Numerical Simulation of Grating Input/Output Elements into Optical Waveguides Based on Si3N4/SiO2 Thin Films

• Published in: 2023 IEEE 24th International Conference of Young Professionals in Electron Devices and Materials (EDM) pp. 860 - 863
• Main Authors: Barbin, Evgenij S., Kulinich, Ivan V., Koleda, Aleksej N., Myrzakhmetov, Ayan, Perin, Anton
• Format: Conference Proceeding
• Language: English
• Published: IEEE 29.06.2023
• Subjects: Diffraction; diffraction grating; Diffraction gratings; Etching; etching depth; filling factor; Geometrical optics; Gratings; input/output of optical radiation; insertion angle; Optical reflection; Optical variables control; period; silicon nitride; undercutting
• ISSN: 2325-419X
• DOI: 10.1109/EDM58354.2023.10225188

This paper presents the results of modeling a grating element for input/output of optical radiation into Si 3 N 4 /SiO 2 waveguide structures in the wavelength range from 1.5 to 1.6\ \mu \mathrm{m} . The results of the study of the geometric parameters of a diffraction grating on the optical transmission coefficient, in particular: the grating period, undercutting period, etching depth, filling factor, are presented. For a wavelength of 1.55\ \mu \mathrm{m} the maximum optical transmission coefficient is observed at: grating period 0.875\ \mu \mathrm{m} ; etching depth 0.181\ \mu \mathrm{m} ; fill factor of 0.595\ \mu \mathrm{m} ; undercutting \pm 0.015\ \mu \mathrm{m} . The greatest contribution to the change in the transmission coefficient is made by the change in the grating period and is \pm 0.0022\ \mu \mathrm{m}/{\%} and the etching depth is \pm 0.00762\ \mu \mathrm{m}/{\%} . Based on the results of simulations, taking into account the operating wavelengths and refractive indices of Si 3 N 4 /SiO 2 films, the following permissible deviations of diffraction lattice parameters were put forward: grating period \pm 0.022\ \mu \mathrm{m} ; etching depth \pm 0.0762\ \mu \mathrm{m} ; filling factor ±20%; undercutting period \pm 0.14\ \mu \mathrm{m} . Permissible insertion angles were 10-12 degrees. The reflection loss at the input of light into the waveguide was −17 dB, and at the output from −20 to −35 dB. Transmission loss at −3dB was 0.09\ \mu \mathrm{m} .