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 Microresonators

摘要:

高Q值片上微腔已被证明是一种性能优异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,文章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(估计片上泵浦功率为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。

Abstract:

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