Monolithic Single-frequency Laser On Thin-film Lithium Niobate Platform by The Vernier Effect

We present a monolithic single-frequency microring laser utilizing Er³⁺-doped thin film lithium niobate (TFLN) on insulator. The device is fabricated employing a dual-cavity architecture, in which two microring resonators are nested through two pulley coupling regions and share a common semicircular cavity. The single-frequency laser achieves a peak output power of 146 μW, with a side mode suppression ratio (SMSR) of 32 dB and slope efficiency of 0.7%, operating at a wavelength of 1530.85 nm, which leverage gain competition and the Vernier effect. Furthermore, the single-frequency laser emission can be selectively switched between 1530.85 nm and 1547.13 nm by a precise adjustment of the device's structural parameters. Our research establishes the foundation for a fully integrated multifunction TFLN system, which exhibit great potential applications in advancing optical computation, bio-chemical sensing and signal processing.