Suppression of Back-Reflection From the End Face of Si3N4 Waveguide Resonator

Changkun Feng,Peiren Ni,Lishuang Feng,Hui Li,Danni Liu

doi:10.1109/access.2021.3059746

Abstract

Silicon nitride waveguide (Si3N4), is used as the most important sensitive device because of its excellent high-polarizing characteristics. It has the potential to build the miniaturized, high-precision resonant integrated optical gyroscope (RIOG) in recent years. However, the back-reflection caused by the refractive index difference between the Si3N4 waveguide and the pigtail fiber has a non-negligible impact on the accuracy of the gyroscope. In this paper, we propose a method to suppress the back-reflection of the end face of the Si3N4 waveguide resonator. We use the Fimmprop module of the simulation software Photon Design to simulate the relationship between the back-reflection coefficient of Si3N4 waveguide and different tilt angles. The simulation result shows that when the end face of the Si3N4 waveguide is oblique cut by 15°, the back-reflection is the minimum, about −67 dB. The back-reflection obtained through the experiments are about −65 dB, consistent with the simulation result. Together, our data suggested that the back-reflection noise of the Si3N4 can be suppressed by the oblique cutting of the end face by 15°. The conclusion can lay a foundation for improving the performance of RIOG based on Si3N4 waveguide resonator.

Highlights

The optical gyroscope is a type of optical sensor used to measure the rotational angular velocity based on the optical Sagnac effect [1]-[6]
It is mainly composed of a laser, an erbium doped optical fiber amplifier (EDFA), two optical isolators (ISO), an optical circulator (OC), the Si3N4 waveguide and optical power meter
The Si3N4 waveguides have excellent high polarization, so the resonant integrated optical gyroscope (RIOG) based on Si3N4 waveguide resonators have received more attention currently

Summary

INTRODUCTION

The optical gyroscope is a type of optical sensor used to measure the rotational angular velocity based on the optical Sagnac effect [1]-[6]. The fluctuation supports the simultaneous transmission of two polarization states in the waveguide resonator, and cause the energy coupling between the primary (i.e. TE mode) and secondary polarization states (i.e. TM mode) to rapidly deteriorate the performance of the gyroscope This is the most important factor affecting longterm stability of RIOG and limits its performance. There are few reports on RIOG based on Si3N4 waveguide resonators, and no studies are on methods to suppress the back-reflection noise caused by the end faces of Si3N4 from the Si3N4 waveguide resonator itself. The end face of the Si3N4 waveguide resonator is oblique cut to suppress the back-reflection noise caused by the waveguide end faces. During the transmission of the back-reflection light, it passes through the transmission end, and its electric field amplitude transfer function is: i

C1 1 kC1

BACK-REFLECTION SUPPRESSION METHOD

EXPERIMENTAL RESULTS

DISCUSSIONS

CONCLUSIONS