A generation of 2 μm Q-switched thulium-doped fibre laser based on anatase titanium(IV) oxide film saturable absorber

Abstract

We demonstrate a Q-switched thulium-doped fibre laser operating at approximately 1935 nm wavelength using anatase titanium(IV) oxide (TiO2) embedded in polyvinyl alcohol as the passive newly saturable absorber (SA). The film has absorption loss of 3.5 dB and modulation depth of 33%. It is sandwiched between two fibre ferrules in a ring laser cavity to produce self-started pulse train with a repetition rate that is tuned from 30.12 to 36.96 kHz as the 1552-nm pump power is increased from 289 to 485 mW. At maximum pump power, the laser produced a Q-switching pulse train with pulse duration, output power, pulse energy and peak power of 1.91 μs, 11 mW, 0.3 μJ and 146 mW, respectively. These results show that the TiO2 is a new potential SA material for pulsed laser applications.