Thermal lens effect induced in a Cr,Tm,Ho:YAG laser rod: A comparison between under lasing and non-lasing conditions

• The thermal lens of a CTH:YAG rod in the lasing and non-lasing regimes was measured. • For a more accurate resonator design, the lasing condition results should be considered. • Different results in the lasing regime may be caused by excited state absorption and up-conversion. In this paper, transient thermal lensing effects in a typical flashlamp-pumped CTH:YAG laser crystal under lasing and non-lasing conditions are studied and compared in a low repetition-rate regime. It is shown that in the lasing regime (for pumping energies higher than 90 J ) the time-resolved behavior and the strength of the three mode thermal lenses of the rod are different from the non-lasing condition. According to this research, it can be referred that higher-order processes such as excited state absorption of both pump and laser radiation and energy transfer up-conversion may have a more significant contribution to the laser dynamics in the lasing regime. The analysis of the results also shows that the energy transfer between different manifolds in Cr 3+ , Tm 3+ , and Ho 3+ ions may depend on coolant temperature.