A single-frequency, graphene-based passively Q-switched Tm : YAP laser

We report a single-frequency, passively Q-switched Tm : YAP laser using a volume Bragg grating (VBG) as the spectral selective element, and graphene as the saturable absorber (SA). A stable single-frequency pulse laser with line width of about 4.2 MHz at central wavelength of 1988.8 nm was obtained. The average output power of the single-frequency pulse laser was measured as 724 mW, corresponding to the single pulse energy of 7.5 μJ with the repetition rate of 96.2 kHz. This project provides a simplified and low-cost laser design to obtain single-frequency pulse laser by using VBG and graphene SA.