基于高Q值Si3N4片上光学微腔的孤子光频梳

Single soliton microcomb based on high-Q on-chip Si3N4 optical micro-resonators

摘要:

高Q值片上微腔已被证明是一个优秀的克尔孤子光学频率梳产生平台。由片上多模波导构成的Si3N4微腔可以同时实现产生暗孤子所必须的高品质因子和反常色散。为了进一步降低产生单孤子光频梳的阈值功率,本文设计了一种具有欧拉弯曲的新型跑道型Si3N4微腔,与传统的圆形弯曲波导相比,跑道型微腔直波导连接处弯曲半径的突然变化被显著抑制,这抑制了高阶模式耦合并降低了传播损耗,从而获得了超过5×106^的品质因子。基于该新型微腔,使用辅助激光加热方法仅用47mW泵浦激光器(估计片上泵浦功率33mW)就产生了重复频率在Ka波段且带宽超过20nm(对应于129fs的脉冲持续时间)的单孤子微腔光频梳。本文为高Q值片上光学微腔的设计提供了新的思路。

Abstract:

High-Q on-chip micro-resonators has been proved to be a promising platform for Kerr soliton frequency comb generation. Si3N4 micro-resonators composed of multi-mode waveguides can achieve high quality factor and anomalous dispersion, which are necessary for soliton generation. To further reducing the threshold power for generating single soliton microcomb, a novel racetrack Si3N4 micro-resonator with Euler bends is reported, which achieved loaded Q factors of more than 5×10⁶. Compare to conventional circular bends, the sudden change in bending radius at the waveguide connection is significantly suppressed, which suppresses mode interaction and reduces propagation loss. With this novel micro-resonator, single soliton frequency combs with a repetition rate in the microwave Ka band and a bandwidth of over 20nm (corresponding to a pulse duration of 129fs) is generated with only a 47mW pump laser (33mW estimated on-chip pump power) using the auxiliary laser heating method.