Grating Coupler Design for Vertical Light Coupling in Silicon Thin Films on Lithium Niobate

Huangpu Han,Bingxi Xiang

doi:10.3390/cryst10090850

Abstract

In this paper we provide a design for a vertical grating coupler for a silicon thin film on lithium niobate. The parameters-such as the cladding layer thickness of lithium niobate, fiber position, fiber angle, grating period, and duty cycle are analyzed and optimized to reduce the mode mismatch loss and the internal reflections. The alignment tolerances, for the grating coupler parameters, are also simulated and evaluated. We determine that our simulated grating coupler exhibits high efficiency, enhanced light coupling, and high alignment tolerance.

Highlights

In dense photonic integration, highly developed silicon (Si) platforms have attained numerous substantial successes
An alternative is lithium niobate (LiNbO3, LN) crystal, which is more promising in this role [2,3,4] because of its wide transparency range and excellent electro-optic, nonlinear, acousto-optic, piezoelectric, photorefractive, and elasto-optic properties
Contrary to photonics based on Si, the manufacturing of LN photonic devices is still in its infancy

Summary

Introduction

Highly developed silicon (Si) platforms have attained numerous substantial successes. The advantages of this mature technology are their low optical absorption, large refractive index contrast, and high compatibility with semiconductor technology [1]. Single-crystal Si is a centrally symmetric crystal that has no linear electro-optic effect, piezo-electric or other similar properties. The Si material has limitations in its application to integrated optics. An alternative is lithium niobate (LiNbO3 , LN) crystal, which is more promising in this role [2,3,4] because of its wide transparency range and excellent electro-optic, nonlinear, acousto-optic, piezoelectric, photorefractive, and elasto-optic properties.

Methods

Discussion

Conclusion