We firstly demonstrated an obtainable Ho:YAP laser intra-cavity pumped by a diode-pumped Tm:YAP laser. A common 792 nm AlGaAs fiber coupled laser diode was used to pump the a-cut Tm:YAP crystal. In the Tm laser experiment, a maximum output power of 1.9 W at 1958.4 nm was obtained, corresponding to a slope efficiency of 12.1 %. In the Ho laser experiment, a maximum output power of 1.1 W at 2118.2 nm was obtained with a slope efficiency of 8.9% for 21.9 W diode incident pump power on the Tm:YAP crystal. At the maximum output power of the Ho laser, beam quality factor (M2) was measured to be 1.79 and 1.72 in the horizontal and vertical directions, respectively. Further improvement in the performances of the current Ho:YAP laser is predictable via direct producing a more compact gain module by adhesive-free bonding of Ho:YAP to Tm:YAP crystals.
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.
We developed a compact 2-μm intracavity-pumped Ho : YVO4 laser using a diode-pumped Tm:YAP laser at room temperature. Before applying the Ho laser, the lasing characteristics of the a-cut Tm:YAP laser were studied, and a maximum output power of 2.76 W at 1951.6 nm was obtained under an incident laser diode pump power of 25 W with a slope efficiency of 15.8%. Under the same cavity structure, the continuous-wave Ho : YVO4 laser yielded a maximum output power of 1.7 W at 2052.7 nm for an incident diode pump power of 29 W, corresponding to a slope efficiency of 10.4%. The beam quality factor (M2) of the Ho : YVO4 laser at the maximum output power was estimated to be 1.16 and 1.26 in the horizontal and vertical directions, respectively, which indicates the occurrence of near-diffraction-limited beam propagation.
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