Single-photon detector array technologies have advanced significantly in recent years. Cameras now exist that are not only sensitive to single photons but the individual pixels in the sensor provide photon time-of-arrival information the picosecond regime. Such unprecedented sensitivity and temporal resolution opens up a number of exiting new applications, such as light-in-flight imaging, looking around corners with laser echoes, and seeing through dense scattering media. I will discuss the recent developments of the camera technology and discuss our latest results. I will give details of our latest field trials, where we have been using single-photon detector array sensors to see through fog and smoke. I will also discuss our latest results for high-speed imaging in three dimensions. The latest sensor is able to capture 3D data at frame rates greater than 1000 frames per second. This technology is relevant for the analysis of rapidly changing systems where three dimensional information is necessary.

Optically non-line-of-sight sensing or seeing around the corner is a computational imaging approach describing a classical inverse problem where information about a hidden scene has to be reconstructed from a set of indirect measurements. In the last decade, this field has been intensively studied by different groups, using several sensory and reconstruction approaches. We focus on active sensing with two main concepts: The reconstruction of reflective surfaces by back-projection of time-of-flight data and a six degree-of-freedom tracking of a rigid body from intensity images using an analysis-by-synthesis method. In the first case, the inverse problem can be approximately solved by back-projection of the transient data to obtain a geometrical shape of the hidden scene. Using intensity images, only the diffusely reflected blurred intensity distribution and no time information is recorded. This problem can be solved by an analysis-of-synthesis approach.

Hyperspectral imaging sensors acquire images in a large number of spectral bands, unlike traditional electro-optical and infrared sensors which sample only one or few bands. Hyperspectral mosaic sensors acquire an image of all spectral bands in one shot. Using a patterned array of spectral filters they measure different wavelength bands at different pixel locations, but this comes at the cost of a lower spatial resolution, as the sampling per spectral band is lower. Software algorithms can compensate for this loss in spatial sampling in each spectral channel. Here we compare the image quality obtained with spatial bicubic interpolation and two categories of super resolution algorithms: two single frame super resolution algorithms which exploit spectral redundancies in the data and two multiframe super resolution algorithms which exploit spatio-temporal structure. We make a quantitative assessment of the spatial and spectral image reconstruction quality on synthetic data as well as on semi-synthetic mosaic sensor data for applications in security and medical domains. Our results show that multi frame super resolution provides the best spatial and signal-to-noise quality. The single frame super resolution approaches score lower on spatial sharpness but do provide a substantial improvement compared to mere spatial interpolation, while providing in some cases the best spectral quality.

We report on a new platform for separate absorption and multiplication avalanche photodiodes (SAM APDs), developed using 6.1A materials lattice matched to GaSb. Materials and quantum structures grown on GaSb substrates have become of great technological significance for infrared detectors, with absorber options covering the important SWIR, MWIR and LWIR wavebands. The new APD platform is able to exploit these well-established absorber materials, by linking them to a new avalanche multiplication medium, Al0.9Ga0.1As0.08Sb0.92 in a SAM architecture. This opens up the potential for linear and Geiger mode APDs operating across the infrared wavebands for applications such as environmental monitoring, gas sensing and active imaging. In particular, extension of the operating wavelength for active systems with single photon sensitivity, beyond the currently available 1.55µm, is compelling due to the commensurate reduction in solar background photon flux. Recent characterisation has shown that Al0.9Ga0.1As0.08Sb0.92 exhibits desirable avalanche multiplication characteristics. Most notably tunnelling current is negligible due to the material’s large indirect bandgap, while the ionisation coefficients are found to exceed those of other III-V materials. In this work these characteristics are exploited to design and fabricate SAM APDs with breakdown voltages below 15V. This is significantly lower than alternative technologies such as AlInAs/InGaAs APDs, which typically breakdown in excess of 25V in order to limit the magnitude of deleterious tunnelling current. Such a low breakdown voltage is desirable because it greatly aids the design of ROICs enabling future 2D imaging APD and SPAD arrays. In this work Al0.9Ga0.1As0.08Sb0.92/In0.22Ga0.78As0.19Sb0.81 SAM APDs are designed, fabricated and characterised. The detector’s spectral response covers the SWIR window, reaching 2.5µm. Grading between the absorption and multiplication layers is refined to achieve high quantum efficiencies both at room temperature and more challengingly at 77K. Operation below breakdown as a linear mode APD and above breakdown as a Geiger mode SPAD when cooled, are studied and reported. As a further proof of the new SAM APD platform, an Al0.9Ga0.1As0.08Sb0.92/InAs0.91Sb0.09 detectors is also realised, extending responsivity into the MWIR window.

We present the design of a new fast-gated 16 x 16 silicon SPAD array developed in a 0.16 μm BCD technology with builtin 6 ps resolution TDCs (Time-to-Digital Converters), optimized for Non-Line-Of-Sight imaging. The high temporal resolution is achieved by sharing one high-performance TDC among 16 SPADs, without losing spatial resolution, thanks to an identification logic capable of detecting and rejecting collisions. In the SPAD frontend, a low-threshold comparator minimizes temporal jitter, while an active quenching circuit reduces afterpulsing. An event-driven readout scheme optimizes data transfers, however a standard frame-driven photon-counting only mode is also available. The goal is to enable quasi real-time NLOS scene reconstruction by parallelizing the acquisition across multiple spots. Thanks to its high temporal resolution, the detector can be exploited also in other scientific applications, such as clinical diagnostic (with Time-Domain Near Infrared Spectroscopy) and LiDAR (Light Detection and Ranging).

Single Photon Avalanche Diodes (SPADs) provide remarkable features including single-photon sensitivity and picosecond timing capability. For these reasons, they are the detectors of choice in a large variety of applicationsincluding Light Detection and Ranging, Fluorescence Lifetime Imaging, quantum cryptography and many others. In most cases, the electronics used to drive the SPAD plays a crucial role in determining the performance of the overall system. In particular, high speed is still an open challenge for SPAD-based systems. In this paper, we discuss fully integrated electronics and system architectures to maximize the speed of these systems while providing overall high performance both for counting and timing applications.

We present III-Sb resonant cavity-enhanced (RCE) photodetectors suitable for gas detection in the mid-wave infrared. AlAsSb/GaSb DBRs and absorbers of bulk InAsSb or a type-II InAsSb-InAs SLS were grown on GaSb, allowing for operation at 3.72 μm or 4.52 μm, with linewidth Δλ < 50 nm and Δλ < 70 nm, respectively. A barrier diode structure was used, and the absorber thickness was limited to 96 nm for InAsSb – or 192 nm for the SLS – in order to limit the dark currents. High quantum efficiency was obtained through the resonant optical field, while the remainder of the cavity was grown using wide-gap AlAsSb spacer layers not contributing to the dark current. By carefully compensation doping the AlAsSb layers, the 3.72 μm device was bandgap-engineered for a flat Fermi level in the thin absorber, and hence dark currents which scale with the absorber thickness. This can equate to a >20x reduction in noise compared with a conventional nBn detector with full thickness absorber. At 3.72 μm, performance above the BLIP limit imposed on broadband photodetectors was found by calculating for the specific detectivity.

To meet the growing requirement of system integration, it is of great importance and interest to develop ultrathin optical devices with unusual functionalities. As one of the most rapidly expanding frontiers of nanophotonics, optical metasurfaces, or planar metamaterials with subwavelength thickness, have the potential to revolutionize classical optics by displacing refractive optics in many large-scale applications and creating completely new functionalities. Benefiting from the unprecedented capability of metasurfaces in the arbitrary control of light’s amplitude, phase and polarization at subwavelength resolution, optical metasurfaces have provided us new opportunities to fully control the wavefront of light with planar elements and thus realize flat optics based optical devices. In this paper, I am going to highlight our work in dual-polarity metalens, multifunctional metalens, light sword lens, image-switchable holograms, arbitrary polarization manipulation for security, multichannel device for manipulation of twisted light beams and so on. The metasurface have provided unprecedented freedom in engineering the properties of optical waves with the highefficiency light utilization and a minimal footprint for security and defence. The unique properties of these novel metadevices can bring many of the completely new instruments to our daily lives.

Metasurfaces, which are the 2D version of metamaterials, have revolutionised compact optics. Using subwavelength periodic nanostructured dielectrics, the refractive index and absorption properties of metasurfaces can manipulate light to a degree surpassing conventional bulk materials. Using metasurfaces, the phase, polarization, spin (for circularly polarised light), amplitude and wavelength of light can all be arbitrarily tailored to imitate a lens, which we refer to as a metalens (ML). MLs allow a larger choice of materials for optical components and have five major advantages over traditional refractive lenses – superior resolution, miniaturisation, lighter weight, multifunctionality and cost. In recent years, numerous metasurfaces with useful functionalities have been proposed, and although novel in their approach they still have very few real-world applications. One such application is within infrared laser systems, which have real-world use such as laser designators. In this work, we demonstrate polarisation-insensitive metalenses working at λ = 1064 nm, with a d = 1 mm aperture size and four different F-numbers (f# = 0.5 - 5). The lenses are made using amorphous silicon (a-Si) pillars on top of a fused silica substrate, in order to function with a high efficiency (>60%) and little loss – where previous metal-based (plasmonic) metalens devices suffered from low efficiency (<10%) and high loss. The a-Si pillars range from 70-360 nm diameter atop a fused silica substrate, which are fabricated using electron beam lithography (EBL) and reactive ion etching processes. The characterised lenses are shown to have almost diffraction-limited focal spot sizes, agreeing with the theoretical values of λ.f/d, and focussing efficiencies of 60%. Furthermore, we have designed large area lenses with aperture d = 10 mm, where the number of pillars per lens exceeds 550 million. By using an efficient Python script, we are able to make these 100 mm2 samples with just 14 hours of EBL writing time. The 10 mm lenses have focal lengths of 5 mm and 20 mm (F-numbers of 0.5 and 2 respectively). Such large area lenses are of considerable interest to many commercial applications where superior resolution and a light weight are beneficial, including laser designators/targeting, airborne and aerospace applications, as well as handheld devices.

A new solid-state Wavelength-Selective Switch (WSS) based on a Programmable Micro-Diffractive Grating (PMDG) fabricated over a Lithium-Niobate (LiNbO₃) substrate is presented, and its operation described. The device consists of a periodic arrangement of ridge waveguides whose optical phase delay can be individually or collectively tuned through the electro-optics (Pockels) effect. Each waveguide is patterned with a metal electrode and connected to an external microprocessor-based driving unit. By appropriately programming the phase shift induced on each waveguide, the far-field diffraction pattern of the grating can be shaped in order to implement complex all-optical signal processing functions, such as 1-to-M demultiplexing, beam splitting, beam steering or wavelength-selective filtering. Once integrated within a telecommunications infrastructure, this component can clearly enhance the level of flexibility and robustness of the network optical physical layer.

In the modern world there is a pronounced tendency for miniaturization. It applies to navigation systems and sensors used in them. Due to this, micromechanical gyroscopes in particular, became widespread, which made it possible to measure the angular velocity of miniature objects. But their sensitivity to accelerations and vibrations limits the range of their application. Currently, research in the direction of minimizing the size of general and precise optical gyroscopes is relevant, i.e. the development of micro-optical gyros. The most promising type of micro-optical gyro is a resonator one. Wherein the principle of operation of all prototype resonator micro-optical gyroscopes developed to date involves the scanning of a passive ring resonator in frequency. This work is devoted to a new approach to the construction and principle of operation of a resonator micro-optical gyroscope. This approach does not require scanning the passive ring resonator in frequency and is achieved through the use of a Mach-Zehnder modulator, one of whose arms is connected to a passive ring resonator. This allows to simplify the design of a micro-optical gyroscope, to obtain a mutual configuration, and to drop the tunable laser (required in most schemes) in favor of a laser with a constant generation frequency. The paper also discusses the limitations of the new approach and ways to overcome them.

In the context of decreasing human engagement in conflicts and ever wider areas of responsibility, vision-based Unattended Ground Sensor (UGS) deployment is mandatory for wide and long range situational awareness while relieving and protecting human resources in safe areas. High-resolution single sensor concepts imply processing a huge amount of pixels either off-board, by a high bandwidth communication media to a central processing infrastructure, or on-board with a powerful embedded processor. Nevertheless, these approaches decrease EM stealth and require a lot of electrical power affecting the sensor autonomy. To allow on-board real-time processing while optimizing Size,Weight and Power (SWaP) requirements, this paper presents a bi-focal vision UGS concept. It couples 4 low-resolution CMOS sensors with small, light and high aperture optics for providing the equivalent of a 17 Mega Pixels single-sensor with 130^◦ FOV.

Compressed Sensing provides an innovative imaging technique with fundamental differences to conventional imaging. A collection of low-resolution measurements is taken to reconstruct a picture with higher resolution computationally. The significant advantage is the small number of measurements and reduced number of measured pixels compared to the number of pixels in the reconstructed picture. This can be achieved because of sparsity. A realization of this concept is the single-pixel-camera, which uses a single-pixel-detector to measure only the brightness of the target scene after modulation with a digital micromirror device. Obviously, the patterns used for the modulation must satisfy certain properties. For example, the coherence of the measurement matrix containing those patterns is related to the performance of the camera. It seems efficient to construct matrices with optimal coherence or other performance parameters. Other approaches use specialized matrices depending on specific applications. This paper discusses the relation between the mathematical properties such as coherence and other parameters and the practical results from exemplary tests. Therefore matrices from different approaches are implemented and combined with a primal-dual-algorithm.

Hyperspectral imaging involves the sensing of a large amount of spatial information across several adjacent wavelengths. Typically, hyperspectral images can be represented by a three-dimensional data cube. The collected data cube is extremely large to be transmitted from the satellite/airborne platform to the ground station. Compressive sensing (CS) is an emerging technique that acquire directly the compressed signal instead of acquiring the full data set. This reduces the amount of data that needs to be measured, transmitted and stored in first place. In this paper, a comparison of a CS method implementation for an ARM and for a GPU is conducted. This study takes into account the accuracy, the performance, and the power consumption for both implementations. The 256-cores GPU of a Jetson TX2 board, the dual-core ARM Cortex-A9 of a ZYNQ-7000 SoC FPGA and the quad-core ARM Cortex-A53 of a ZYNQ UltraScale SoC FPGA are the target platforms used for experimental validation. The obtained results indicate that the embedded GPU is faster but uses more power. Therefore, the most appropriate platform depends on the performance and power constraints of the project.

In this paper we proposed a new iterative process of sorting an array of signals, which differs from the known structures of sorting signals by uniformity, versatility, which allows direct and inverse sorting of an array of analog or digital signals. We proposed the structure of the processor based on the node that sorts the array of processed signals. Let us show the variety of the sorting node, which can be executed both iterative and pipeline–type, implementation of homogeneous sorting structure, consisting of two layers of base cells and a multichannel sampling and holding device and show that for a large number of operations and functions performed on image processing and filtering, it is necessary to sort by the signal level in the selected image window. The base cells consist of no more than 20 CMOS 1.5μm transistors, the total power consumption of the sorting node on 10 continuously logical base cells (CL BC) is 2mW, the supply voltage is 1.8÷3.3V, the range of an input photocurrent is 0.1÷24μA, the conversion cycle is 10μs. The paper considers results of design and modeling of CL BC based on current mirrors (CM) for creating picture type image processors (IP) with matrix parallel inputs-outputs. Such sorting nodes based on them have a number of advantages: high speed and reliability, simplicity, small power consumption, high integration level. The inclusion of an iterative node for sorting signals into a modified nonlinear IP structure makes it possible to significantly simplify its design and increase the functional capabilities of such processor. We evaluated the technical parameters of such a relational preprocessor. The simulation results confirm the proposed approaches to the design of sorting nodes of analog signals of the iterative type, which simplify the complexity of the nodes by an order of magnitude, ensuring their uniformity, regularity and simplicity of scaling. The power consumption of the processors does not exceed 2mW, the response and processing times are 10μs and can be less by an order of magnitude, the supply voltage is 1.8÷3.3V, and the operating currents are optimally in the range of 10÷20μA. The energy efficiency of the proposed preprocessor with the iterative sorting node is 25x10⁹ op / s • W, which corresponds to the best technical solutions. In the work we are shown, that after sorting or comparative analysis of signals by levels of selected window of image, a promising opportunity appears to implement image processors with enhanced functionality using the new method of weighting-selecting rank differences of signals. The essence of the method is that by composing the differences of the signals ordered by rank and the upper level of their range, we can simultaneously form several resulting output signals, choosing the necessary difference signals from their set according to the control commands and weighing them additionally before the summation. We are shown that using this approach and the method of processing the current window signals significantly expands the set of operations and functions for filtering images, simplifying hardware implementation of IP, especially for analog and mixed technologies. We determined the set of executed command functions by such a processor based on the sorting node, show how it can be used to separate the rank from the array of signals and analyze the new approach for the programmable selection of the required rank or the difference between the signal ranks. The use of difference-rank decomposition allows to significantly expanding the transformations range, performed over the signals of the current fragment of the processed image. We determined set of basic possible executable instruction-functions by processors based on such a proposed method, presenting the simulation results in Mathcad, PSpice OrCad and other environments. We discussed the comparative evaluation of various modifications and options for implementing processor. We analyzed the new approach for the programmable choice of its function or set of functions, including the choice of the required differences between the ranks of signals and their weights. We show the results of design and modeling the proposed new FPGA-implementations of MIP. Simulation results show that processing time in such circuits does not exceed 25 nanoseconds. Circuits are simple, have low supply voltage (2.5 V), low power consumption (50mW), digital accuracy. Calculations show that when using an Altera FPGA chip EP3C16F484 Cyclone III family, it is possible to implement MIP with register memory for image size of 64*64 and window 3*3 in the one chip. For the chip for 2.5V and clock frequency 200MHz the power consumption will be at the level of 200mW, and the calculation time for pixel of filters will be at the level of 25ns.

In this paper, we proposed a new iterative process of sorting an array of signals, which differs from the known structures of sorting signals by uniformity, versatility, which allows direct and inverse sorting of an array of analog or digital signals. The basic elements of the proposed sorting structures are simple relational nodes. Such elements can be implemented on a different element basis, including, on devices for selecting a maximum or minimum of two analog or digital signals, which are implemented on CMOS current mirrors and carry out the limited difference function of continuous logic. We offered implementation of homogeneous sorting structure on such elements, consisting of two layers and a multichannel sampling and holding device. Nine signals corresponding to a selection window of a matrix sensor are fed to this structure, we sort them in five iterative steps, and at the output we receive the signals sorted by the rank, which, using the code controlled programmable multiplexer, generates an output signal, corresponding to the selected rank. We evaluated the technical parameters of such a relational preprocessor. The base cells consist of no more than 20 CMOS 1.5μm transistors, the total power consumption of the sorting node on 10 continuously logical base cells (CL BC) is 2mW, the supply voltage is 1.8÷3.3V, the range of an input photocurrent is 0.1÷24μA, the conversion cycle is 10μs. The paper considers results of design and modeling of CL BC based on current mirrors (CM) for creating picture type image processors (IP) with matrix parallel inputs-outputs. Such sorting nodes based on them have a number of advantages: high speed and reliability, simplicity, small power consumption, high integration level. The inclusion of an iterative node for sorting signals into a modified nonlinear IP structure makes it possible to significantly simplify its design and increase the functional capabilities of such processor. The simulation results confirm the proposed approaches to the design of sorting nodes of analog signals of the iterative type, which simplify the complexity of the nodes by an order of magnitude, ensuring their uniformity, regularity and simplicity of scaling. The power consumption of the processors does not exceed 2mW, the response and processing times are 10μs and can be less by an order of magnitude, the supply voltage is 1.8÷3.3V, and the operating currents are optimally in the range of 10÷20μA. The energy efficiency of the proposed preprocessor with the iterative sorting node is 25x10⁹ op / s•W, which corresponds to the best technical solutions. In the work we are shown, that after sorting or comparative analysis of signals by levels of selected window of image, a promising opportunity appears to implement image processors with enhanced functionality using the new method of weighting-selecting rank differences of signals. The essence of the method is that by composing the differences of the signals ordered by rank and the upper level of their range, we can simultaneously form several resulting output signals, choosing the necessary difference signals from their set according to the control commands and weighing them additionally before the summation. We are shown that using this approach and the method of processing the current window signals significantly expands the set of operations and functions for filtering images, simplifying hardware implementation of IP, especially for analog and mixed technologies. We determined set of basic possible executable instruction-functions by processors based on such a proposed method, presenting the simulation results in Mathcad, PSpice OrCad and other environments. We discussed the comparative evaluation of various modifications and options for implementing processor. We analyzed the new approach for the programmable choice of its function or set of functions, including the choice of the required differences between the ranks of signals and their weights. We show the results of design and modeling the proposed new FPGA-implementations of MIP. Simulation results show that processing time in such circuits does not exceed 25 nanoseconds. Circuits are simple, have low supply voltage (2.5 V), low power consumption (50mW), digital accuracy. Calculations show that when using an Altera FPGA chip EP3C16F484 Cyclone III family, it is possible to implement MIP with register memory for image size of 64*64 and window 3*3 in the one chip. For the chip for 2.5V and clock frequency 200MHz the power consumption will be at the level of 200mW, and the calculation time for pixel of filters will be at the level of 25ns.

The results of application possibility research of the optimized body form with the minimal force of aerodynamic resistance as a heat sink in a convective gas flow are presented in the paper. The computational experiment was carried out in the Ansys Fluent software system. The conditions of comparison of heat-conducting bodies in the computational experiment are the preservation of constants: the volume and shape of the working area; distances from sources, drains and centers of bodies; gas flow rates; body mass; thermal power source and other secondary characteristics in addition to just the very shape of the surface. The main advantage of the resulting optimized body shape is that it coincides with the streamlines, thereby not separating flow from the surface around it. Thus, the entire surface area will be the effective surface area of the heat sink, unlike other compared forms of bodies, due to which the temperature of the heat-loaded element placed in the center of the heat sink will decrease.

The creation of effective procedures for the design and fabrication of RF MEMS switches with specified electrophysical properties for operation in different frequency ranges is an urgent task. This is due to the widespread use of RF MEMS in various fields of microelectronics. The task is complicated by the fact that, based on the areas of application, different variants of technologies, materials, topological and structural solutions are used to create RF MEMS switches. The article proposes a method of design and fabrication of RF MEMS switch with specified properties based on creating a model of micromechanical switch, taking into account significant technological parameters, properties of materials and options for structural and topological solutions. For the selected three groups of factors, the analysis of the main characteristics and parameters affecting the electrophysical and frequency properties of RF MEMS switch is carried out. The analysis of technological processes of fabrication allowed determining the influence of the non-etched photoresist layer on such electrophysical characteristics as the capacity of the switch in the up- and down-state. The analysis of the properties of materials, the influence of thickness changes in the formation of the dielectric layer and membrane, as well as the thickness of the gap between the membrane and the dielectric layer on the electrophysical and frequency properties of RF MEMS switch. It is established that the most significant parameters affecting the formation of the frequency characteristics of the switch is the change in its geometric dimensions. The developed model RF-MEMS switch, which takes into account the interaction highlighted important properties and relations with the electrical and frequency characteristics of RF MEMS switch. Modeling and analysis of the following characteristics (consequences of the model) RF MEMS switch.

The 2D electromagnetic modeling distribution of electric fields for stationary and non-stationary scattering process in the time domain mode was developed. The distributing system of the optical type was expressed. Given system allows to form 5-beam directional pattern (DP) for receiving active phased antenna radar (APAR).

At reduction of the sizes of the distributing system, distance between its output reduce in once, in contrast with distance between radiators APAR. In such event corner deflections of the ray in DP APAR will corner of the deflection less in distributing system in n once also. For considered systems reduction factor of the geometric sizes n has formed the order 7. In corresponding to number once and was increased a corner of the deflection of the ray α in distributing system.