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Characteristic features of anisotropic light diffraction in a spatially periodic acoustic field created by a sectioned piezoelectric transducer with antiphase excitation of adjacent sections are studied theoretically. The numerical calculation is carried out for a cell of a paratellurite crystal with a shear acoustic mode propagating at an angle of 3° to the (001) plane of the crystal. It is shown that this type of acoustooptic interaction has some interesting features that can be used when developing acoustooptic devices, in particular, modulators of nonpolarized light.

The circular dichroism in cholesteric liquid crystals (CLCs) has been studied in the absorption bands of dissolved dichroic dyes possessing both the positive and negative linear dichroism. The circular dichroism is studied depending on the position of CLC selective reflection band with respect to the dye absorption band. The induced circular dichroism due to dye absorption is compared to intrinsic CLC circular dichroism due to the light diffraction from the periodic chiral structure.

The Bragg light diffraction on periodic domain structures (PDS) with spatial period of 8.79 μm in MgO:LiNbO3 crystals with 3m symmetry in external electric field has been analyzed. Time dep...

In this paper the measurement methods for extended objects’ geometry on the basis of effect of light diffraction which can be applied to technological control of products with wide range of diameters from the smallest to the largest are described. During measurement the method that allows to minimize the influence of disturbing factors on the results of measurements of diameter of thin fibers of small diameters of micron is described. Disturbing factors include excessive flare of area of the central maximum range. The diffraction method is considered that allows to increase to units of micrometers the resolution of the optical measuring converters used in devices to perform technological control of cylindrical extended products of a large diameter such as: cables, wires, cords, etc. The transformation function allowing to calculate diameter of cylindrical products irrespective of their location in a control zone on the basis of the diffraction method of delimitation of the product shadow in optical two-coordinate converters with the dispersing laser bunch is offered and experimentally confirmed. The achieved results can be used for development of high-precision optical devices of technological control of outer diameter and eccentricity of products for cable, pipe and other products in different industry fields.

Optical tweezers are an essential tool in several areas of physics, spectroscopy, biology, nanotechnology, and thermodynamics. In 1970, Ashkin uses that a focused laser beam can accelerate, decelerate, and even stably capture micrometer-sized neutral particles. Later, in 1986, Ashkin and his colleagues reported the first implementation of optical tweezers: a highly focused beam of light capable of holding microscopic particles in three dimensions. [1], [2] Thanks to this work, Ashkin was awarded the 2018 Nobel Program in Physics. Optical capture is an important method for monitoring and examining particles on scales from nanometers to millimeters. The operation principle of an optical system with the acousto-optical deflector for automatic particle capture is described. We demonstrate that the developed optical system, due to fast frequency tuning of the acousto-optical deflector, provides particle transportation along an arbitrary trajectory and multiple capture mode.

Embryos and microscopes share a long, remarkable history and biologists have always been intrigued to watch how embryos develop under the microscope. Here we discuss the advances in microscopy which have greatly influenced our current understanding of embryogenesis. We highlight the evolution of microscopes and the optical technologies that have been instrumental in studying various developmental processes. These imaging modalities provide mechanistic insights into the dynamic cellular and molecular events which drive lineage commitment and morphogenetic changes in the developing embryo. We begin the journey with a brief history of microscopy to study embryos. First, we review the principles and optics of light, fluorescence, confocal, and electron microscopy which have been key techniques for imaging cellular and molecular events during embryonic development. Next, we discuss recent key imaging modalities such as light-sheet microscopy, which are suitable for whole embryo imaging. Further, we highlight imaging techniques like multiphoton and super resolution microscopy for beyond light diffraction limit, high resolution imaging. Lastly, we review some of the scattering-based imaging methods and techniques used for imaging human embryos.

In this study, the white light diffraction phase microscopy and the generalized Morse wavelet are proposed to achieve practical and precise measurement of a thin film surface. The white light diffraction phase microscopy provides low speckle noise and single-shot measurement, and thus it has been used to produce an image with interference fringes from the surface of a thin film. Relying on produced interferogram, quantitative phase information of the thin film surface has been obtained using the continuous wavelet transform. In the calculation of the quantitative phase, in many studies the continuous wavelet transform method with different wavelets is preferred. The Morlet wavelet is a commonly used one with a fixed resolution. An alternative approach is proposed using the generalized Morse wavelet capable of controlling the resolution. It has an additional advantage of varying the two parameters, thus improving the sensitivity of phase calculation. Results of the generalized Morse wavelet were compared with the Morlet and Paul wavelets which also have one varying parameter. For the determination of the thin film surface profile, besides the white light diffraction phase microscopy, surfaces have been investigated by a Dektak stylus profilometer and a scanning electron microscope. In this way, it was possible to observe the difference between the most commonly used methods with regard to the imaging of thin film surfaces. The application of the white light diffraction phase microscopy with the generalized Morse wavelet was compared with the common microscopy techniques for studying thin film surfaces, and experimental results were discussed at the end of the study. © 2021 Polish Academy of Sciences. All rights reserved. 120F325 This work was supported by the Tekirda? Nam?k Kemal University Scientific Research Project Commission (NKUBAP.01.GA.18.148) and the Turkish Scientific and Technical Research Council (TUBITAK-MFAG No 120F325). This work was supported by the Tekirdağ Namık Kemal University Scientific Research Project Commission (NKUBAP.01.GA.18.148) and the Turkish Scientific and Technical Research Council (TUBITAK-MFAG No 120F325).

We report ensemble learning of diffractive optical neural networks that result in substantial improvements in the all-optical image classification accuracy of the resulting models.

Este proyecto ilustra de qué manera los catálogos de video con proceso curatorial basado en datos pueden ofrecer un enfoque para analizar secuencias de video. Tenien­do ricas y diversas colecciones de video como input, los catálogos basados en datos buscan identificar objetos comunes y reor­ganizarlos en clústeres temáticos que se muestran en formato de video. La técnica se inspira en dos prácticas científicas (el mues­treo de núcleos y la difracción de la luz) y en dos formatos de publicación (los supercuts y los catálogos visuales). Los catálogos de video con proceso curatorial basado en da­tos se utilizan para republicar una colección de imágenes de la marea alta de Venecia de 2019, la que devastó la ciudad en forma inédita. A partir de una selección editorial de imágenes extraídas de YouTube, se utilizan varios procesos algorítmicos para demarcar y reorganizar el material en series temáticas de videos (personas, barcos y pájaros). Los catálogos de video resultantes permiten un tipo de análisis visual que va más allá de las formas tradicionales de medición, al tiempo que presentan un poder expresivo.

The resolution achieved by conventional light microscopy is limited by light diffraction. This obstacle can be overcome either by optical super-resolution techniques or by the recently developed method to physically expand specimens, called expansion microscopy (ExM). The method utilizes polymer chemistry and the ability of a swellable polyelectrolyte hydrogel to absorb water, and thus to expand its size. The procedure was successfully applied to different species and tissue samples, mostly from the animal kingdom. Physically expanded nuclei and chromosomes in combination with specific protein labeling and super-resolution microscopy may provide new insight into the ultrastructure, dynamics, and function of plant chromatin. Here we provide a detailed protocol to expand isolated plant nuclei and visualize proteins by indirect immunolabeling. With the focus on chromatin structure, we expanded isolated barley nuclei from root tips and visualized the centromere-specific histone H3 variant CENH3. The achieved physical expansion of ~4.2 times allowed the detection of DAPI-labeled chromatin structures already by conventional wild-field (WF) microscopy with a maximal resolution of ~50-60nm. By applying structured illumination microscopy (SIM), doubling the WF resolution, chromatin structures at a resolution of ~25-35nm were observed. However, a certain distortion of the centromeric chromatin ultrastructure became obvious.

Recently proposed methods of bacteria identification in optical biosensors based on the phenomenon of light diffraction on macro-colonies offer over 98% classification accuracy. However, such high accuracy relies on the comparable and repeatable spatial intensity distribution of diffraction patterns. Therefore, it is essential to eliminate all non-species/strain-dependent factors affecting the diffraction patterns. In this study, the impact of the bacterial colony and illuminating beam misalignment on the variation of classification features extracted from diffraction patterns was examined. It was demonstrated that misalignment introduced by the scanning module significantly affected diffraction patterns and extracted classification features used for bacteria identification. Therefore, it is a crucial system-dependent factor limiting the identification accuracy. The acceptable misalignment level, when the accuracy and quality of the classification features are not affected, was determined as no greater than 50 &micro, m. Obtained results led to development of image-processing algorithms for determination of the direction of misalignment and concurrent alignment of the bacterial colonies&rsquo, diffraction patterns. The proposed algorithms enable the rigorous monitoring and controlling of the measurement&rsquo, s conditions in order to preserve the high accuracy of bacteria identification.

We propose a novel scheme for asymmetric light diffraction of a weak probe field into a one-dimensional (1D) and two-dimensional (2D) lattice occupied with cold atoms. The atoms are driven into the double lambda-type configuration by a standing wave, two coupling laser fields and a probe. Our study suggests the proposed scheme is capable of forming an asymmetric diffraction as a result of inducing optical parity-time symmetry in both 1D and 2D lattices. Moreover it is demonstrated that the asymmetric pattern of diffraction can be dynamically manipulated by means of adjusting the relative phase. Furthermore it is revealed that in the case of 1D lattice (grating), variation of the intensities of the coupling fields has a significant impact on the intensity of diffraction orders in the uneven distribution of diffraction., 15 pages, 7 figures

Periodični sistemi igrajo pomembno vlogo v znanosti in tehnologiji. V začetku 20. stoletja je bila razvita rentgenska kristalografija, ki je izkoristila uklon svetlobe na periodični zgradbi snovi za določanje njene mikroskopske sestave. Uklon opazimo, ko svetloba posega za oviro ali v odprtino z velikostjo, ki je primerljiva z njeno valovno dolžino. V nalogi sem iz interferenčne slike svetlobe določila strukturo LCD zaslona. Iz nastale interferenčne slike sem določila obliko posameznega slikovnega elementa in razporeditev le teh. Dodatno sem sestavo zaslona preverila s svetlobnim mikroskopom in naredila primerjavo med mikroskopsko sestavo in interferenčno sliko. Periodic systems play an important role in science and technology. In the early 20th century, X-ray crystallography was developed, which took advantage of the diffraction of light on periodic structure of matter to determine its microscopic composition. Here I present the study of interference image of light from a digital screen with a goal to determine its structure. From the interference image, I determined the shape of each pixel and the grid parameters. I additionally checked the structure of the screen with a light microscope and made a comparison between the microscopic structure and the interference image.

Flexible and high-efficiency thermoelectric devices can be achieved by relying on three-dimensional nanostructures fabricated by proximity-field nanopatterning (PnP) process. In this study, the phase shift mask, which generates the light diffraction in the photoresist, has been studied. To enhance device performance, the size limitation of the mask for this process was investigated as well as how the mask affects the device performance in light propagation simulations. Results show that decreasing the nanostructure size by altering the periodicity from 0.60 µm to 0.30 µm results in 50 % filling factor (FF). To summarize, the mask periodicity 0.30 µm is the size limitation performed by simulation, and the mask periodicity 0.40 µm is an exciting candidate for future work.

The width of a human hair sourced from a female elementary school student was measured by light diffraction using red and blue laser pointers. The two laser sources both provided consistent estimates of the hair diameter of approximately 50 μm. The overall experiment and writing process provided a temporary respite from COVID-19 shelter-in-place requirements and deteriorating spring weather that precluded outdoor activities.

International audience; We propose a method to pattern organic optically active materials based on local photo-bleaching for making wavelength selective grating. Usually, photo-bleaching is considered as a limitation for organic emitter. Here, this property is exploited to locally suppress dye emission and absorption at the microscale with abrupt interface and no changes in layer thickness. Periodic patterns were fabricated and exhibit diffraction only at 590nm wavelength with spectral selectivity of 11nm. Based on laser writer flexibility and efficiency, this study shows the potential of local photo-bleaching for several applications like wavelength selective grating fabrication.

Laser-induced ripples that are also known as laser-induced periodic surface structures (LIPSS) have gained a considerable attention by researchers and industry due to their surface functionalization applications. However, texturing large areas or batch manufacture of parts that incorporate LIPSS surfaces require the development of tools for monitoring the LIPSS generation and potentially for controlling their main geometrical characteristics, i.e., spatial periodicity, orientation, and amplitude. In this context, the focus of the research reported in this paper is on developing process monitoring and inspection methods for identifying shifts and changes in these characteristics. One of the well-known and widely used by industry method for characterizing and inspecting surfaces is light scattering, and this research investigates the capabilities of this method for inline monitoring of LIPSS optical response. A simple setup was designed and implemented for measuring the diffraction angle and intensity of the reflected light from LIPSS surfaces. The capabilities of this concept for determining relative shifts in the optical response on surfaces processed with known disturbances, such as incident angle deviations and focus offset, were investigated. Sensitivity of the method proved to be sufficient to detect shifts/deviations from LIPSS reference and thus potentially to monitor their generation in line with a simple sensor, e.g., the LIPSS treatment of larger tool surfaces or serial manufacture of holograms.

We consider one of the mechanisms providing light diffraction in layered structures disturbed by ultrasound. We show that diffraction can be observed when light is reflected from the surface in an area where there is no acoustic wave. Diffraction occurs due to the fact that the light receives a curved phase front when passing through an acoustic column.

Micro-scale patterning of alignment layers with focused ion beam produces liquid-crystal-metasurfaces with strong diffraction. We study the electro-optical switching from diffraction to transmission mode and show that it occurs within milliseconds.

Liquid-crystal-metasurfaces self-assemble on polymer films prepared by periodic and superperiodic FIB patterning. Optimizing their design we achieve precise control of the transmitted light phase and direction tunable by low-voltage electric pulses.

Accepted manuscript version. Published version available at https://doi.org/10.1016/j.pocean.2018.09.002. Accepted manuscript version, licensed CC BY-NC-ND 4.0. Light and its interaction with microalgae are essential concerns in the context of microalgae studies. The optical properties of microalgae have a great impact on the remote sensing ocean color, underwater light distribution and biomass accumulation, to mention some areas. A deep understanding of these processes requires knowledge on both the physical light interaction mechanisms with algae, and effects in cellular photophysiology and eventually primary production. Therefore, in this review we comprehensively explain the fundamental physical principles behind microalgae optical properties addressing the multidisciplinary microalgae community. We try to answer what happens with light in the microalgal cell on the cellular and molecular level, and explain the physical mechanisms of light absorption, scattering, fluorescence and diffraction. The current optical cell models that describe the absorbance and scattering properties of microalgae are compared and reviewed. The recent discoveries of the behavior of light in diatom frustules and coccolithophore coccoliths are represented, also showing the special role of these microalgae groups in terms of light interaction. Because microalgae and light are reciprocally interacting, we will briefly also view the photoacclimation and chromatic regulation associated with physical, metabolic and gene transcriptory changes. Finally, predictions and suggestions on the future research directions within oceanography, limnology, remote sensing and aqua culture are provided.

Three acousto-optic materials, ТеО2, SiO2, and LiNbO3, widely used in production of acousto-optic cells for pulse modulation of the multicolor optical radiation, have been compared. It is demonstrated that the ТеО2 acousto-optic cell has an undoubted advantage in terms of the electric power consumption, first of all, due to its high acousto-optic figure of merit, while SiO2 and LiNbO3 cells are preferable from the viewpoint of the lowest distortions in transformation of electrical pulses into optical signals. Main theoretical conclusions have been confirmed by experiments on modulation of the multicolor Ar laser radiation.

Background When a plant is wounded, a rapid hydraulic surge, acting probably as a systemic signal, spreads from the site of injury throughout the plant and leads to small transient deformation of tissues. So far, the propagation of hydraulic surge has been monitored by contact and thus potentially invasive methods. Results Here we present a non-invasive optical method, which allows simultaneous monitoring of micrometric shift of two opposite stem margins. The usefulness of this method was demonstrated by the measurement of the hydraulic surge propagation in a tobacco (Nicotiana tabacum (L.) cv. Samsun) after burning of its upper leaf. We have observed transient narrowing the stem below the burned leaf, which started within a few minutes after local burning. The comparison of the shift of the stem margin following vascular trace of the burned leaf and the margin on the opposite side of the stem has revealed that the stem deformation is highly asymmetric. Conclusions This optical method represents a novel tool to investigate the mechanism of systemic response of plants to local damage. Our results points out the complexity of the relationship between hydraulic surge propagation and stem deformation. Electronic supplementary material The online version of this article (10.1186/s13007-018-0307-6) contains supplementary material, which is available to authorized users.

Rosalind Franklin's X-ray diffraction patterns of DNA molecules rendered the important clue that DNA has the structure of a double helix. The most famous X-ray photograph, Photo 51, is still printed in most Biology textbooks. We suggest two optical experiments for undergraduates that make this historic achievement comprehensible for students by using macromodels of DNA and visible light to recreate a diffraction pattern similar to Photo 51. In these macromodels, we replace the double helix both mathematically and experimentally with its two-dimensional (flat) projection and explain why this is permissible. Basic optical concepts are used to infer certain well-known characteristics of DNA from the diffraction pattern.

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.

This work presents a research of the diffraction of light on the multilayer inhomogeneous holographic diffraction structures (MIHDS) in a photopolymer material (PPM) under photoinduced light absorption (PIA) conditions. Considering PIA, the authors showed possible distortions of the selective response of the diffracted beam due to the heterogeneity of the profiles of lattices over the depth of the layer.

The microorganisms identification can be achieved by light diffraction phenomenon leading to the generation of unique optical signatures. This paper is focused on an alternative configuration of the integrated optical biosensor at fixed incubation time, which makes possible the integration of the proposed system into automated specimen processing workflow common for microbiological laboratories. Influence of the intensity distribution of the illuminating beam and iris diaphragm diameter on the deformation of diffraction is indicated. The crucial influence of the registration distance on classification accuracy is indicated as an essential factor limiting the identification, what was confirmed by analysis of over 48 400 patterns. The complex examination of the accuracy of the proposed technique is performed based on highly representative data containing over 100 000 patterns of 12 species including 88 strains. The proposed method enables the identification with accuracy between 97 and 100%.