2 μm band pulsed all-PM thulium-doped fiber laser based on the acousto-optic Q-switching

We report a 2 μm band high power pulsed all-polarization maintaining (PM) thulium-doped fiber laser based on the acousto-optic q-switching technique. It is constructed in a two-stage master-oscillator power amplifier (MOPA) configuration. A Q-switched seed laser was composed of a homemade 1559 nm fiber laser, a pair of fiber Bragg gratings (FBGs) with central wavelength at 2009 nm, a piece of single-cladding thulium-doped fiber (TDF) and an acoustic-optical modulator (AOM). Using a two-stage amplifier seeded by an acousto-optic modulator modulated pulsed laser, We achieved the laser with a central wavelength of 2009.71 nm, and the laser has a 3 dB linewidth of 0.09nm and output power of approximately 2.04 W. Based on the acousto-optic switch, the pulse width of 97 ns at a repetition rate of 20 kHz was obtained. The maximum peak-power of the fiber power amplifier is 2.1 kW and pulse energy is more than 204 μJ. This high power thulium-doped fiber laser has an all-fiber based configuration. We used a cladding power stripper (CPS) with matched passive fiber to remove residual pump light that leaked into cladding. The slope efficiency of the thulium-doped fiber power amplifier was 22.7%.