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22 May 2020 Limit values of reflectivity of the periodic structure created by ultrasound in a crystal
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Proceedings Volume 11516, Optical Technologies for Telecommunications 2019; 115160M (2020) https://doi.org/10.1117/12.2566345
Event: XVII International Scientific and Technical Conference "Optical Technologies for Telecommunications", 2019, Kazan, Russian Federation
Abstract
Theoretical analysis of light diffraction on a periodic structure by using exact analytical solutions of the equations and numerical computer calculations has been conducted. The influence of different apodization functions on diffraction curves of reflection and transmission is studied and their comparative analysis is performed. Complete elimination of oscillating sidelobes and a significant suppression of the “tails” of a diffraction reflection curve are achieved for the specific functions of spatial apodization. The maximum values of the reflectivity of the medium with periodic dielectric permittivity are determined. The effects of light absorption in the crystal and moving gratings on the spectral resolution are evaluated. The Fabry-Perot resonator formed by two spatially-distributed “mirrors” is also studied. A significant increase in spectral resolution of filter due to the spatial variation of the refractive index of the medium is shown. It is shown that the high purity crystals are needed to observe the considered effects. Current technologies allow to obtain the glasses with the absorption coefficient α=10-7 cm-1 at which the spectral resolution Δλ ≈10-2 pm could be reached. This is three orders of magnitude narrower than the resolution of existing acoustooptic AO filters with the same crystal thickness. The considered system (a Fabry-Perot spectral filter combining a Bragg grating mirrors with apodization) can significantly increase the resolution of optical diffraction filters. Complete elimination of sidelobes and a significant suppression of the “tails” of a diffraction reflection curve are demonstrated. These results open perspectives to significantly enhance the resolution of the spectrometers, improve the parameters of mobile devices and communication channels. The results are of practical interest and can be used in the development of new diffraction acousto-optic modulators, AO filters and spectrometers.
© (2020) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
N. I. Petrov and V. I. Pustovoit "Limit values of reflectivity of the periodic structure created by ultrasound in a crystal", Proc. SPIE 11516, Optical Technologies for Telecommunications 2019, 115160M (22 May 2020); https://doi.org/10.1117/12.2566345
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