Composite laser devices of passively Q-switched Nd:YAG were prepared by optical contacting of a Ca,Cr:YAG crystal onto a Nd:YAG wafer, followed by thermal treatments at elevated temperatures. Thermal treatments of the composite devices under reducing and/or oxidizing environments enabled to control the Cr4+ ion concentration, which affects its absorption saturation behavior. Optical absorption saturation measurements on partialy reduced Ca,Cr:YAG crystal revealed that residual absorption of the saturable absorber at 1064 nm results from excited-state absorption. Laser damage measurements at the gain/absorber interface of the monolithic device showed that the damage threshold at the gain/absorber interface of the composite device is higher than at the entrance interface. The high optical quality device thus obtained was end-pumped by a fiber-optic-coupled diode laser, and exhibited a high repetition-rate oscillations of short pulses, with fair beam quality.
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