Pockels soliton microcomb

• Published in: Nature photonics Vol. 15; no. 1; pp. 21 - 27
• Main Authors: Bruch, Alexander W., Liu, Xianwen, Gong, Zheng, Surya, Joshua B., Li, Ming, Zou, Chang-Ling, Tang, Hong X.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01.01.2021; Nature Publishing Group
• Subjects: 639/624; 639/624/400; 639/624/400/1021; 639/624/400/1118; 639/624/400/385; Aluminum; Aluminum nitride; Applied and Technical Physics; Nonlinear systems; Nonlinearity; Optical frequency; Photonic crystals; Physics; Physics and Astronomy; Quantum Physics; Resonators; Solitary waves; Three-wave mixing
• ISSN: 1749-4885; 1749-4893
• DOI: 10.1038/s41566-020-00704-8

Kerr soliton microcombs have recently emerged as a prominent topic in integrated photonics and have enabled new horizons for optical frequency metrology. Kerr soliton microcombs, as the name suggests, are based on high-order cubic optical nonlinearity. It is desirable to exploit quadratic photonic materials, namely Pockels materials, for soliton generation and on-chip implementation of 1 f –2 f comb self-referencing. Such quadratically driven solitons have been proposed theoretically, but have not yet been observed in a nanophotonic platform, despite recent progress in quadratic comb generation in free-space and crystalline resonators. Here, we report photonic-chip-based Pockels microcomb solitons driven by three-wave mixing in an aluminium nitride microring resonator. In contrast to typical Kerr solitons, the Pockels soliton features unity soliton generation fidelity, two-by-two evolution of multi-soliton states, favourable tuning dynamics and high pump-to-soliton conversion efficiency. Photonic-chip-based microcomb solitons driven by Pockels nonlinearity—the quadratic χ (2) effect—instead of the Kerr soliton are demonstrated in an aluminium nitride microring resonator with a conversion efficiency of 17%.