Refractive index matching cooling fluids for diode pump solid state lasers

Diode pump solid state lasers (DPSSLs) have been widely used in various fields such as material processing, the military, and medical and scientific research because of their high efficiency, long life, good beam quality, and compact structure. In this paper, a variety of refractive index matching cooling fluids was used in DPSSLs. Liquids examined include nontoxic and minimally toxic mineral oil (M98511), (KN-X (4006, 4010, 4016)), dialkyl ester compounds (B109815 and D109648), and chlorinated paraffin (041102-52). Their properties, including refractive index, temperature coefficient of the refractive index (DN/dt), dynamic viscosity, absorption coefficient, and thermal conductivity, were studied. The DN/dt of the matching liquid coolant was −3.6 × 10−4 to −3.9 × 10−4, and complete absorption at 808 ± 5 nm was better than 0.001%. Additionally, the best absorption coefficient at 1064 ± 5 nm reached 0.144%, which was much better than the Cargille samples 2.256%.