Photo-Responsivity Improvement of Photo-Mobile Polymers Actuators Based on a Novel LCs/Azobenzene Copolymer and ZnO Nanoparticles Network

The efficiency of photomobile polymers (PMP) in the conversion of light into mechanical work plays a fundamental role in achieving cutting-edge innovation in the development of novel applications ranging from energy harvesting to sensor approaches. Because of their photochromic properties, azobenzene monomers have been shown to be an efficient material for the preparation of PMPs with appropriate photoresponsivity. Upon integration of the azobenzene molecules as moieties into a polymer, they act as an engine, allowing fast movements of up to 50 Hz. In this work we show a promising approach for integrating ZnO nanoparticles into a liquid crystalline polymer network. The addition of such nanoparticles allows the trapping of incoming light, which acts as diffusive points in the polymer matrix. We characterized the achieved nanocomposite material in terms of thermomechanical and optical properties and finally demonstrated that the doped PMP was better performing that the undoped PMP film.

A survey on rendering homogeneous participating media

Participating media are frequent in real-world scenes, whether they contain milk, fruit juice, oil, or muddy water in a river or the ocean. Incoming light interacts with these participating media in complex ways: refraction at boundaries and scattering and absorption inside volumes. The radiative transfer equation is the key to solving this problem. There are several categories of rendering methods which are all based on this equation, but using different solutions. In this paper, we introduce these groups, which include volume density estimation based approaches, virtual point/ray/beam lights, point based approaches, Monte Carlo based approaches, acceleration techniques, accurate single scattering methods, neural network based methods, and spatially-correlated participating media related methods. As well as discussing these methods, we consider the challenges and open problems in this research area.

Optical Efficiency Enhancement of Nanojet-Based Dielectric Double-Material Color Splitters for Image Sensor Applications

We propose a new type of color splitter, which guides a selected bandwidth of incident light towards the proper photosensitive area of the image sensor by exploiting the nanojet (NJ) beam phenomenon. Such splitting can be performed as an alternative to filtering out part of the received light on each color subpixel. We propose to split the incoming light thanks to a new type of NJ-based near-field focusing double-material element with an insert. To suppress crosstalk, we use a Deep-Trench Isolation (DTI) structure. We demonstrate that the use of a dielectric insert block allows for reduction in the size of the color splitting element. By changing the position of the DTI, the functionality of separating blue, green and red light can be improved.

Efficient Arbitrary Polarized Light Focusing by Silicon Cross-Shaped Metaatoms

Functionalities of most of the metasurfaces that are investigated so far, especially in illuminations with arbitrarily linearly polarized incident light, are restricted to x- or y-polarized incoming light. In particular, filtering out one of the two orthogonal polarizations of the incoming electromagnetic wave loses the incident light energy and limits the potential performance of the metasurface. In this study, by utilizing the cross-shaped silicon metaatoms that support the simultaneous excitation of electric and magnetic dipoles under the illumination of both x- and y- orthogonal polarizations, we overcome the polarization-restricted functionality of the metalenses. By selecting the metaatoms arrangement in the metalens structure, which follows the hyperbolic phase profiles for both x- and y-polarized incoming light waves at the same time, we obtain the light intensity distribution with the extended depth of focus or enhanced intensities at the focal spot with the focusing efficiency 65% for the numerical aperture of 0.7. Utilizing metaatoms with the ability to control the two orthogonal incoming polarizations develops a new methodology for using the full potential and intensity of the arbitrary polarized incoming light. The present design concept of metaatoms has several advantages that are not limited to metalenses alone but can be applied in all metasurfaces realized to have good efficiency. Finally, the proposed metalenses are suitable for imaging, optical tweezer and lithography applications, where subwavelength light intensity distributions with extended depth of focus are the most desirable property.

«Lighting price» of cucumber yield in the winter-spring turnover of greenhouses

Relevance. Among the main factors that determine the productivity of vegetable yields in protected ground, the main one is light. For the formation of 1 kg/m2 of cucumber fruits with a length of 18-22 cm, on average about 3500-4000 J/cm2 of solar radiation is required. In the winter-spring cycle, in the absence of artificial lighting in greenhouses, there is an unevenness of scattered solar radiation and a general shortage of incoming light energy. At the same time, the amount of total solar radiation required for the formation of a 1 kg of fruit ("lighting price") is not the same for different hybrids. To increase the profitability of production in the winter-spring turnover in greenhouses that are not equipped with artificial lighting, it is necessary to choose hybrids with the lowest "lighting price" of the crop, that is, hybrids that use less light energy to form a 1 kg of fruit.The purpose of the study: evaluation of F1 hybrids of cucumber on the basis of resistance to lack of lighting by comparing their "lighting price" of the crop: how much energy is spent on the formation of 1 kg of marketable products.Methods. The research was carried out at the variety testing site in the Crimean breeding Center of the Scientific Research Institute of Vegetable Crop Selection "Gavrish", in the conditions of winter-spring turnover, in greenhouses not equipped with artificial lighting. We tested seven medium-fruited (18-22 cm) spined-fruited cucumber hybrids recommended for growing in winter-spring turnover.Results. The analysis of the data on the input of solar radiation and the formation of a standard yield showed that there is a direct relationship between the amount of incoming light and the level of productivity. The period of conversion of the received solar energy into the fruit harvest varied during the growing season from 14 to 8 days, depending on the degree of plant development. The "lighting price" of the crop was not the same for different hybrids: the hybrids tested in the experiment spent an average of 2900 J/cm2 per 1 kg of product, which is 18% more efficient than for standard greenhouse cucumbers.

Emergency Landing Spot Detection Algorithm for Unmanned Aerial Vehicles

The use and research of Unmanned Aerial Vehicle (UAV) have been increasing over the years due to the applicability in several operations such as search and rescue, delivery, surveillance, and others. Considering the increased presence of these vehicles in the airspace, it becomes necessary to reflect on the safety issues or failures that the UAVs may have and the appropriate action. Moreover, in many missions, the vehicle will not return to its original location. If it fails to arrive at the landing spot, it needs to have the onboard capability to estimate the best area to safely land. This paper addresses the scenario of detecting a safe landing spot during operation. The algorithm classifies the incoming Light Detection and Ranging (LiDAR) data and store the location of suitable areas. The developed method analyses geometric features on point cloud data and detects potential right spots. The algorithm uses the Principal Component Analysis (PCA) to find planes in point cloud clusters. The areas that have a slope less than a threshold are considered potential landing spots. These spots are evaluated regarding ground and vehicle conditions such as the distance to the UAV, the presence of obstacles, the area’s roughness, and the spot’s slope. Finally, the output of the algorithm is the optimum spot to land and can vary during operation. The proposed approach evaluates the algorithm in simulated scenarios and an experimental dataset presenting suitability to be applied in real-time operations.

A Low Dark Current 160 dB Logarithmic Pixel with Low Voltage Photodiode Biasing

Extending CMOS Image Sensors’ dynamic range is of fundamental importance in applications, such as automotive, scientific, or X-ray, where a broad variation of incoming light should be measured. The typical logarithmic pixels suffer from poor performance under low light conditions due to a leakage current, usually referred to as the dark current. In this paper, we propose a logarithmic pixel design capable of reducing the dark current through low-voltage photodiode biasing, without introducing any process modifications. The proposed pixel combines a high dynamic range with a significant improvement in the dark response compared to a standard logarithmic pixel. The reported experimental results show this architecture to achieve an almost 35 dB improvement at the expense of three additional transistors, thereby achieving an unprecedented dynamic range higher than 160 dB.

Numerical & Analytical Modeling of Plasmonic Filter with High Q-Factor Based on "Nanostructured Resonator"

In this paper, to achieve high quality filters, nanostructured plasmon resonators are proposed. The structure of proposed resonator is based on metal-dielectric-metal configuration and is designed in the range of 1550 nm telecommunication wavelength. To evaluate the proposed structure, finite difference time domain method as well as analytical method of coupled mode theory have been used. To obtain optimal results, the effects of the number of waveguides as well as the radius of circular and ring waveguides were investigated. The appropriate results will be obtained by considering a strong coupling between the incoming light and the surface plasmon. In addition, two transient and static wave structures have been used to evaluate the structure. The simulation results show that besides filtering behavior of the structure, it is possible to control the surface plasmon propagation speed in the proposed structure. Therefore, it is expected that the proposed structure will be used in many parts of a telecommunications link, including multiplexers, and multiplexers.

Two-Dimensional Digital Beam Steering Based on Liquid Crystal Phase Gratings

Electrically tunable phase gratings are able to steer an incoming light beam without employing movable parts. Here, we present the design and implementation of a 2D beam steering device by cascading two orthogonal 1D liquid crystal (LC) based phase gratings, each having an array of 72 rectangular individually controlled pixels and driven by a custom 12-bit Pulse-Width Modulation (PWM) electrical driver. High-resolution structures in glass wafers coated with transparent Indium-Tin Oxide (ITO) have been prepared using Direct Laser Writing (DLW) techniques. With DLW, a high number of pixels can easily be drawn with an interpixel space of less than 3 μm, leading to devices with a high fill factor. The active area of the cascaded device is 1.1 × 1.1 mm2. We present a 72 × 72 point efficiency map corresponding to a maximum diagonal steering angle of 1.65°. Special attention has been paid to make the device compatible with space application by avoiding electronics in the active area.

Deep Learning for Transient Image Reconstruction from ToF Data

In this work, we propose a novel approach for correcting multi-path interference (MPI) in Time-of-Flight (ToF) cameras by estimating the direct and global components of the incoming light. MPI is an error source linked to the multiple reflections of light inside a scene; each sensor pixel receives information coming from different light paths which generally leads to an overestimation of the depth. We introduce a novel deep learning approach, which estimates the structure of the time-dependent scene impulse response and from it recovers a depth image with a reduced amount of MPI. The model consists of two main blocks: a predictive model that learns a compact encoded representation of the backscattering vector from the noisy input data and a fixed backscattering model which translates the encoded representation into the high dimensional light response. Experimental results on real data show the effectiveness of the proposed approach, which reaches state-of-the-art performances.