Narrow-linewidth hybrid waveguide/fiber laser at 1535 nm

A hybrid waveguide/fiber laser in single-frequency operation is demonstrated for the first time to the best of our knowledge. A resonant ring, which is used as a filter in the laser cavity to select a single longitudinal mode based on the multiple-beam interference effect, is fabricated in a SiO2-based waveguide. The resonant ring presents strong mode selection ability, by significantly increasing the loss difference between the main oscillating mode and the side modes. During the experiment, a hybrid waveguide/fiber laser is constructed with a 10 mm diameter resonant ring. The single-frequency output power of the laser is 3.5 mW at 1535 nm. The linewidth is measured to be less than 800 Hz by the delayed self-heterodyne method.