Self-Injection Locked Silica External Cavity Narrow Linewidth Laser

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Abstract
A silica-based external cavity narrow linewidth laser is fabricated and experimentally demonstrated based on a commercial silica platform. An add-drop microring resonator and a 2×2 directional coupler in the silica chip form a wavelength-dependent and self-injection-locked external cavity. The linewidth-suppressing effect of the external cavity is theoretically calculated based on the chirp reduction theory, which shows that a long external cavity length at the resonant wavelength can be used to suppress the noise of a free-running laser. In the self-injection locked state, the measured intrinsic linewidth of the fabricated external cavity laser is 27 Hz, which is greatly reduced compared to the 49.7-kHz linewidth of the free-running state. The frequency stability is also measured to be improved by an order of magnitude from 4.52 × 10 −8 to 9.07 × 10 −10 at 1 s averaging time. The proposed narrow-linewidth laser shows the potential for massive production and can be used in various applications such as integrated microwave photonics, LIDAR, high-resolution metrology, and satellite communications.
Funding Information
  • National Key Research and Development Program of China (2019YFB2203200)
  • National Natural Science Foundation of China (61925505, 62135014, 62001043)
  • Beijing Natural Science Foundation (Z210005)
  • Chinese Academy of Sciences through Strategic Priority Research Program (XDB43030200, XDB43030000)
  • Chinese Academy of Sciences through Key Research Program (ZDRW-XX-2022-3, ZDRW-XX-2022-3-1)

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