Acousto-Optic Devices Based on Multibeam Diffraction
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RAL EXPERIMENTAL TECHNIQUE
Acousto-Optic Devices Based on Multibeam Diffraction S. N. Antonova,* and Yu. G. Rezvovb,** a
Kotelnikov Institute of Radio Engineering and Electronics, Russian Academy of Sciences (Fryazino Branch), Fryazino, Moscow oblast, 141190 Russia b Novomoskovsk Institute of Mendeleev University of Chemical Technology, Novomoskovsk, Tula oblast, 301665 Russia * e-mail: [email protected] **e-mail: [email protected] Received March 19, 2020; revised April 30, 2020; accepted May 4, 2020
Abstract—The multibeam acousto-optical Bragg diffraction of laser radiation is considered. This is splitting of an initial beam into several independently controlled beams (channels) without substantial light-power losses. Practically significant relationships that determine the conditions for implementing the multibeam diffraction and its main parameters have been obtained. It is shown that the necessary condition is the form of control radio signal that is close to a frequency (phase) modulated signal. Experimental studies were conducted on a polarization-insensitive acousto-optic deflector based on a paratellurite crystal. Practical applications of the multibeam diffraction are shown: laser image deposition, multichannel transmission (switching) of optical information, and the formation of the laser-beam profile. DOI: 10.1134/S0020441220050267
1. INTRODUCTION Applied acousto-optics (AO) involves the control of the parameters of optical radiation by ultrasonic waves that propagate in transparent media [1–8]. A practically significant optical range of radiation extends from ultraviolet (UV) to tens of micrometers, while the acoustic range extends from units to hundreds of megahertz. The use of AO in radio-signal analyzers, devices for spectral processing of optical images, in optical processors, etc., has been studied well. The fundamental features of AO devices include the ability to control intense (tens and hundreds of kilowatts per square centimeter) laser radiation, a high response speed (up to tens of nanoseconds), the absence of mechanically movable elements, low introduced optical losses (units of percent), and small dimensions and weight. The development of laser sources also determines the improvement of methods for controlling the radiation parameters: the laser-beam intensity (modulators) and the angular beam position (deflectors). Acoustooptical (AO) modulators are used to modulate the quality factors of lasers and for external modulation of radiation; AO deflectors (AODs) are designed for scanning a laser beam in systems for material processing and laser outputting of images. The main material of modern AO devices is paratellurite (TeO2) single crystals. This crystal has a phenomenally high AO-quality value, М2 = 1000 × 10–18 s3/g (for light diffraction at a slow shear acoustic mode); a
wide range of transparency, from 0.35 to 5 μm; the high radiation resistance; and the developed technology for the production of large (with a side of more than 20 mm) homogeneous crystals [9]. The theory of AO on TeO
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