The polarization properties of a two-channel spatial AO filter based on diffraction into two symmetric Bragg orders have been studied. A regime is demonstrated where during Fourier processing of an image, the contours in different channels are formed in different polarizations and at different acoustic frequencies. This regime was confirmed experimentally on the basis of optical Fourier processing of an image transmitted by radiation with an optical wavelength of 0.63 μm. As a spatial frequency filter, an AO cell manufactured of paratellurite was used. This made it possible to form the image contour in one channel at a sound frequency of 34 MHz and in another channel at a frequency of 42 MHz.

We report a theoretical and experimental investigation of two-dimensional Fourier processing of an image using two channels when the image is differentiated in one channel and integrated in the other. Both operations are carried out by one acousto-optical (AO) spatial frequency filter operating in the AO diffraction regime in two symmetrical Bragg orders. The transfer functions of the channels are analyzed and differentiation and integration operations are demonstrated. The results are confirmed experimentally through optical Fourier processing of an image formed by radiation at a wavelength of 0.63 μm. An AO cell made of TeO2, operating at a sound frequency of 44 MHz, is used as a spatial frequency filter.

High-quality ZnS epitaxial layers are grown on GaP semiconductor substrates by the MOCVD method. Photodetectors for the visible and UV parts of the spectrum based on interdigital Schottky metal–semiconductor–metal (MSM) barrier contacts to the ZnS/GaР semiconductor structure have been fabricated and studied. The detectors exhibit low dark currents. The dependence of the characteristics of the spectral response of the detectors on the bias voltage is established. It was found that the long-wavelength response limit of ZnS/GaP MSM detectors can shift from 355 to 450 nm when the bias voltage is changed from 10 to 30 V. At the maximum photosensitivity wavelength of 450 nm, the ampere–watt sensitivity of the detector was 0.3 A/W at a bias voltage of 60 V, and the quantum efficiency is 82

The possibility of formation of a 2D optical image contour during double Bragg’s diffraction simultaneously in two Bragg’s orders is investigated. Transfer functions of Bragg’s orders of double diffraction are obtained with account for ellipticity of optical beams and the curvature of wave surfaces of the crystal. The conditions for obtaining the image contour simultaneously in the zeroth and plus second Bragg’s orders are determined. This is confirmed experimentally using the example of Fourier processing of the image transferred by radiation at a wavelength of 0.63 μm. Double Bragg’s diffraction is realized based on an acousto-optic cell made of a uniaxial gyrotropic paratellurite crystal, which operates at an acoustic frequency of 20.3 MHz.

The spectral response and quantum efficiency of the visible-range photodetectors based on ZnSe and ZnCdSe/ZnSe heterostructures are experimentally studied. The spectral response of the detectors is characterized under various bias conditions. A model of a decrease in the effective height of a reverse-biased Schottky contact under irradiation is used to interpret the internal amplification of the detectors.

The results of experimental study of the metal-semiconductor-metal (MSM) photodiode based on ZnCdSe/ZnSSe/GaAs heterobarrier structure are presented. MSM-diode with 2.8 μm Ni-Au interdigitated Schottky barrier contacts, gaps between them of 3 μm, and total detector area of 100 × 100 µm 2 have been fabricated and investigated. At a wavelength of 460 nm MSM-diode provides a high spectral selectivity with FWHM of spectral response 4.3 nm, high current sensitivity of 2.27 A/W and low dark current of 200 pA at 30 V bias. The spectral response of the MSM-detector was characterized under various bias conditions. A reduced Schottky barrier height model was adopted to explain the gain mechanism of the MSM-detector under illumination.

Properties of a two-channel acousto-optic (AO) spatial frequency filter deflecting optical beams in two symmetrical orders are studied. It is found that the non-uniform distribution of the field in each order makes it possible to process images in two channels using different transfer functions. The formation of a two-dimensional contour in two diffraction orders is confirmed experimentally on the basis of image processing for a wavelength of 0.63 mu m. A TeO2 AO cell operating at an acoustic frequency of 26 MHz is used as a two-channel spatial frequency filter.

The characteristics of an acousto-optic spatial frequency filter designed for processing of two-dimensional images and operation in the intermediate region of acousto-optic diffraction are investigated. The advantage of such filters over filters operating in a Bragg regime is the possibility of operation at significantly lower acoustic frequencies, which allows the passband of spatial frequencies to be increased and the limiting resolution to be decreased. Transfer functions of diffraction orders are obtained. The use of the first diffraction order is demonstrated to allow selection of the two-dimensional image contour. The two-dimensional image edge enhancement of the image transmitted by optical emission at a wavelength of 0.63 x 10(-4) cm is experimentally demonstrated using a TeO2 spatial filter operating at a frequency of 15 MHz. (C) 2022 Optica Publishing Group

We propose an approach for producing a rotating polarization vector of dichromatic light controlled by the acoustic frequency. This approach is based on diffraction of one of the eigenmodes for each monochromatic component during two passes of dichromatic light through a gyrotropic acousto-optical cell and is demonstrated using rotation in the polarization of dichromatic light generated by an Ar laser at wavelengths of 0.488 µm and 0.514 µm using a paratellurite acousto-optical cell operating at 108 MHz.

The results of experimental studies of photodiodes based on interdigital MSM (metal–semiconductor–metal) Schottky barrier contacts to a ZnCdSe/ZnSSe/GaAs heterobarrier structure are presented. The detector provides a narrowband response (FWHM = 4.3 nm) at a wavelength of 460 nm, a sharp drop in the photosensitivity in the short-wavelength part of the response signal, high ampere-watt sensitivity, and low dark current.

A method for calculating the parameters of a pulsed acousto-optic modulator of multicolored laser radiation is developed. The parameters make it possible to determine the optimal conditions for the modulation of a specified light spectrum at the maximum sound frequency. The method is experimentally confirmed using an acousto-optic modulator based on paratellurite designed for the modulation of argon laser radiation in the blue–green spectral range.

The effect of a ZnSe/ZnS/GaAs distributed Bragg reflector on the spectral response of a metal–semiconductor–metal (MSM)-diode is investigated. Good agreement is obtained between the calculated and experimental reflection spectra of the ZnSe/ZnS/GaAs heterostructure forming a distributed Bragg reflector in the MSM-diode. The MSM-detector provides a two-color response at 420 and 472 nm, a sharp decrease in photosensitivity in the long-wave part of the response signal, high quantum efficiency of 53%, and low dark current of 5 × 10−10 A. The two-color response of the detector can be adjusted to the desired wavelength by appropriately selecting the heterostructure parameters.

The process of two-dimensional image edge enhancement with an acousto-optical spatial filter using two orders of light diffraction is studied. It is theoretically shown that the diffraction that occurs in a paratellurite crystal on a 'slow' acoustic wave propagating orthogonally to the optical axis of the crystal allows enhancing a two-dimensional edge of an image, transferred by optical radiation with a wavelength of 0.63 mm in a wide band of acoustic frequencies 25 - 50 MHz. Enhancement of a two-dimensional image edge at an acoustic frequency of 29 MHz is experimentally demonstrated.

Bragg diffraction which provides effective acoustooptic interaction of three-color radiation with a single acoustic wave at a high frequency of sound is proposed and tested in a single crystal of paratellurite at the wavelengths of λ = 0.488, 0.514, and 0.633 μ m. Maximal diffraction efficiency of radiation with λ =0.633 μ m at acoustic frequency of 150 MHz is 88% and that with λ = 0.488 μ m and λ =0.514 μ m is 60%. In diffraction efficiency range from 0 to 40% the dependence of all beams on acoustic power is the same.

Abstract—A two-channel high-frequency acousto-optic (AO) modulator-splitter has been developed, which splits optical radiation into two equal optical channels and modulates the intensities of the output channels at double the sound frequency. The modulator makes it possible to simply change the polarization of the output beams. A model of a modulator made of a TeO2 single crystal was used to modulate and split radiation with a wavelength of 0.63 × 10–4 cm. Intensity modulation of the output channels at a frequency of ~200 MHz was achieved.

Effect of the ZnSe/ZnS/GaAs distributed Bragg reflector (DBR) on the parameters of the spectral response of a photodiode based on rectifying contacts in the metal–semiconductor–metal (MSM) system is studied. The calculated photoreflection spectra of the ZnSe/ZnS/GaAs heterostructure are in good agreement with the experimental data. It is shown that the MSM diode provides two-color response of the photodetector at wavelengths of 420 and 472 nm, a sharp decrease in the photosensitivity in the long-wavelength part of the response signal, high quantum efficiency (53%), and low dark current (5 × 10–10 A). It is demonstrated that the narrow-band two-color response of the detector can be tuned to the desired wavelength using appropriate selection of the parameters of the heterostructure that forms that Bragg reflector.

A method of acousto-optical (AO) Bragg diffraction is proposed that provides the amplitude modulation of optical radiation at a doubled acoustic frequency. The method is based on the double transmission of the light through the AO modulator made of a gyrotropic crystal and is experimentally tested by the example of the modulation of light with a wavelength of 0.63 mu m, controlled by the paratellurite AO cell.