We present a gallium antimonide-based semiconductor saturable absorber mirror (SESAM) operating at 2 μm
wavelength region. GaSb-based material system is the preferred choice for fabricating surface-normal devices operating
beyond 2 μm because it enables the use of highly reflective semiconductor reflectors and quantum wells for wide
wavelength range. For the purpose of generating short laser pules, the SESAM was carefully designed to attain a large
modulation depth. The device was utilised successfully to passively Q-switch a 2 μm Tm<sup>3+</sup>-/Ho<sup>3+</sup> -doped fiber laser,
demonstrating record-short Q-switch pulses of about 20 ns.
We report tunable thulium/holmium-doped single mode fiber laser passively Q-switched by an antimonide-based
semiconductor saturable absorber mirror (SESAM) and boosted in Tm/Ho amplifier up to 2 W of average power. Pulse
operation tunable from 1960 nm to 1990 nm with pulse energies up to 30 μJ has been achieved. The study presents the
first demonstration of 2 μm Q-switched fiber laser using antimonide semiconductor technology.