Passively Q-switching in the direct AlGaAs LD pumped Tm/Ho composite laser

We demonstrate passively Q-switching in a 2.1 μm Tm/Ho composite laser via developing a hybrid cavity to separate the intra-cavity Tm laser from modulated by the saturable absorber (SA). Enhancement in Ho laser efficiency was demonstrated in the proposed hybrid cavity, compared with the common two-mirror laser resonator. Using the crystalline Cr:ZnSe SA, maximum average output power of 553 mW at 2090 nm under absorbed 808 nm LD power of 6 W was obtained at pulse repetition rate of 9.5 kHz. Using layered WSe2 SA fabricated with the CVD process, maximum Ho laser power of 141 mW with pulse width of 185 ns at a repetition rate of 33 kHz was obtained. The current gain medium could be replaced with other hosts such as YVO4, YLF, and YAP with natural birefringence, which facilities a potential polarized pulse Ho laser. Also, the current SAs could also be replaced by other nanomaterials with controllable broadband saturable absorption such as gold nanorods,topological insulators and carbon nano tube for seeking novel pulse Ho lasers.