Multi-watt passively Q-switched self-Raman laser based on a c-cut Nd:YVO4 composite crystal

Abstract

An in-band pumped passively Q-switched (PQS) self-Raman laser with a c-cut Nd:YVO4 composite crystal is demonstrated for the first time to our knowledge. A Cr4+:YAG composite crystal was utilized to improve the stability and misalignment sensitivity of the resonator. The PQS self-Raman output performance was systematically investigated with different initial transmissions (T0) of the Cr4+:YAG and different transmissions (TS) of the Raman output coupler. In addition, the focus position of the incident pump beam and cavity length have been optimized during the experiment. With Cr4+:YAG of T0=90% and output coupler of TS=10%, the maximum average output power at 1178 nm was up to 2.53 W under the absorbed pump power of 20.6 W, corresponding to an optical-to-optical conversion efficiency of 12.3%. The pulse repetition frequency and pulse width were measured to be 39.1 kHz and 20.4 ns, respectively, and the corresponding pulse energy and peak power were calculated to be 64.7 μJ and 3.2 kW. At the full output power, the fluctuation of Raman output power was less than ±0.5% within one hour. To the best of our knowledge, we have improved the PQS self-Raman laser about 3.2 times.