This PDF file contains the front matter associated with SPIE Proceedings Volume 11868, including the Title Page, Copyright information, and Table of Contents

Optronic systems for the defence market are available from the UV to the LWIR wavelengths but the ideal band very much depends on the particular application and their environment. This lecture will cover some of the more important features of each type of optronic sensor and using examples from the experience gained over many years of system development by Tecnobit for Airborne, Navel and Land sectors, suggests some broad recommendations.

The principles behind up-conversion time correlated single photon counting (TCSPC) lidar are presented. This technique can easily extend the detection range of conventional SPADs to reach into the MIR by utilising nonlinear processes to up-convert the wavelength of the MIR to the visible or NIR. The up-converted light can then be detected by a standard Si-SPAD. This allows for high resolution and sensitivity to be achieved while operating the system at room temperature. The technique is demonstrated through a short-range lidar system measuring off diffusely reflecting targets. The system was operating at 3 μm with pulse energies around 3 nJ and a pulse width of 300 fs. The up-conversion was performed inside a PPRKTP crystal placed within a Nd:YVO₄ laser cavity operating at 1064 nm, which generated pulses at 790 nm. The temporal FWHM of the lidar response was 76 ps, and the system showed sub-mm range accuracy, demonstrated by scanning 3D targets.

Single photon-counting avalanche photo-diode (SPAD) can measure the photon flux from uncorrelated single photons. In present work, we show how the sensor photon count rate is related to the intensity or the radiant flux that is reflected from surfaces in the sensor's field of view and incident on the sensor array. After a brief theoretical discussion of photon flux imaging, we examine various de-noising strategies and the effect of motion blur. Finally, we present the application of a fast super-resolution neural network (FSRCNN) to scale image by a scaling factor of 3× to obtain super-resolution images (32 × 32 → 96 × 96).

We show a novel architecture for massively parallel FMCW LiDAR based on multiheterodyne mixing of two triangular chirped soliton microcombs generated in integrated Si3N4 microresonators using a single laser source and a single coherent receiver. We demonstrate a proof of concept experiment with 5.6 MPix/s acquisition rates.

Conventional optical ranging techniques require timing modulated light sources to provide for the time-of-flight information, which may allow for detection, jamming or decoy by a third-party with information to the modulation pattern. Quantum ranging techniques, or quantum lidar, use spontaneous parametric down converted light sources to provide the timing correlation, where entanglement is not necessarily exploited in the simplementation, and is complex and expensive. Here we propose the use of stationary broadband light generated from a laser diode operating below threshold to provide the timing correlation, as extracted from thermal photon bunching.

Timing measurements with single photon detectors have acquired a prominent role in many applications, especially where they allow the recovery of faint light signals in harsh environments. We present a new fully-integrated multifunctional Time-to-Amplitude Converter (TAC), featuring 8 channels with a full scale range up to 100ns and a linearity better than 1% of the LSB peak to peak. The maximum speed of the converter is obtained in the Fast-TAC configuration (80MHz), while the precision of the converter can be maximized by exploiting multiple channels to perform the same conversion, achieving an overall jitter as low as 1.4ps.

The identification and localization of laser threats in a free-space channel is an increasingly important capability as active laser sensors become more widely used in civilian and military applications. Early identification of a laser source requires o-axis detection of laser light scattered out of the optical channel by molecules and aerosols in the free-space channel. In this work we report on the development of a sensor system for the o-axis detection of scattered laser light from a non-cooperative laser source. An image processing approach to the detection and localization of a laser in a scene is presented. The performance of the sensor system is quantified with experiments performed inside the laboratory and in realistic daylight background conditions.

The inherent differences of the Compressed Sensing (CS) imaging technique result in advantages compared to conventional imaging for scenes containing a rather low amount of relevant data. Such information “sparsity” enables the reconstruction of images with a small number of low-resolution measurements, focusing on the relevant information already during the measurement process. The crucial “sparsity” requirement of the CS framework is fulfilled in certain threat detection applications like e.g. solar blind UV missile warning. To assess, whether CS technology is applicable for threat detection, where short acquisition times and robust and reliable detection are a must, we developed a universal framework for the assessment of the performance of compressed sensing algorithms. This framework includes the most promising algorithms from our past performance assessments and a selection of image quality metrics suited for conceivable applications. The currently implemented algorithms are TVAL3, NESTA, FPC and L1-primal-dual algorithms. Because of the structure of the realized framework, the integration of further algorithms and metrics as well as alternative image acquisition approaches is possible. The studied data sets include scenes were the approach of a threat is modelled for our single-pixel-camera setup as well as recordings done with solar blind UV- and IR-imagers that were broken down to single-pixel-measurements of varying compression.

We demonstrate a hybrid photonic integrated laser that exhibits an intrinsic linewidth of 40 Hz, while offering unsurpassed megahertz actuation bandwidth with the tuning range larger than 1 GHz, attained by a DFB laser self-injection locking to a high-Q Si3N4 microresonator with AlN piezoelectrical actuator, allowing both single-line operation and microcomb generation. We develop a compact FMCW LiDAR engine with triangular chirp optical signals at a rate up to 1 MHz, without requiring any linearisation.

Spectral imaging allows data acquisition at any particular frequency range in the electromagnetic (EM) spectrum to extract additional information. The light energy emitted from the sources or reflected by the objects is selectively sensed in specific bands of the EM spectrum to produce images. Multispectral imaging in long-wave infrared (thermal wavelengths) is an emerging research area due to its ability to identify objects precisely from the emission spectrum for chemical detection, gas sensing, night vision, and surveillance applications.1 The multispectral imaging in the long-wave infrared is limited by the conventional filter technologies and limited materials responding in the thermal wavelengths. Wavelength filters based on surface plasmon resonance can overcome such limitations and can produce filters using a single nanoscale thick metal film with wide wavelength tunability. This paper presents a wavelength filter technology operating in six bands of the thermal region (7 – 14 μm). With copper (Cu) as the metal layer and germanium (Ge) as the cap layer, the transmission efficiency of lithographically patterned multilayer plasmonic filters on gallium arsenide (GaAs) substrate has improved up to 60% in thermal wavelengths. Thus, a thermal multispectral filter system is realized to acquire narrow transmission bands in the thermal region using surface infrared plasmonics of Cu in a dielectric-metal-dielectric (DMD) mosaic of GaAs-Cu-Ge. The filters are then integrated on thermal image sensors mounted on an in-house processing electronic platform to develop a six-band multispectral thermal sensor system. The working of the snapshot thermal multispectral sensor system is demonstrated by capturing the images at six different bands. The developed multispectral system can be adopted for non-destructive thermal imaging or can be used directly as a microspectrometer for various thermal spectroscopy applications

Quartz-enhanced photoacoustic spectroscopy (QEPAS) [1] is one of the most efficient ways to obtain sensitive, selective, robust gas sensors. The main drawback of QEPAS comes from usage of quartz tuning fork (QTF) as a mechanical transducer. QTF is not specifically design for photoacoustic gas sensing and its further integration is limited. As a solution we propose a silicone resonant MEMS based on capacitive transduction mechanism. This sensor, specifically designed for acoustic sensing purposes, can be an efficient transducer for sound wave detection able to advantageously replace a QTF. Capacitive transduction allows reaching high sensitivity of the sensor while choice of silicon is favorable in design flexibility, fabrication maturity, stability and further integration with CMOS electronics. We have developed and fabricated various resonator designs on silicon. Specific designs were created to sensor voltage output using an analytic model developed by our group [2]. Photoacoustic measurement was performed on calibrated mixtures of methane using commercial Eblana distributed feedback laser laser emitting at 1.63 μm. We achieved a reproducible limit of detection on methane: 1000ppmv in 5s for 2f detection and 700ppm in 5s for 1f detection (figure 1) (resonator resonance frequency 22.65 kHz and Q-factor of 250). Then, we compared the experimental results with standard QTF in off-beam configuration for which the limit of detection: 30ppmv in 5s for 2f detection and 25 ppm in 5s for 1f detection. Thus, the difference of detection limit between QTF and MEMS amounts factor 28 for 1f detection and 33 for 2f detection. [1] Kosterev, A. A., Bakhirkin, Y. A., Curl, R. F., & Tittel, F. K. (2002). Quartz-enhanced photoacoustic spectroscopy. Optics letters, 27(21), 1902-1904. [2] Trzpil, Wioletta, et al. "Analytic Optimization of Cantilevers for Photoacoustic Gas Sensor with Capacitive Transduction." Sensors 21.4 (2021): 1489.

Free-Space Optical (FSO) communication is a technology that enables ultra-high-rate data exchange and will be crucial in enabling secure Quantum Key Distribution (QKD) over long distances. However, FSO communication systems are comparatively complex technologies, comprising a variety of subsystems that all have to work together in a coordinated way. Hence, assessing the feasibility of establishing a (classical or quantum) link in a given communication scenario is a difficult task in itself. Here we introduce QCalc, a software tool that aims at easing and streamlining this process, allowing the user to keep track of all the relevant parameters in a link budget. This software computes the total transmissivity, and thus, the signal intensity observed at the receiver for any given parameters of the transceivers and the FSO communication channel. The estimated signal intensity can then be used to compute either the link budget in a classical communication scenario or the secure key rate of a QKD protocol.

Quantum technologies containing key GaN laser components will enable a new generation of precision sensors, optical atomic clocks and secure communication systems for many applications such as next generation navigation, gravity mapping and timing since the AlGaInN material system allows for laser diodes to be fabricated over a wide range of wavelengths from the U.V. to the visible. We report our latest results on a range of AlGaInN diode-lasers targeted to meet the linewidth, wavelength and power requirements suitable for quantum sensors such as optical clocks and cold-atom interferometry systems. This includes the [5s²S_1/2-5p²P_1/2] cooling transition in strontium⁺ ion optical clocks at 422 nm, the [5s^{2 1}S₀-5p₁P¹] cooling transition in neutral strontium clocks at 461 nm and the [5s²s_1/2 – 6p²P_3/2] transition in rubidium at 420 nm. Several approaches are taken to achieve the required linewidth, wavelength and power, including an extended cavity laser diode (ECLD) system and an on-chip grating, distributed feedback (DFB) GaN laser diode.

The Trojan-horse attacks on quantum key distribution (QKD) systems are known to be a threat to secure key sharing between two parties (Alice and Bob). To protect a QKD system against such attacks a variety of passive optical and active optical devices embedded in Alice’s and Bob’s setup are widely used. However, a security analysis against the Trojan-horse attack is required to ensure the unconditional security of a QKD system. We present a security analysis against the Trojan-horse attacks on a practical fiber-based QKD phase-coding system in 400–1700 nm spectral range. The obtained results made it possible to calculate the higher limit of average photon number returned to Eve and the probabilities of Eve’s success of the attack on a particular QKD system.

Harnessing quantum randomness for the generation of random numbers is an important concept crucial for information security and many other computer-related applications. Quantum random number generators (QRNGs) are evolving from bulky, slow, and expensive implementations towards chip-sized devices. Since computers are deterministic devices, and as such incapable of generating randomness, the prevailing modus operandi is that a QRNG is added to a computer, realizing what is known as "probabilistic Turing machine". State-of-the-art QRNGs use different hardware ports (USB, PCIe,...) and manufacturer-specific bit-transfer protocols, which limits their use by both hardware and software developers. In this work we propose an entirely different approach to use of randomness in a general digital environment (computers included), via a new, dedicated logic circuit: the random flip-flop (RFF), which is fully inter-operable with the standard logic circuits and can form an integral part of microprocessors, ultimately as an instruction-set extension. RFFs can be regarded as the missing link that closes the full set of logic elements; we show their use in digital and analog applications. We also build an RFF on a silicon chip using CMOS process. That, in principle, allows having any number of RFFs on a particular chip (e.g. microprocessor, FPGA, ASIC, ...), enabling both a very fast and massively parallel random number generation. Applications are endless, including recent trends in artificial intelligence, biomimetic stochastic computer and graphics processors. Integrated RFF does not need hardware ports nor bit-transfer protocols and allows an easy integration of randomness into higher programming languages.

Additive manufacturing – specifically 3D laser lithography – has become a powerful technology for the fabrication of 3D objects with sub-micrometric resolution. This technique has already been applied in a broad range of fields, including metamaterials, biomedicine, and optics. However, there is a growing interest in the incorporation of new features or functionalities in the printed structures that can open up new opportunities in the field.1,2 The lecture will present our latest advances in the design of functional polymer based photoresists for 3D laser lithography. In particular, a new class of on-demand cleavable materials will be introduced that can be removed after being printed (subtractive manufacturing).3 Futhermore, new photoresists based on stimuli-responsive materials for the preparation of dynamic and programable microstructures will be presented. We believe that these new materials will have significant impact on future applications, where the advantages of high resolution additive and response on-demand can be combined. [1] C. A. Spiegel, M. Hippler, A. Münschinger, M. Bastmeyer, C. Barner-Kowollik, M. Wegener, E. Blasco. Adv Funct Mater, 2020, 30, 1907615. [2] C. Barner-Kowollik, M. Bastmeyer, E. Blasco, G. Delaittre, P. Mueller, B. Richter, M. Wegener. Angew Chem Int Ed, 56, 15828 (2017). [3] R. Batchelor, T. Messer, M. Hippler, M. Wegener, C. Barner-Kowollik, E. Blasco. Adv Mater, 31, 1904085 (2019).

State-of-the-art personnel screening systems reconstruct images by using multiple-input-multiple-output (MIMO) radars, which require a large number of transmit and receive channels along a two-dimensional array. We propose a novel concept for security screening which does not require the person to stand still and only employs a one- dimensional array: Our approach is built on the use of inverse synthetic aperture radar (ISAR) imaging based on a vertical line array. This means that the moving person inversely samples a synthetic aperture along the horizontal dimension. In order to reconstruct an image by the ISAR principle, the test subject's velocity relative to the radar aperture needs to be known. Therefore, we employ an additional radar module which measures the person's velocity, assuming that the person is moving parallel to the aperture plane. Experiments with a mannequin carrying threat objects were performed. The mannequin was moved on a traversing rail with 1 m/s and its velocity was estimated by a commercial radar module emitting a chirp sequence signal. The estimation was in very good accordance with the rail's real moving speed. With the determined target velocity an image was reconstructed along the horizontal direction by the ISAR principle. Along the vertical direction, the focusing was performed using a MIMO line array of 45 transmitter and 24 receiver channels with a total height of 60 cm. That way, and by employing broadband signals (70 GHz - 80 GHz), three-dimensional high-resolution images were obtainable. Promising results were obtained from the measurements and different threat objects were made visible.

In the present work, we report on resolution enhancement of a terahertz imaging system using the terajet effect. A wavelength-scaled particle (a Te on cube for simplicity) was used to localize incident radiation to a subwavelength volume and focus it directly onto the objects under imaging. A strained-silicon modulation field effect transistor was used as a direct detector of an incident terahertz beam at 0.3 THz. At first, the terahertz imaging of the objects was performed without the cube. A clear enhancement of the resolution of the terahertz image was obtained when the cube was placed in the focal point of the terahertz beam in front of the object of interest.

The physical security of government buildings, banks, schools, higher education institutions, train stations, airports and lastly but not least the people within them has been the key for the sustainability of our society. Day after day, technologies have been invented to improve the physical security of buildings. In this paper a Thru-Vision passive imager having a centre frequency of 250 GHz and a bandwidth of 36 GHz was used to scan images and detect different types of hidden objects under clothing. The clothing materials used in the experimental images were made of cotton, wool and leather. Experimental images show that millimetre-wave (MMW) radiations over the band (232-268) GHz can penetrate these materials and detect hidden objects. Experimental results indicate that the transmission over the MMW band is dependent on the clothing material, thickness and moisture content. The images obtained from the Thru-Vision passive imager provide information about the shape, the size and the dimensions of the hidden objects. These objects were a metal plate and a wax plate. Experimental images show that spraying water on textiles increases the loss over the MMW band and makes the objects less visible, but at the same time they remain detectable. Furthermore, the experimental measurements indicate that textiles made of cotton and wool have higher transmissions of MMW radiation and enabling more reliable object detection compared with leather. These findings indicate the potential of the MMW band of the electromagnetic spectrum for offering a non-contact method of screening people, a touchless pat-down security search for use in scenarios where harmful viruses and bacteria may prevail. This capability will increase the detection probabilities and reduce the false positives rates in security screening.

Passive millimeter-wave imaging has been demonstrated to detect a wide variety of hidden objects. Polarimetric imaging can obtain much more information about observing scenes. Some works have reported polarimetric imaging simulations and multiple linear polarization imaging experiments. However, there is no work reporting the independently circular polarization imaging experiments of indoor body security inspection scenes. In this paper, we have constructed an imaging system, which can generate circular polarization images. The imaging system mainly contains two circular polarization antennas, a W-band radiometer, a focal plane lens, an arcshaped orbit for horizontal pixel, a plane reflector for vertical pixel, and a control computer. The radiometer is placed on the base of the arc-shaped orbit. By putting a left-hand or right-hand circularly polarized antenna on the flange of the radiometer, we can acquire the corresponding left-hand or right-hand circular polarization image. Circular polarization imaging experiments of several human security screening scenarios have been conducted and polarization characteristics have been analyzed. The experimental results indicate that circular polarization imaging can obtain different information from linear polarization imaging and can be helpful to improve image quality.

Prospects for the development of devices for visualizing terahertz (THz) radiation sources can be associated with the use of the results of old studies (1965–1978) on the absorption of THz radiation by metal nanoparticles. This “renaissance” demonstrates that metallic nanoparticles can be used as nanotransducers of invisible THz radiation to infrared (IR) radiation detectable by a commercial IR camera. The investigated THz-to-IR converters are matrices that are transparent both in the THz radiation range to be visualized and in the operating range of the IR camera; matrices contain embedded metal nanoparticles. The latter, when irradiated with THz rays, convert the energy of THz photons into heat and become nanosources of IR radiation for the IR camera. In metal nanoparticles, the mechanisms of absorption of THz radiation and its conversion into heat are realized through dissipation of the energy of THz photons due to multiple scattering of electrons, as well as because of excitation of two types of phonons (transverse and longitudinal ones). The conversion of THz energy into the energy of transverse phonons occurs directly, while dissipation and excitation of longitudinal phonons occurs indirectly, through the excitation of Fermi electrons. Polyvinylchloride (PVC) was chosen as the matrix material, and gold nanoparticles were chosen as nanoparticles-fillers.

We reported electrochemiluminescence (ECL) in which light is emitted from the excited state of a redox-active material generated by electrochemical reactions. We applied AC driven system to enable quick emission response and high emission intensity. In this paper, we report that electrochemically triggered upconverted emission through triplet–triplet energy transfer (TTET) and subsequent triplet–triplet annihilation upconversion (TTA-UC) is observed for the first time in the electrochemiluminescence properties of a Ru complex/diphenylantracene (DPA) containing electrochemical cell.

A unique photocurrent response of a photovoltaic cell using photosynthetic protein bacteriorhodopsin (bR) is similar to that seen in the retinal ganglion cell, therefore, there are considerable interest in utilizing bR in visual sensors. A position sensitive detector (PSD) is a monolithic photosensor utilizing photodiode surface resistance. When a spot light strikes the PSD, an electric charge proportional to the light intensity is generated at the incident position. This electric charge is driven through the resistive layer and collected by two electrodes as photocurrents, while being divided in inverse proportion to the distance between the incident position and each electrode. In this study, we present 1D 10-cm-long PSD based on bR instead of organic semiconducting polymers. A bR-PSD consists of a dip-coated bR film on a high-resistivity indium-tin-oxide (ITO)-PET film, and counter ITO-PET. The position sensitive output signals of the PSD are measured in response to the intensity-modulated light of a green laser. Nonlinearity, δ=2×RMS deviation/full scale, is a measure of the distortion of the sensor output. An acceptable device has nonlinearities of less than 15%. When the position was detected at a beam diameter of φ = 5 mm, 40 mW/cm2, and the measurement interval 1 mm, the nonlinearity was 3.42%. Especially within an area of position detection error of less than 1%, the nonlinearity was 0.33%. When a beam diameter of φ = 1.5 mm and a measurement interval 500 μm, the nonlinearity showed 0.81% within the range of the light receiving centre of 2 cm. It satisfies 15%, which is the allowable range of general nonlinearity. The bR-PSD showed excellent linearity for all increments measured. Notably, the low cost (3 Euro) and simplicity of fabricating bR-PSD, and no requirement for a bias supply are two of the major advantages over conventional semiconductor material.

New chalcogenide glass (FI-02) has been developed successfully, with its most effective feature being its infrared (IR) transmittance. FI-02 can transmit up to 20-μm wavelengths of IR light and has a very wide transmittance spectrum in the IR region as compared to the germanium single crystal and conventional chalcogenide glass. Its excellent transmission property is expected to improve the brightness and clarity of IR images. In addition, FI-02 has a high refractive index of 3.47 (at a wavelength of 10 μm). This is the highest refractive index among glass materials, thus enabling the fabrication of thin and high-performance IR lenses. Furthermore, unlike crystal materials, FI-02 can be processed through press molding. This enables to make high performance lens with high productivity. To investigate the performance of FI-02 as an IR lens material, we made two types of IR lens units: focal length (FL) 10.5 mm (standard type) and FL 2.04 mm (super wide-angle type). In the standard lens unit, IR images were captured with better contrast as compared to those captured using the germanium or conventional chalcogenide glass lenses. This could be attributed to the good IR transmission property of FI-02. In the super wide-angle type, IR images were captured that were wider and less distorted as compared to those of the typical wide-angle IR lens unit. This was attributed to the advantage of the high refractive index of FI-02 and its ability to form aspherical shapes through press molding.

The paper discusses the development and application of nanostructured surface systems for a wide range of applications. By programming the parameters of the CAA-PVD (Controled Accelerated Arc-PVD) Deposition process, it becomes possible to effectively control the performance properties of surface modifying systems and products with such systems. Modification of the surface properties of products such as cutting tools, friction pairs and medical implants provides an optimal combination of properties such as surface hardness and plasticity, high adhesion to the substrate and low adhesion to the counterbody material. The strict determinism of the process parameters allows it to be included in the automatic control system of modern manufacturing with significant energy savings and a high level of environmental safety.

A new method for determining surface roughness based on improving the kinematics of the milling cutter movement during micro-cutting has the advantage of the precise spatial position of the micro cutter edge. A change in the components of the speed of movement and rotation during a complex movement of the cutter changes the mechanism of plunging of the cutting edge into the workpiece material. Based on the model developed in this work, the kinematic parameters of the cutter were determined, and new relationships between the cutter geometry and parameters of the technological process were discovered. The revealed new relationships made it possible to determine not only the mechanism of chip formation but also the dimensions of damages to the workpiece surface during plunger cutting.

In this work, a new mathematical model for determining the mechanism of plunging the cutting edge of end mills with a stable passage of the cutting into the workpiece material has been developed. The new mathematical model describes the chip width as a function of the feed rate, the number of teeth and the cutter diameter. The present work shows that the theoretical value of the width of the cut layer can be used as a key parameter controlling the cutting force and as a key factor determining the plunging mechanism. A comparison of model results with experimental data has shown that modeled and experimental heights of microroughness in the stable cutting sections are in agreement within 0.05 μm that indicates the high accuracy of the developed mathematical model.