the specific problems discussed here are derived from investigations of energy efficiency in building construction, the focus of the paper is on the applied methodology of thermal modeling and its optical aspects. It is understood as a short tutorial paper.

In this presentation, we will describe the design, fabrication and characterization of flat lenses that operate in any desired spectral regime. Specifically, we will describe flat lenses in the visible band, in the visible and near-IR band, and also in the LWIR band. We have shown that multi-level diffractive optics, when designed properly can enable high efficiency broadband imaging [1]. Here, we will extend the performance to the IR and show experimental results. We further compare our optics with metalenses, and emphasize that metalenses offer no additional advantage [2]. In fact, metalenses are far more challenging to fabricate. Please refer to papers below for details. [1] M. Meem, A. Majumder and R. Menon, “Full-color video and still imaging using two flat lenses,” Opt. Exp. 26(21) 26866-26871 (2018). [2] S. Banerji, M. Meem, B. Sensale-Rodriguez and R. Menon, “Imaging with flat optics: metalenses or diffractive lenses?,” arXiv:1901.05042 [physics.optics]

Traditional polarization gratings (PGs) have been studied with increasing intensity since 2005, in part because they can manifest 100% single-order diffraction efficiency and strong sensitivity to input polarization, in both theory and practice. They can be made using patterned anisotropic materials (e.g., liquid crystals) or nanostructures (e.g., metasurfaces). Nearly every prior work on traditional PGs has implemented a linear spatial phase-shift that is either continuous or which samples the 2π phase period with multiple (≥ 4) discrete phase levels. As far as we know, only two prior works (Bhandari et al, Phys. Rep. 281 (1997); and Wang et al, Appl. Phys. Lett. 108 (2016)) have considered the circumstance when the phase is sampled with exactly two phase levels, with π radians between them. We call this a Binary PG (Bin-PG). In this work, we apply Jones calculus and the small angle (i.e., paraxial) approximation to derive the fundamental optical behavior of Bin-PGs: far-field efficiencies, input polarization sensitivity, and output polarizations. We show that Bin-PGs manifest properties that are a compelling and unique mixture of both traditional (non-binary) PGs and standard diffraction gratings (e.g., surface-relief-gratings (SRGs)). Like non-binary PGs, their output polarization is often different than the input and diffraction efficiencies are dependent on the effective retardation of the film or surface. However, like SRGs, they show a maximum of 80% total first-order efficiency and are insensitive to input polarization.

In this report an infrared zoom optical system is discussed. This system shifts a single moving element to switch between two focal lengths(30mm/60mm), one for wide angle and the other for close-up. However, a conventional optics-only method cannot provide good imaging quality over a large depth of focus at each focus offset. To improve the imaging performance, we investigate a lens-combined modulated wavefront coding technology for extending the depth of focus. Instead of placing a phase mask at the pupil position like traditional wavefront coding does, all the element surfaces in the system contribute to achieving modulation transfer function (MTF) consistency over a large range of depth of focus under dual field-of-view settings. As a result, the new structure extends the depth of focus 6.5 times than that of the original system. We also demonstrate recovered images employing hyper-Laplacian priors with noise and artifacts suppressed. It is concluded that the novel structure can not only extend the depth of focus but also reduce the complexity of infrared optical system.

A novel optical polarimetry technique for performing non-invasive glucose monitoring is proposed. In the proposed approach, a differential Mueller matrix polarimetry technique is used to extract the optical rotation angle and depolarization index of the sample. The glucose concentration of the sample is detected by sensing the change in the polarization plane of the incident light as it passes through the sample. The feasibility of the proposed technique is demonstrated by measuring the glucose contents of phantom solutions with known glucose concentrations in the range of 0~500 mg/dL by using two different Stokes-Mueller matrix polarimetric measurement systems. The practical applicability of the proposed technique is confirmed by measuring the glucose concentration of mice.

Multi-photon nonlinear laser wave-mixing spectroscopy is presented as an ultrasensitive detection method for pancreatic cancer biomarkers, carbohydrate antigen 19-9 (CA 19-9) and carbohydrate antigen 242 (CA 242), and heart-failure biomarkers, pro-atrial natriuretic peptide (proANP) and brain natriuretic peptide (BNP). Wave mixing is an ultrasensitive optical absorption-based detection method, and hence, it can detect both fluorescing and non-fluorescing biomarkers. One can detect biomarkers in their native form, label-free, without the use of time-consuming labeling steps. The wave-mixing signal beam is strong, collimated and coherent (laser-like) and it can be collected using a simple photodetector with an excellent signal-to-noise ratio (S/N). The wave-mixing signal has a quadratic dependence on the analyte concentration, and thus, small changes in analytes can be monitored more effectively (i.e., an ideal sensor). Compared to currently available detection methods, wave mixing offers inherent advantages such as short optical path length (micrometer-thin samples), high spatial resolution, ultrasensitive detection limits comparable or better than those of fluorescence- or ELISAbased methods, and native label-free detection. Since laser wave-mixing probe volume is small (nanoliter to picoliter), it is intrinsically convenient to couple with microfluidics or capillary-based electrophoresis systems to enhance chemical specificity. Different biomarkers can be placed on a simple slide or flowed inside a capillary and then detected. Our nonlinear multi-photon detectors can be easily configured as portable battery-powered devices that are suitable for use in the field. Potential real-world applications include detection of various biomarkers, cancer cells, and reliable early detection of diseases.

This work presents a first prototype for a new approach to microscopy: a system basing its resolving power on the light emitters instead of the sensors, without using lenses. This new approach builds on the possibility of making LEDs smaller than current technology sensors, offering a new approach to microscopy we plan on developing towards superresolution. The microscope consists on a SPAD based camera, a 8x8 LED array with 5x5 μm LEDs distributed with a pitch of 10 μm, and discrete driving electronics to control them. We present simulations of the system, as well as the first microscope prototype implementing the method, and the results obtained through it.

Severe sepsis accounts for a third of patient deaths in the intensive care units worldwide therefore early sepsis detection and therapy onset is crucial for reduction of patient mortality and expenditures. In the present study the device prototype for sepsis bedside diagnostics is proposed, by combining hyperspectral and thermal imaging. The diagnostic principle is based on evaluation of skin oxygenation and micro perfusion inhomogeneity. Preliminary results confirm early heterogeneity detection of skin oxygenation (hemoglobin saturation with oxygen) and temperature caused by oxygen utilization and blood perfusion impairments. The present findings indicate on high sensitivity of developed prototype compared to routine subjective visual assessment of patient’s skin by clinicians.

Particle accelerators are central to applications ranging from high-energy physics to medical treatments. However, the cost and size of conventional accelerators operating in radio-frequencies is prohibitive for widespread proliferation. Operating at optical and near-infrared frequencies, dielectric laser accelerators (DLAs) leverage the high damage threshold of dielectric materials, advances in nanofabrication techniques, and femtosecond pulsed lasers to produce miniaturized laser-driven accelerators. Previous demonstrations of dielectric laser acceleration have utilized free-space lasers directly incident on the accelerating structure. While this is acceptable for proof-of-principle, for DLAs to become a mature technology, it is necessary to integrate the accelerators on-chip to increase scalability and robustness of the system. Here we demonstrate the first waveguide-integrated dielectric laser accelerator. In this scheme, a grating coupler is used to couple light from femtosecond pulsed laser to a 30 μm wide waveguide, fabricated on a silicon-on-insulator platform. The waveguide is then directly interfaced with an accelerating structure that is patterned with sub-wavelength features to produce near-fields phase-matched to electrons travelling through a vacuum-channel in the device. Both the input grating coupler and accelerator structure have been designed using the inverse design optimization approach. We have experimentally demonstrated these waveguide-integrated accelerators by showing acceleration of subrelativistic electrons of initial energy 83.5 keV. We observe a maximum energy modulation of 1.19 keV over 30 μm. These results represent a significant step toward scalable and integrable on-chip DLAs for applications in ultrafast, medical, and high-energy technologies.

In recent years, as demand for high speed communication with advanced technology is increasing in optical communicat ion,so optical logic gates are being widely investigated for various applications in signal processing such as optical binary adder, optical counters, optical time division mult iplexing and low power computing etc. In the proposed work we have demonstrated the implementation of different logic gates such as AND, OR, XOR, XNOR, NAND and NOR which are the basic components to design any combinational and sequential circuits using Mach Zehnder Modulator (MZM). The MZM minimizes the effect of dispersion and provides the fast switching for high speed optical communicat ion. The MZM is used for controlling the amplitude of optical wave by applying voltage that introduced phase shift in the wave passing through the arm. This allows us to switch the output power from high to low or vice - versa (from login 1 to 0 or vice-versa). The proposed optical logic gates using MZM has low complexity and high scalability.

Slow light photonic crystal waveguides (PCW) are a promising tool for optical signal processing as well as integrated optical devices that require strong light-matter interactions, such as modulators or non-linear devices. However, the low group velocity that characterizes these PCWs is typically accompanied by a large group velocity dispersion (GVD), and a low coupling efficiency. Improving both these properties for a large bandwidth forms the design challenge of most optical devices that rely on PCWs. In this work, we use inverse design methods to, firstly, design slow light PWCs with a large group index-bandwidth product (GBP), and secondly, to design couplers for the PCW, i.e. a mode converter, which couples a ridge waveguide to the PCW, and a grating coupler, which couples free space light directly to the PCW slow light mode. Both couplers are optimized for the PCW’s low group velocity dispersion bandwidth. Unlike pre-existing work, we perform the PCW optimization in full 3D simulations which result in more accurate and fully fabricable devices. The high degrees of freedom associated with inverse design makes it an effective method for these problems and, as such, an essential design tool to optimize future PCW applications.

Nanophotonic devices, such as CMOS image sensor (CIS) pixels, are formed by stacking multiple layers of semiconductor materials. The complex refractive indices of these materials vary with the wavelength of light. Currently, industrial development of photonic devices includes a design step where light propagation is simulated using numerical methods, such as finite-difference time-domain (FDTD). Such simulations require that the refractive indices of the constituent materials be known accurately.

Most commonly employed methods for computing the real and imaginary parts of the dispersive refractive indices are based either on the evaluation of the Kramers-Kronig (K-K) integral, or on the use of theoretical models of permittivity. These methods rely on the experimentally measured reflectivity or transmissivity spectra of thin films of a material to determine its refractive indices.

In the first part of this paper, we describe the computation of the dispersive refractive indices of certain materials using an optimization routine based on a genetic algorithm and the coherent reflectivity and transmissivity spectra of thin-films. This approach finds the global optimum unlike earlier methods based on local optimization techniques. In the second part of the paper, we evaluated the K-K integral and used the Lorentz model of permittivity to compute the real part of the refractive index of Rhodamine B from its imaginary part. The imaginary part was determined from the transmission spectrum of a thin film of Rhodamine B. Recently, we used a similar strategy to compute the dispersive refractive index of an on-chip color filter commonly used for CIS pixel.

NASA Langley has been developing the High-Altitude Lidar Observatory (HALO) as a multi-function lidar and testbed to advance the technology needed for airborne and space-based measurements of methane and other gases. These measurements have been identified in the 2018 Earth Science Decadal Survey as a candidate for Explorer class space-based measurements. A laser transmitter capable of generating the online and offline wavelengths needed for the differential absorption lidar (DIAL) measurements of methane is key component of the HALO system. Fibertek has recently developed the required single-frequency laser transmitter operating in the 1645 nm region for methane measurements. It incorporates the pumping of a seeded optical parametric oscillator with a kHz class single-frequency 1064 nm pump laser. The fielded system can generate 1645 nm seeded output of 2 mJ/pulse at 1 kHz. The laser has been successfully incorporated into the HALO system and used in airborne field measurements. We will discuss the design and performance of this laser and the lessons learned from our development activities.

Directional Coupler (DC) is one of the vital components in integrated optics and optical communication which is used to exchange optical power between the two adjacent waveguides due to the modal interaction. Broadband DC can be used to replace fiber couplers in optical coherence tomography (OCT). OCT is non-contact imaging modality having numerous applications in bio-medical and non-bio-medical imaging. Retinal imaging is one of the significant applications of OCT which works in the visible and near infrared (NIR) domain below 1 micron. In integrated optics, silicon nitride (SiN) as core material exhibits high transmission values down to 0.4 micron. Using SiN waveguides, a broadband photonic integrated DC at 850nm has been designed. Parameters such as coupling length and coupling spacing for a 50:50 splitting ratio have also been analyzed. A novel asymmetric broadband DC having an asymmetric coupling section at 850nm has also been designed. This structure is broadband over 100nm bandwidth and shows better results in terms of normalized splitting ratio and excess loss. The accuracy of our structure has been validated by using commercially available Fimmwave Photon Design software. The calculations were performed for transverse electric (TE), transverse magnetic (TM) and fully vectorial mode types and maximum excess loss reported for all 3 types was accounted to be less than 0.2dB. With further optimization in design and technology, SiN waveguides are potential candidates for passive photonic integrated circuits for OCT.

ColdQuanta’s microShutter is a free-space, chip-scale mechanical shutter designed for laser shuttering applications. The microShutter breaks through the size constraints of MEMS fiber shutters by eliminating the optical fiber and operating on the beam inline and in free-space. The microShutter allows laser shuttering in a form factor and with a power budget that enables high performance optical applications in hand-held devices. Uniquely, each microShutter chip integrates a beam dump that captures stray light in an on-board light trap. The microShutter is designed to the power, performance, and size requirements of portable atomic clocks and other compact atomic systems requiring free-space optical distribution. The prototype chip has been demonstrated to draw less than 0.5 μA at 150 V. A low power driver circuit that can operate the microShutter with 2.5 mW with a 4V supply has been demonstrated. Early prototypes demonstrate extinction below -45 dB with insertion loss of -2 dB, an open-closed transition time of 12 μs and closed-open transition time of 14 µs.

Light detection and ranging (LiDAR) is an important technique for three-dimensional environment reconstruction that is useful for self-driving car, robotic vehicle, agriculture detection and blind guidance. Beam steering in the current LiDAR is accomplished by a mechanical spinning architecture, which is heavy, slow and expensive. Micro-electrical-mechanical system (MEMS) built mirror is an alternative solution to reduce size and cost. However, the mechanical beam steering in both techniques cause reliability issues in long-term precise beam positioning that limit the broad application of the LiDAR. Optical phased arrayed (OPA) comprise periodic placed emitters with coherent light output by using Silicon photonics. The beam steering in the OPA is accomplished by the interference of coherent light that has no moving parts. Each emitter is modulated and delayed by a pre-determined phase that cause the maximum light intensity has an angle to the emitter plane. This angle is determined by the phase difference in each emitter. Therefore, the beam steering is implemented and controlled by the phase adopted. However, according to the interference theory, second and high-order maximum, the side-lobes, appear at different angles that confuse the LiDAR system by multiple positioning at the same time. In addition, to implement wide angle beam steering, the large amounts of arrayed emitters should be applied. To keep coherent, multiple -3dB light coupling structure were applied. The wide distributed and non-uniform light output between emitters cause the beam steering disturbed. In this work, instead of wide angle beam steering, we design a linear optical phased array (LOPA) with limited number and closed-distance emitters for small angle beam steering. Practical-wise, multiple LOPA modules could be integrated to implement wide angle beam steering. Finite-element method was used to simulate the 1550 nm beam steering behavior in LOPA. With proper and minimal phase delayed, the intensity of the side-lobes was largely suppressed to the primary light. With proper tuning on the sensitivity of the receiver, the high-order disturbance in the LOPA for LiDAR could be eliminated.

We present a general analytic and close-form formula to determine the shape of a surface that corrects the spherical aberration generated by an arbitrary number of preceding surfaces in a refractive telescope.

In this work, a novel technique to create adaptive liquid crystal lenses and other optical components is proposed and demonstrated. This proposal avoid all of the previous techniques disadvantages, a simple fabrication process and low voltage control is required, and thin lenses can be obtained. The novelty of the proposal, resides in a micro-structured indium tin oxide, designed to transmit the voltage homogeneously across the entire surface of the active area. This design is composed of two main elements, a transmission line that generates a voltage gradient, and a series of combs that distribute the voltage across the entire active area. Two different apertures are designed. One of this designs is fabricated and measured to demonstrate the viability of the idea. This novel structure open new venues of research in phase-only LC optical devices.

Finger touch-based interactions relying on real physical touch between the objects and the plane screens are inconvenient to be used in large scale displays, since the size of the screen is beyond the reachable range of the operators. In this work, we propose a novel optical interaction simultaneously integrated with remote optical touch and direct touched fingerprint sensing which includes three layers of transparent optical films embedded with sub-wavelength gratings. The proposed films were validated by the rigorous coupled-wave theory analysis and the coupling efficiency of each layer was optimized via the finite difference time domain (FDTD) simulation. The proposed smart transparent optical interaction system is believed to improve the performance of touching technologies which have significant applications in large screen teaching, meeting and gaming.

his paper focuses on depth of field (DOF) extension through polarization aberrations. The addition of polarizing elements into an optical system allows to exploit the polarization of the incoming light as an additional degree of freedom in the optical system design. Two optical systems have been studied: the first characterized by the presence of polarizing thin film coated optical surfaces, the second based on the addition of an anisotropic birefringent waveplate into the path of light rays of an optical system. The polarization dependent DOF of these two systems are compared. It is shown that the effect of polarizing elements is similar to a polarization dependent apodization of the pupil.

Experimental studies within the statistical approach of the coordinate structure of the distributions of the intensity of own fluorescence of polycrystalline blood plasma films of patients of the following groups: control group of donors - group 1; patients with non-alcoholic fatty liver disease - group 2; patients with chronic hepatitis - group 3: The average values and ranges of variation of statistical moments of the 1st - 4th orders determined within the representative samples, which characterize the coordinate distributions of the intensity values of autofluorescent microscopic images of samples of polycrystalline blood plasma films within groups 1, 2, 3. The analysis of the operating characteristics of the power of the method of laser polarization mapping of two-dimensional distributions of the intensity values of its own fluorescence of microscopic images based on the determination of the sensitivity values, specificity and accuracy of the diagnostic test.

This report contains the results of approbations of the polarization correlometry method (PCM) – statistical mapping of biological tissues fractal structure (myocardium and brain - “fibrillar optically anisotropic networks” and the wall of the rectum - “island optically anisotropic structures”) and liquids (polycrystalline films of synovial fluid - a superposition of “structured and island networks of biological crystals").

The principles of the use of fractal analysis in the problems of polarization mapping of microscopic images of biological preparations are considered. Myocardial tissue of the deceased with various pathological and necrotic changes was selected as the object of study. A model of the polycrystalline structure of such an object is proposed. Obtained maps of the ellipticity of the polarization of microscopic images of such an object. Within the framework of fractal analysis, the statistical moments of the 1st - 4th orders were found, which characterize the distribution of the logarithmic dependences of the power spectra of polarization ellipticity maps. The criteria for differentiation of various pathological states of myocardial tissue are determined.

The materials of experimental studies of the coordinate and statistical structure of the coordinate distributions of the degree of local depolarization of coprofiltrate layers taken from patients of group 1 and group 2 are presented.

The interrelations between the values of the statistical moments characterizing the coordinate distributions of the degree of local depolarization of coprofiltrate layers and the physiological state of the patients within group 1 and group 2 are established.

An analysis of the operational characteristics of the power of mapping the coordinate distributions of the degree of local depolarization of coprofiltrate layers taken from patients of group 1 and group 2 based on the determination of sensitivity, specificity, accuracy, predictability of positive and predictability of a negative result is carried out from the standpoint of evidence-based medicine.

The results of statistical dependence and correlation structures of two-dimensional Mueller matrix elements in various spectral regions of laser radiation by changes in the distribution of orientations of optical axes and birefringence of protein crystals. Namely, a two-wave (“red-blue”) approach – layer of biological tissues irradiated by He-Ne laser (λ₁ = 0,63μm ) and He-Cd laser (λ₁=0,41μm )was used Conducted analysis of polarimetric sensitivity was made, a state of polarization points that contain volumetric structures of biological objects to spectral region of laser radiation was detected.

In this work, we show an optoelectronic system based on a plastic optical fiber (POF), which can detect changes in the RGB composition in liquid solutions. This system consists of a white light (LED) with 3 W of power, and 20 centimeters of POF with cladding in the U-configuration,where 0.5 cm is without cladding that allows having contact with the rest of the solution. Also, the arrangement of photodiodes allows us to capture the intensity of light that comes from the fiber. Furthermore, we tested different solutions where we observed changes in the RGB color composition, using different concentrations of water with alcohol. These results shall allow us to design in the future a prototype for measuring the refractive index in different liquid solutions.

In this numerical work, we present some cases of transmission behavior in a power-symmetric, polarization-imbalanced nonlinear optical loop mirror (NOLM) through a three-dimensional (3D) analysis. The study has been implemented using the Jones matrices for inputs at linear and circular polarization and varying the length in the loop. The results show control over the switching power and the maximal transmission, which let us see more easily the graph visualization at the output of a scheme. However, we can determine the characteristics of the experimental operation (fiber loop, input power, angles of the retarder plates, critical power, and input polarization). These results can be used to establish regions for potential applications in optical communications such as ultrafast optical signals processing, optical switching, demultiplexing, filtering, logic gates, and pulse compression.

Laser guide stars (LGSs) are fundamental elements of adaptive optics. They indeed allow to form an artificial star in the sky, which is used as a reference for the compensation of the effect of atmospheric perturbation on wave fronts. This paper describes the design principle of laser guide stars and in particular show the advantage of using a combination of two afocal systems. Indeed, the first afocal can be used, with controlled defocus, to tune the size and position of the beam waist at the entrance of the second afocal. This allows, for example, to decrease the ultimate size of the artificial star which can be achieved. Moreover, it also allows to set parameters so that tolerances of the system are released.

For remote data acquisition, the integration of optical and electronic instrumentation systems (OSA, oscilloscope, polarimeter) is proposed, reaching automation through control protocols (TCP/IP). A graphical interface was developed through the LabVIEW virtual environment, using MATLAB to present the results of accumulated spectra and temporal evolutions. Using our automated data acquisition system, we analyze in detail the operating characteristics and stability at the output of a passively mode-locked fiber laser (figure-eight laser, F8L), looking to expand the study on the evolution of the polarization and the behavior of the pulses according to the adjustment of the polarization control plates included in the laser cavity.

We present a compact catadioptric lens for use in smartphone iris imaging. With an emphasis on object-space resolution, this lens has a large aperture. To fit within typical shallow phone casing, the lens is folded axially, with the folding arrangement inspired by the Maksutov telescope; the resulting z-height is less than 5.5 mm. Two mirrors give a double ray path, with the secondary mirror centrally obscuring the lens aperture. Using a single refracting element, axial chromatic aberration is limited by using low-dispersion glass. Aspheric coefficients are used on all surfaces, for aberration compensation. The refocussing lens is designed to focus on a nearest object at −300 mm, with refocus achieved by a small axial shift of the primary mirror. The polychromatic MTF is above 0.4 across a 16-degree full field-of-view (FoV) for iris distances as large as −500 mm, for the near-infrared wavelengths of 920 ±35 nm. While the FoV is limited by the catadioptric arrangement, it is sufficiently large for this specialized application. This can be justified by considering that the human interpupillary distance is such that the two eyes subtend a full FoV of 8-deg or less at the closest distance of −300 mm.

Cubic phase wavefront coding technique is applied to an imaging system with the aim of extending the depth of field (DOF). The design is based on the wavefront coding method proposed by Dowski and Cathey¹. The method employs a cubic phase mask (CPM) to modify the point spread function (PSF) of the imaging system under incoherent illumination such that the PSF of the system is formed as an isosceles right triangle, which makes the PSF insensitive to defocus. Researchers have found the optimized values of cubic phase coefficient and the exit pupil distance for the given specifications for solving wavefront coded task-based imaging problem². The extended DOF design is usually based on placing a phase mask exactly in the pupil plane of the imaging system. However, this is not always practical because the complex design of the imaging system leads to a limited practical advantage of this kind of arrangement. In this work, the influence of phase mask position upon wavefront coding technique in the doublet imaging system is studied. The main goal is to find the position where to place the CPM in the imaging system, which type of arrangement can effectively improve the modulation transfer function. Finally, we compare two system configurations, front aperture stop and rear aperture stop in designing the doublet wavefront coded system.

Effects of light intensity on disparity for depth extraction in monochrome CMOS image sensor with offset pixel apertures are investigated. The technology consumes less power, since it does not use external light sources. The offset pixel apertures are integrated in each pixel of the monochrome CMOS image sensor to acquire the disparity for depth extraction. Because the monochrome CMOS image sensor does not contain color filters, the height of the pixel is lower than that of the CMOS image sensor with color filters, resulting in a better disparity. The monochrome CMOS image sensor with offset pixel apertures was designed and fabricated using 0.11 μm CMOS image sensor process. Disparity of the sensor has been measured under various light intensities. The sensor might be useful for three-dimensional imaging in outdoor applications with a simple structure.