Layered WSe2 Q-witched Tm/Ho composite laser in a resonance-enhanced hybrid cavity

Layered WSe2 membrane prepared via chemical vapor deposition was used as the saturable absorber (SA) for seeking Q-switching in a direct 808 nm LD pumped Tm/Ho composite laser. For separating the Tm laser from modulated by the SA which leads to the failure in Q-switching, a spectral filter was inserted intra-cavity to form a hybrid cavity, where resonance enhancement in the Ho laser compared with using the conventional cavity was observed. Successful Q-switching with maximum average output power of 141 mW at 2090 nm was obtained under output coupling of 2%, where the shortest pulse width was 185 ns at repetition rate of 33 kHz, corresponding to a pulse energy of 4.36 µJ and peak power of 23.1 W. It is the first presentation of 2D material applied in the Tm/Ho composite laser at 2.1 µm, where the current SA could be replaced by other pulse modulation materials such as topological insulator, graphene, or golden nano-rod for seeking novel pulse Ho lasers.