Quantitative measurement of thermal lens in diode-laser pumped self-frequency-doubled Nd,Lu : YAl3(BO3)(4) laser under lasing and non-lasing conditions

We present a quantitative comparison between thermal lenses under lasing an d non-lasing conditions in a diode-laser pumped self-frequency-doubled Nd,L u:YAl3(BO3)(4) laser using an interferometric technique. At the pump power of 1.5 W, the thermal lens under the non-lasing condition attained 8 m(-1), and this corresponded to 170% of that under the lasing condition. Validity of the measured thermal lenses was confirmed by investigating the dependen ce of output power on the cavity length. The difference between thermal len ses under lasing and non-lasing conditions is caused by the nonradiative lo ss process of the upper level due to the cross-relaxation.