High external power narrow bandwidth erbium doped waveguide laser on thin film lithium niobate

Erbium-doped waveguide lasers have attracted great interests in recent years due to their compact footprint, high scalability and low phase noise. In this work, by using a high-external-gain erbium-doped thin-film lithium niobate waveguide as the gain medium, a fiber-Bragg-grating based Fabry–Perot-type laser is demonstrated with the low pump threshold of few-milliwatts, narrow bandwidth of 0.1 nm, high external output power above 2 mW and maximum optical signal-to-noise ratios above 50 dB. Laser linewidth measurements by self-delayed homodyne and heterodyne detections reveal the underlying multi-longitudinal-mode laser structure and the average intrinsic linewidth as low as ∼50 kHz for the individual longitudinal-modes. Theoretical modeling of the waveguide laser is also conducted with high consistence with the experimental measurements. The demonstrated high-power erbium-doped waveguide laser on thin-film lithium niobate can find diverse applications in optical communication and laser sensing.