Physical vapor deposition of large-scale PbSe films and its applications in pulsed fiber lasers

Lead selenide (PbSe) is a new emerging semiconductor with layer-dependent bandgap that has attracted much interest due to its high infrared response and good environmental stability. We have prepared large-scale PbSe films with the area of 7 cm2 and thickness of 25 nm based on physical vapor deposition approach at 160°C. The PbSe films exhibit saturable absorption property at 1.55 μm and a polarization-sensitive saturable absorber is obtained by growing PbSe on D-shaped fiber. Single-pulse with the duration of 490 fs is generated at the pump of 12 mW and the mode-locking operation is maintained at the pump of 1500 mW, indicating the high damage threshold of the D-shaped fiber based saturable absorber. Two polarization-insensitive saturable absorbers are achieved by depositing PbSe on fiber facet and polyvinyl alcohol film, respectively. For fiber facet (polyvinyl alcohol film) based saturable absorber, the repetition rate of Q-switched pulses increases from 8.6 (16.3) kHz to 45.4 (59.2) kHz while the duration decreases from 7.92 (12) μs to 2.06 (3.12) μs by tuning the pump from 15 mW to 90 (60) mW. Such large-scale PbSe films possess features of low cost and high modulation ability, and can find important applications in infrared optical modulators and detectors.