Mechanisms of multi-layered Rayleigh noise in Brillouin optical correlation-domain reflectometry.

In Brillouin optical correlation-domain reflectometry (BOCDR), sinusoidal modulation is applied to the output frequency of a light source, with spatial resolution inversely related to the modulation amplitude. We have developed an effective method to estimate the modulation amplitude using the width of the noise spectrum caused by Rayleigh scattering, eliminating the need for an optical spectrum analyzer or modifications to existing equipment. However, the Rayleigh noise spectrum often displays a three-layered structure, complicating the identification of the appropriate spectral components for estimating the modulation amplitude.

Design and fabrication of a liquid crystal polarization grating for mid- and far-infrared wavelengths.

A lot of research on liquid crystal polarization gratings (LCPGs) that can separate circularly polarized light with 100% diffraction efficiency has been conducted in the visible and near-infrared wavelength regions. In this paper, we tried to design and fabricate the LCPGs that are available for use in the mid- and far-infrared (MIR and FIR) wavelength regions. The materials for making LCPGs were selected in view of low absorption characteristics measured by the use of a Fourier-transform infrared (FT-IR) spectrometer.

Design of two-dimensional multilevel optical anisotropic diffraction gratings with a generative adversarial network.

This study uses a generative adversarial network to design multilevel optical anisotropic diffraction gratings with specific customizable characteristics. As input, this method uses the far electric field of polarization and intensity in each diffracted light through the gratings to design. Using the finite-difference time-domain method, the designed structures are numerically evaluated, confirming that they can be created with the intended parameters.

Systematic-error suppression in low-coherence Brillouin optical correlation-domain reflectometry.

Brillouin optical correlation-domain analysis (BOCDA) utilizing low-coherence light sources offers high-resolution distributed strain and temperature sensing. However, conventional BOCDA requires dual-end injection of pump and probe light into the sensing fiber. To overcome this limitation, low-coherence Brillouin optical correlation-domain reflectometry (BOCDR) based on spontaneous Brillouin scattering has emerged, enabling single-end light injection.

Polarization-probe polarization-imaging system in near-infrared regime using a polarization grating.

A polarization-probe polarization-imaging (PPPI) system was developed for the near-infrared (NIR) regime. This system comprises two components operating as a polarization generator and a polarization analyzer to enable polarization image capture under polarized light illumination. The captured polarization images contain considerable object information because the illuminating polarized light beams are affected by many of the Mueller matrix elements.

Hybrid polarization grating for mode detection of vector beams.

A hybrid polarization grating that can spatially separate orthogonal states of a vector beam with the same polarization topological charge is presented. The hybrid polarization grating is assembled using a fork-shaped polarization grating and a quarter-wave polarization grating and acts as a common pass interferometer for right- and left-circular polarization components of incident vector beams. The hybrid polarization grating can separate two vector beam states that have a 90 ° relative polarization azimuth angle difference.

Magnification and wavefront aberration correction by a geometric-phase lens in a polarized aerial display using a right-angle prism.

In this paper, geometric-phase lenses, which can not only correct wavefront aberrations but also magnify an aerial image, have been proposed for use in an aerial display system composed of a retroreflector array, an orthogonal-circular polarization grating, a right-angle prism, and a quarter-wave plate. The geometric-phase lenses were demonstrated both experimentally and computationally by arranging them in the aerial display configuration and observing aerial images. We also investigated the relationship between the magnification and the field of view of an aerial image, and it has been found that there is the trade-off relationship between them.

Brillouin optical correlation-domain reflectometry based on arbitrary waveform modulation: a theoretical study.

We put forward a new theory on Brillouin optical correlation-domain reflectometry (BOCDR) based on arbitrary waveform modulation. We derive a universal representation for the spatial resolution using the foot convexity of the beat spectrum. This result well explains the previous results based on sinusoidal modulation, and thus our theory is the consistent extension of the conventional theory on BOCDR.

Polarized beam steering using multiply-cascaded rotating polarization gratings.

A polarized laser beam steering system using multiply cascaded rotating polarization gratings (PGs) is presented. The rotating PGs steer incident circularly polarized beams with high optical throughput because the theoretical limitation of the PG diffraction efficiency is 100%. The system also offers more rapid rotation when compared with wedge prism pairs because of the weight of the PGs.

Structural Characteristics of Monomeric Aβ42 on Fibril in the Early Stage of Secondary Nucleation Process.

Amyloid-β (Aβ) aggregates are believed to be one of the main causes of Alzheimer's disease. Aβ peptides form fibrils having cross β-sheet structures mainly through primary nucleation, secondary nucleation, and elongation. In particular, self-catalyzed secondary nucleation is of great interest.

Incident angle dependence-reduced polarization grating performance by using optically biaxial polymer liquid crystal.

We have succeeded in forming a polarization grating whose polarization diffraction properties are extremely independent of the incident angle by using polymer liquid crystal exhibiting biaxial optical anisotropy. It is considered that the extension of the optical path length and the decrease in the effective amplitude of optical anisotropy due to oblique incidences are offset by the biaxial optical anisotropy and, as a result, the retardation is compensated. The properties of this developed device have been experimentally demonstrated and theoretically explained.

White-light circular-polarization imaging using pairs of polarization gratings and wedge prisms.

A novel, to the best of our knowledge, method for circular-polarization imaging with white light is presented. The vital optical elements of the proposed system are two polarization gratings (PGs) and a wedge prism. The chromatic dispersion of the PG diffraction angle is compensated by the difference of the grating period for the two PGs.

High-efficiency aerial display using a liquid crystal polarization grating, a retroreflector array, and a right-angle prism.

An aerial display scheme consisting of an orthogonal circular polarization grating (OCPG), a waveplate, a retroreflector array (RRA), and a right-angle prism (RAP) was developed. Because of the OCPG's functionality, retroreflected light from the RRA is transmitted through the RAP boundary surface by avoiding the total reflection condition. The proposed system can potentially increase optical throughput to 100% by designing the boundary surface incidence angle to be Brewster's angle.

Colocalization of GPR120 and anterior pituitary hormone-producing cells in female Japanese Black cattle.

Negative energy balance in domestic animals suppresses their reproductive function. These animals commonly use long-chain fatty acids (LCFAs) from adipocytes as an energy source under states of malnutrition. The G-protein coupled receptor, GPR120, is a specific receptor for LCFAs, but its role in reproductive function remains unknown in domestic animals.

Prepartum change in ventral tail base surface temperature in beef cattle: comparison with vaginal temperature and behavior indices, and effect of ambient temperature.

Prediction of parturition is essential for sustainable production in beef and dairy cattle, yet the present methods are limited by their high invasiveness and low utility. Here we compared prepartum changes in ventral tail base surface temperature (ST) with changes in vaginal temperature (VT) and behavioral indices. We analyzed 22 parturitions from 22 beef cows.

Generation of optical vortices using a uniaxially aligned azo-dye-doped liquid crystal cell and space-variant polarization projection system.

A scheme is presented for an optical vortex (OV) generator comprising a uniaxially aligned azo-dye-doped liquid crystal (ADDLC) and a space-variant polarization projection (SVPP) system. The SVPP system consisting of an electro-optic modulator and a micro-electromechanical system projects a time-averaged SVP field equal to a vector beam onto the ADDLC and fabricates a three-dimensional twisted anisotropic structure, which has spatial phase modulation properties from plane to helical shape. The generation of OVs with odd- and even-numbered topological charge is experimentally demonstrated.

Dynamic control of diffraction angle and separation properties of wavelength and polarization by quaternary liquid crystal grating.

A quaternary liquid crystal (LC) grating simultaneously performs dynamic control of diffraction angle, polarization, and wavelength-separation properties as shown in the following: (1) Diffraction orders in which light waves are diffracted can be selected by applying a voltage, (2) the efficiency of each diffraction order can be controlled depending on a wavelength of an incident beam, and (3) a pair of counter-rotated circular polarizations or linear polarizations with an orthogonal relationship are diffracted simultaneously, and this property can be controlled by applying a voltage. These diffraction properties and LC alignment structures are proposed based on theoretical analyses using Jones calculus, and their properties are now demonstrated experimentally. The quaternary LC grating can be used as an advanced optical element for industrial applications such as tunable polarization beam splitters and dynamic switching of propagation directions of light depending on wavelength.

Diffraction properties of liquid crystal cell with beat structure formed by photoalignment substrates.

The diffraction properties of liquid crystal (LC) cells fabricated by photoalignment substrates with different periodic optical anisotropic distributions are demonstrated. The twist angle distribution structure inside the LC cells formed by the grating period difference between photoalignment substrates is called "beat structure." In addition to diffraction corresponding to the grating periods of photoalignment substrates, beat structure itself also functions as a diffraction grating.

Polarization imaging using an anisotropic diffraction grating and liquid crystal retarders.

We present a simple yet versatile and practical polarization camera for imaging full Stokes parameters. The developed system consists of one anisotropic diffraction grating plate and two electro-switchable retarders and obtains in nearly real-time full Stokes images of the light scattered from the objects. The monochromatic S image is obtained by physically separating the right and left circularly polarized components with the aid of the anisotropic grating, and S and S images are obtained by fast electro-switching the retardation of each retarder.

Flexible and achromatic generation of optical vortices by use of vector beam recorded functionalized liquid crystals.

In this study, we investigated the spatial light modulation properties of an optical vortex (OV) generator consisting of azo-dye-doped polymer liquid crystal (ADDLC) and a vector beam illuminator, focusing on flexibility and achromaticity for generating OVs. Uniaxially aligned ADDLC forms three-dimensional photoinduced twisted anisotropic structures under vector beam illumination, and can generate high-order OVs with even-numbered topological charges that correspond to the polarization pattern of the illuminating vector beam. The induced anisotropic structure can be re-initialized by turning it off and changing the vector beam polarization distribution.

Design and fabrication of a tunable wavelength-selective polarization grating.

Tunable wavelength-selective diffraction with polarization conversion is realized by the design of a liquid crystal (LC) grating containing a twisted nematic alignment structure that is fabricated by an efficient one-step photoalignment method. The diffraction efficiency strongly depends on the wavelength of the incident beam, and this property can be controlled by adjusting the birefringence of the nematic LC using a thermal control. These properties are well described by a theoretical analysis based on the Jones calculus and are experimentally demonstrated using 488, 532, and 633 nm wavelength incident polarized laser beams.

Holographic liquid crystal polarization grating with Fabry-Perot structure.

A holographic liquid crystal polarization grating with a Fabry-Perot structure was developed. Because of its resonant structure, the device offers high levels of control of the diffraction properties of incident-polarized light beams, depending on the resonance conditions. The diffracted light beams are emitted in both the reflection and transmission directions, and the device thus works as a multibranch polarization grating with double optical paths, unlike a conventional polarization grating.

Three-dimensional vector recording in polarization sensitive liquid crystal composites by using axisymmetrically polarized beam.

Three-dimensional anisotropic structures were fabricated by a recording axisymmetrically polarized beam in azobenzene (azo)-dye doped liquid crystal polymer composites. Polarization and wavefront modulation properties of fabricated anisotropic structures are investigated by experimentally and theoretically analyzing the diffraction properties. Photo-induced anisotropic structures would be utilized to generate singular light waves, such as optical and polarization vortices.

Holographic binary grating liquid crystal cells fabricated by one-step exposure of photocrosslinkable polymer liquid crystalline alignment substrates to a polarization interference ultraviolet beam.

Holographic binary grating liquid crystal (LC) cells, in which the optical anisotropy was rectangularly modulated even as the grating was fabricated using holographic exposure, were fabricated by one-step polarization holographic exposure of an empty glass cell, the interior of which was coated with a photocrosslinkable polymer LC (PCLC). The present study is of great significance in that three types of holographic binary grating LC cells containing twisted alignments can be fabricated by simultaneous exposure of two PCLC substrates to the UV interference beams, which are sinusoidally modulated. The polarization conversion properties of the diffracted beams are explained well by theoretical analysis based on Jones calculus.