• Chinese Optics Letters
  • Vol. 20, Issue 3, 032201 (2022)
Shuai Wan1、2, Rui Niu1、2, Jin-Lan Peng3, Jin Li1、2, Guang-Can Guo1、2, Chang-Ling Zou1、2, and Chun-Hua Dong1、2、*
Author Affiliations
  • 1CAS Key Laboratory of Quantum Information, University of Science and Technology of China, Hefei 230026, China
  • 2CAS Center For Excellence in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei 230026, China
  • 3Center for Micro and Nanoscale Research and Fabrication, University of Science and Technology of China, Chinese Academy of Sciences, Hefei 230026, China
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    The microresonator-based soliton microcomb has shown a promising future in many applications. In this work, we report the fabrication of high quality (Q) Si3N4 microring resonators for soliton microcomb generation. By developing the fabrication process with crack isolation trenches and annealing, we can deposit thick stoichiometric Si3N4 film of 800 nm without cracks in the central area. The highest intrinsic Q of the Si3N4 microring obtained in our experiments is about 6×106, corresponding to a propagation loss as low as 0.058 dBm/cm. With such a high Q film, we fabricate microrings with the anomalous dispersion and demonstrate the generation of soliton microcombs with 100 mW on-chip pump power, with an optical parametric oscillation threshold of only 13.4 mW. Our Si3N4 integrated chip provides an ideal platform for researches and applications of nonlinear photonics and integrated photonics.

    1. Introduction

    The optical frequency comb, which is a series of equidistant coherent optical lines in the frequency domain, has been greatly developed in the past two decades[13]. The conventional optical frequency comb is produced by the mode-locked laser and has played an important role in the precise measurement of time and frequency[46]. Based on the optical field enhancement of the microresonator, in 2007, the generation of the optical frequency comb was realized in the microresonator by continuous-wave (CW) laser pumping[7], which opens a new field of optical frequency combs based on the microresonator. Due to the emergence of noise in the generation process[8], the early microresonator frequency combs showed low coherence, and their application value was not expected. In recent years, with the discovery of dissipative Kerr solitons[9], stable and fully coherent soliton microcombs can be obtained in microresonators by simultaneously balancing gain and loss, as well as dispersion and nonlinearity[1013].