Combined actively and passively Q-switched microchip laser

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Until now active or passive Q-switching have been used to achieve highly energetic laser pulses. Both these pulsing techniques have advantages as well as drawbacks. Passive Q- switching is extremely simple and need no electronic driving, but the emitted pulse has a large time jitter (100 ns to 1 ms) between the emitted pulses, which is detrimental in many applications. Active Q-switching on the other hand require advanced high voltage drive electronics which consume a substantial amount of electrical power, but the emitted pulse train is normally clean and well-behaved. In this paper we propose and demonstrate a novel Q-switched diode-pumped solid- state laser design, which combines the advantages of active and passive Q-switching, resulting in low time jitter as well as simple drive electronics with low power consumption. The plane-plane diode pumped laser consisted of a 0.5 mm long 3% Nd3+:YVO4 crystal acting as the gain medium, with the first mirror directly coated on the input face. The laser chip was followed by the active modulator, a 2 mm long z-cut LiNbO3 crystal, which in turn was followed by the saturable absorber, a 0.6 mm thick Cr4+:YAG crystal, and the output mirror. All elements were optically bonded together and the total cavity length including mirrors was 3.5 mm. The monolithic laser has a low jitter, here limited by our driving electronics to 85 ps, at a switching voltage of 300 V, compared to the V(pi ) of 5.2 kV. The pulse length is only 3 ns when the laser operates in combined Q-switched mode and 12 ns when passively Q-switched. In addition, multiple pulses caused by the active modulator is suppressed by the saturable absorber.