Passively Q-Switched Thulium-Doped Fiber Laser Employing a Glycerin-Based Saturable Absorber

A passively Q-switched Thulium-doped fiber laser based on glycerin as the saturable absorber is experimentally demonstrated for the first time. The saturable absorber consists of two FC/PC connectors aligned within a mechanical fiber-fiber coupler, with the intervening gap filled with glycerin. Such a saturable absorber is integrated into a compact ring cavity, enabling passive Q-switched laser operation. Starting at a minimum pump power of 1.7 W, Q-switched pulses with a central wavelength of 1946 nm are obtained. At the maximum pump power of 2.4 W, the laser generates pulses with a duration of approximately 2 µs, a repetition rate of 26.7 kHz, and a pulse energy of 1.08 µJ. To the best of our knowledge, this is the first demonstration of passively Q-switched laser operation utilizing a glycerin-based saturable absorber for generating pulsed emission at the 2-µm wavelength region. This breakthrough represents a significant advancement in fiber laser technology, introducing a novel and efficient approach to pulse generation.