A novel laser gain medium: Micro-sphere array cooled by refractive index-matched coolant

A micro-sphere array laser gain medium cooled by refractive index-matched coolant was demonstrated for the first time to our knowledge. The new concept is possessed of potential to improve thermal management, to increase the thermal load capacity and to build large scale laser medium with small-sized solid laser materials. The feasibility was experimentally proved with an oscillator experiment in which reliable laser output was observed: the maximum output was 113.3 mJ for the pump energy of 765.8 mJ, the threshold was 131.7 mJ and the slope efficiency was 19%. Promising improvement could be achieved by employing methods for maintaining accurate refractive index matching during the lasing process.