Edge couplers in photonic integrated circuits based on thin-film lithium niobate

Koryagin V.A., Shabalin R.R., Moskalev D.N., Salgaeva U.O., Krishtop, V.М.

For Russian citation (Opticheskii Zhurnal):

Корягин В.А., Шабалин Р.Р., Москалев Д.Н., Салгаева У.О., Криштоп В.В. Элементы ввода излучения в фотонные интегральные схемы на основе тонкоплёночного ниобата лития // Оптический журнал. 2026. Т. 93. № 10. С. 67–74. http://doi.org/10.17586/1023-50862026-93-10-67-74

Koryagin V.A., Shabalin R.R., Moskalev D.N., Salgaeva U.O., Krishtop V.V. Edge couplers in photonic integrated circuits based on thin-film lithium niobate [in Russian] // Opticheskii Zhurnal. 2026. V. 93. № 10. P. 67–74. http://doi.org/10.17586/1023-5086-2026-93-10-67-74

For citation (Journal of Optical Technology):

Abstract:

Subject of study. This study evaluates the оptical coupling losses into integrated optical waveguides of a photonic integrated circuit based on thin-film lithium niobate using different types of mode field converters: inverted and linear tapers. Aim of study. The work aims to determine the type and topology of a mode field converter that provides the highest efficiency of butt-coupling into the channel integrated optical waveguide based on X-cut of thin-film lithium niobate. Method. The mode field distribution at the output of mode field converters of different sizes was modeled using the finite difference method in the frequency domain in Difra software. To evaluate the buttcoupling efficiency, the scalar overlap integral was calculated. Main results. Mode field converter topologies were developed, optical coupling losses were estimated, and variations in optical loss were analyzed depending on the optical fiber offset relative to the converter center. It was found that the lowest losses are observed when light is coupled through a linear taper (7.35 dB for TE polarization and 6.84 dB for TM polarization). Practical significance. Reducing the coupling losses in photonic integrated circuits improves device efficiency.

Keywords:

input efficiency, waveguide, lithium thin-film niobate, optical losses, mode field converters

OCIS codes: 130.1750, 130.3730, 250.5300

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