Stimulated Raman scattering is an attractive way to extend the operation spectral range of optical sources. However, the spectral extension range of a tunable Raman laser is limited by the Raman frequency shift and pump tuning bandwidth. This makes it challenging to realize chip-scale, widely tunable Raman lasers, as on-chip lasers only provide limited pump power and tuning bandwidth. Here, we tackle this by dispersion engineering of a thin-film lithium niobate microring resonator, where its high-quality factor ( ~ 2.5 million) ensures a sub-milli-watt (0.8 mW) threshold for Raman lasing while its strong normal dispersion with suppressed avoided mode crossing restrains the competing Kerr comb generation process. Combining the multi-wavelength Raman gain response of lithium niobate and cascaded Raman lasing, we demonstrate a widely tunable Raman laser covering 1592–1955 nm, showing a 335-nm spectral extension range from a 94-nm-tuning-bandwidth pump laser. Our demonstration paves the way to realize chip-scale, widely-tunable Raman lasers.

受激拉曼散射是扩展光源工作光谱范围的一种有吸引力的方法。然而，可调谐拉曼激光器的光谱扩展范围受到拉曼频移和泵浦调谐带宽的限制。这使得实现芯片级、广泛可调的拉曼激光器具有挑战性，因为片上激光器仅提供有限的泵浦功率和调谐带宽。在这里，我们通过薄膜铌酸锂微环谐振器的色散工程来解决这个问题，其高质量因数（约 250 万）确保拉曼激光的亚毫瓦（0.8 mW）阈值，同时其强大的法向色散抑制避免模式交叉抑制竞争克尔梳生成过程。结合铌酸锂的多波长拉曼增益响应和级联拉曼激光，我们展示了一种覆盖 1592-1955 nm 的宽可调拉曼激光器，显示了 94 nm 调谐带宽泵浦激光器的 335 nm 光谱扩展范围。我们的演示为实现芯片级、广泛可调的拉曼激光器铺平了道路。