Theoretical and Experimental Study on High Peak Power Sub-Nanosecond Pulse Characteristics of Multi-Segment Composite Nd:YVO 4 Laser

By simultaneously employing electro-optic modulator and GaAs, the dual-loss-modulated Q-switched and mode-locked sub-nanosecond laser of the multi-segment composite Nd:YVO 4 /Nd:YVO 4 /Nd:YVO 4 crystal was investigated for the first time. The threshold pump power for obtaining the single mode-locking sub-nanosecond pulses was 5.72 W. When the incident pump power was 8.76 W, the maximal average output power of 885 mW and the shortest pulse duration of 489 ps were generated at 1 kHz repetition rate, corresponding to the highest peak power of 1.8 MW. Compared with the conventional Nd:YVO 4 crystal, the multi-segment composite one depicted better thermomechanical performance and obtained much higher peak power. Coupled rate equations are brought in to theoretically analyze the experimental results, in which a hyperbolic secant square function and the Gaussian distribution of the intracavity photon density are considered. The simulated calculations are in accordance with the experimental results.