Comparison of laser induced thermal fracture between polycrystalline ceramic and crystal Nd:YAG.

Continuous wave 808 nm pump laser-induced thermal damage of polycrystalline transparent ceramic and crystalline Nd:YAG materials was investigated both experimentally and theoretically. The measured temperature agrees well with the theoretical simulation, and the maximum hoop stresses occur on the incident facet of the end-pumped rod at about √2 times of the pump beam radius w0, where the temperature gradient is the highest and the damage occurs first at this location. The fracture-limited laser intensity of ceramics was experimentally measured to be 6.4±0.6  kW/cm2, nearly 64% higher than that of the crystals (3.9±0.3  kW/cm2). The deduced thermal fracture stress for ceramic was 386±50  MPa, which is 64% higher than that of the crystals (235±16  MPa).