Gain-Switched Single-Frequency DBR Pulsed Fiber Laser at 2.0 μm

A gain-switched single-frequency distributed Bragg reflector (DBR) Tm
$^{3+}$
-doped fiber pulsed laser operating at 1950 nm is demonstrated experimentally. The gain-switched process is realized by in-band pumping a DBR ultra-short linear cavity via a 1610 nm pulsed fiber laser (pump source). Driven by this pump with varying modulation frequency, repetition rate of the laser output can be flexibly tuned from 1 to 500 kHz. As a result, a maximum peak power of 34.2 W is achieved with a repetition rate of 100 kHz and a pulse width of 19 ns. Moreover, the generated pulses at
$2.0~\mu \text{m}$
have excellent optical signal-to-noise ratio of >65 dB and exhibit stable single-longitudinal-mode status throughout the experiment. To the best of our knowledge, this is the first demonstration of
$2.0~\mu \text{m}$
gain-switched single-frequency pulsed fiber laser based on Tm
$^{3+}$
-doped fiber, showing great potential for applications including medical treatment, nonlinear frequency conversion and coherent Doppler lidar.