Doped With Neodymium Vanadate Crystal 0.91¦Ìm Continuous Wave Laser Characteristics

As laser materials Nd-doped vanadate crystals, having a series of advantageous properties, have been the most important solid-state laser media along with Nd:YAG, and have found wide applications in low-to-medium power all-solid-state lasers operating at～1μm. In recent years, more and more attention has been paid to the research into the quasi-three-level laser oscillation at 0.91μm of these crystals. In this work, we have carried out a systematic, experimental and theoretical, study on the 0.91 p.m continuous-wave (cw) laser properties of Nd-doped ordered and mixed vanadates under diode laser pumping, with the primary results summarized as follows:A comprehensive summarization with analyses and comparisons has been made of the structural characters of the three Nd-doped vanadates, Nd:YVO4, Nd:GdVO4, and Nd:LuVO4, and of their thermal, optical, and spectroscopic properties that are closely related to the laser performance.The stability and mode parameters of hemispherical cavities, which are applicable to quasi-three-level lasers of Nd-doped vanadates, have been calculated on the basis of the ABCD matrix theory, providing the variations of the stability parameters and the fundamental mode radius with the thermal focal length as well as the cavity length.Room-temperature cw laser oscillation at 0.91μm has been achieved with uncoated crystals of Nd:LuVO4 and Nd:GdVO4. Slope efficiencies of 30.2% and 37.2% have been reached in the laser oscillation produced with a-cut and c-cut Nd:LuVO4 crystals, representing the highest sloped efficiency obtained up to now with this crystal.For the first time a systematic study has been conducted on the 0.91μm cw laser properties of the Nd-doped mixed vanadates of Nd:YxGd1-xVO4 with different compositions. The results show that the mixed crystal of x=0.53 exhibits the best laser performance; a cw output of 390 mW was produced at an absorbed pump power of 2.85 W, giving an optical-to-optical efficiency of 14%, whereas the slope efficiency being 25%.A theoretical model for quasi-three-level lasers with Top-hat pump beam profile has been proposed on the basis of rate-equation theory. With the help of this model, theoretical calculations have been carried out of the relationship between the output power and the pump power in the cw laser oscillation generated with different crystals of Nd:GdVO4, Nd:LuVO4, and Nd:YxGd1-xVO4, with theoretical results being in close agreement with the experimental measurement.