Single-mode characteristic of a supermode microcavity Raman laser

Creators: Zhang, Pei-Ji; Ji, Qing-Xin; Cao, Qi-Tao; Wang, Heming; Liu, Wenjing; Gong, Qihuang; Xiao, Yun-Feng

Abstract

Microlasers in near-degenerate supermodes lay the cornerstone for studies of non-Hermitian physics, novel light sources, and advanced sensors. Recent experiments of the stimulated scattering in supermode microcavities reported beating phenomena, interpreted as dual-mode lasing, which, however, contradicts their single-mode nature due to the clamped pump field. Here, we investigate the supermode Raman laser in a whispering-gallery microcavity and demonstrate experimentally its single-mode lasing behavior with a side-mode suppression ratio (SMSR) up to 37 dB, despite the emergence of near-degenerate supermodes by the backscattering between counterpropagating waves. Moreover, the beating signal is recognized as the transient interference during the switching process between the two supermode lasers. Self-injection is exploited to manipulate the lasing supermodes, where the SMSR is further improved by 15 dB and the laser linewidth is below 100 Hz.

Additional Information

© 2021 the Author(s). Published by PNAS. This open access article is distributed under Creative Commons Attribution License 4.0 (CC BY). Edited by Alexis T. Bell, University of California, Berkeley, CA, and approved April 29, 2021 (received for review January 27, 2021). We thank X.-C. Yu, J.-H. Chen, Q.-F. Yang, and Y.-Z. Gu for helpful discussions, as well as S.-J. Tang and Y. Zhi for comments on the manuscript. This project is supported by the National Natural Science Foundation of China (Grants 12041602, 11825402, 11654003, 61435001, 11527901, and 62035017), the National Key R&D Program of China (Grants 2018YFB2200401 and 2016YFA0301302), the Key R&D Program of Guangdong Province (2018B030329001), the National Postdoctoral Program for Innovative Talents (Grant BX20200014), and the China Postdoctoral Science Foundation (Grant 2020M680185). Data Availability: All study data are included in this article. P.-J.Z. and Q.-X.J. contributed equally to this work. Author contributions: P.-J.Z., Q.-X.J., and Q.-T.C. performed the experiments; P.-J.Z., Q.-X.J., Q.-T.C., and H.W. proposed the theoretical model; P.-J.Z., Q.-X.J., Q.-T.C., H.W., W.L., Q.G., and Y.-F.X. analyzed data; P.-J.Z., Q.-X.J., Q.-T.C., H.W., W.L., Q.G., and Y.-F.X. wrote the paper; Q.-T.C. and Y.-F.X. conceived the idea; and Q.G. and Y.-F.X. supervised the project. The authors declare no competing interest. This article is a PNAS Direct Submission.

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