Strengthening of poly-crystalline (ceramic) Nd:YAG elements for high-power laser applications

In the last decade, poly-crystalline (ceramic) Nd:YAG components emerged as very promising candidates for high-power lasers, exhibiting some advantages over single-crystal Nd:YAG ones. Such devices are required to endure high thermal stress during operation. In our present work we present experimental results on the strengthening of poly-crystalline YAG and Nd:YAG fine-ground components by chemical etching in hot ortho-phosphoric acid. The strength of poly-crystalline Nd:YAG laser rods was measured inside a laser head by applying the pump power till rod fracture. A factor of ∼3 increase in the fracture longitudinal heat power density for etched poly-crystalline Nd:YAG rods as compared to standard commercial poly-crystalline rods was obtained. This effect is similar to our previous results on single-crystal Nd:YAG laser rods which showed a factor of 3.6–5.0 increase in tensile strength by the same treatment. A modified Weibull analysis was used to assess the fracture probability parameters.