Recent advance in application of acousto-optic tunable filters

Abstract

SThis paper aims to inform those interested in the scientific work of a large group of scientists: workers of the in the area of researches and development of acousto-optic tunable filters (AOTF).Paper discusses the important features of the AOTF structure and their parameters that affect its work, such as: spectral range of optical radiation, spectral resolution, active aperture of the optical radiation, optical transmission of the working spectral range, optical radiation polarization (linear, circular or arbitrary) , diffraction efficiency, contrast, distortion of the optical radiation's front, frequency range of elastic waves, switching time, maximum electric control power, impedance.Also the AOTF using is considered: AOTF's implications for control of laser radiation, AOTF's application to determine the counterfeit money. The last part of the report focuses on materials that act as antireflection thin films.Spectral characteristics of "clean" and enlightened substrates of ZnSe and Ge are shown. As seen from the examples in the report, antireflection thin films increase transmittance of optical elements. I. AOTF OPERATION PRINCIPLESAOTF operational principles are based on elastic waves frequency of forming the grating in the bulk crystal diffracted light selectivity. This phenomenon refers to the characteristics of the anisotropic diffraction of light1. The propagation velocities of the incident and diffracted radiation may significantly differs from each other in an optically anisotropic environment, which leads to various forms of triangles scattering (law of momentum conservation). Acoustic wave propagation also have anisotropy in crystals. For example, there are large deviations in tens of degrees of the acoustic energy flux of the wave vector in the propagation and reflection in the crystal paratellurite which is widely used in acousto-optic devices 2, 3 . These features of the propagation of optical and acoustic waves in crystalline anisotropic environment are used in construction of AO tunable filters of different designs.