Q-switched pulses amplified with short thulium-doped silicate fibers

Abstract

30ns, 3μJ Q-switched pulse laser with the repetition rate of 10 kHz at 1950 nm was amplified with a 50cm long piece of thulium(Tm)-doped silicate fiber, and 300μJ pulses with the pulse width of 20 ns were obtained. The heavily Tm-doped silicate fiber has the cladding-pump absorption of 22dB/m at 793nm and the fiber maintains solid single-mode operation at 1950nm. To further increase output pulse energy, the Q-switched seed was pre-amplified to 20 μJ with core-pumping at 1567 nm. The power amplifier features of a 55cm long piece of Tm-doped silicate fiber with 21μm core. ~600μJ pulses with peak power up to 28 kW have been achieved. The ASE was suppressed 40dB below the laser pulses due to the short highly Tm-doped silicate fiber. Mode-locked pulses with the pulse energy of 0.3 nJ and the spectral width of 14 nm were amplified with a 30cm long Tm-fiber with 10 μm core, pulses with 16kW peak power as well as 20nJ pulses were achieved. With another Tm-doped silicate fiber (22μm core), 36nJ pulses with 1.1ps pulse width were obtained in all-fiber configuration. The high peak power pulses at 2 μm reported here should be useful for mid-IR generation.