Multi-Wavelength, Passively Q-Switched, Single-Frequency Fiber Laser

A passively Q-switched single-frequency fiber laser with stable multi-wavelength operation is presented in this report. The laser cavity is constructed by using a 13-mm Er
³⁺
/Yb
³⁺
co-doped phosphate fiber with a multi-channel fiber Bragg grating and a semiconductor saturable absorber mirror attached to each fiber end, respectively. Quad-wavelength pulsed lasers are obtained and all of them maintain single-frequency operation. By controlling the pump power and the temperature of laser cavity, the Q-switched pulse operation is realized with repetition rates range of 126.6–350.9 kHz, a narrowest pulse duration of 104 ns, and a maximum pulse energy of 55.4 nJ. To the best of our knowledge, this is the first study to realize a Q-switched fiber laser operating at multiple wavelengths with single longitudinal mode. Furthermore, the evolutions of the pulse energy and repetition rates for different wavelength numbers are further analysis theoretically. This type of single-frequency pulsed fiber laser has extensive application prospect in fiber sensing and lidar systems.