Compact Ho:YAP laser intra-cavity pumped by a Tm:YAP laser with identical crystallographic orientation

Intra-cavity pumped Ho laser basing on the biaxial YAP host is investigated here for a direct LD pumped compact polarized 2.1 μm laser at room temperature, where the a-cut and b-cut Tm:YAP and Ho:YAP crystals were applied and placed with the same crystallographic orientation. The maximum output power of 2.47 W at 2118 nm was obtained for the b-cut Ho:YAP laser with a slope efficiency of 15.1%, which is higher than that of 1.08 W at 2130 nm for the a-cut Ho:YAP laser with a slope efficiency of 8.9%, attributed to the better spectral overlap between the intra-cavity Tm laser and polarized absorption profile of the Ho:YAP crystal. Scaling up the output power and slope efficiency of the current Ho:YAP laser is predictable via improving heat management of the current structure further by diffusion bonding the Tm:YAP crystal with another un-doped YAP crystal or using a slab Tm:YAP crystal structure for rapid heat transfer.