Yung-Sheng HUANG^* and Fang-Ling CHANG¹

Department of Electrical Engineering of I-Shou University, Kaohsiung county, 840, Taiwan
¹National Space Program Office, National Science Council, Hsinchu, 300, Taiwan

(Received March 8, 2005; Accepted July 20, 2005)

Our theoretical analysis showed that the overall intracavity frequency-doubled actively Q-switched solid state laser performance is affected by both pulse repetition rate and energy transfer up-conversion effect. The energy transfer up-conversion effect increased greatly and seriously degraded the laser performance especially when operating at high pumping power and low pulse repetition rate. The curves generated by numerical computation of the presented model can be used to predict the laser performance. We concluded that the pulse lengthening effect also appears with the influence of energy transfer up-conversion and is not related to the repetition rate. From the analysis, we found that the frequency doubling coefficient that Liu and Kim chose in their experiment was just the optimized value. Considering the effect of excited state absorption of saturable absorber into passively Q-switched intracavity frequency doubled solid state laser, the second threshold condition for this model is derived. A simple and very clear formula is obtained.

Key words: solid state laser, repetition rate dependence, intracavity frequency doubled, energy transfer up-conversion (ETU), second threshold condition, saturable absorber, initial transmission, excited state absorption (ESA)

^*E-mail address: yshuang@isu.edu.tw