888 nm pumping of Nd:YVO 4 for high-power high-efficiency TEM 00 lasers

Abstract

Nd:YVO₄ is a widely used gain medium in commercial lasers providing up to several tens of watts in a diffraction limited beam. Its high gain favors high repetition rates and short pulses in nanosecond Q-switched and picosecond mode-locked regimes. However, output power is limited by strong thermo-optical effects leading to an aberrated thermal lens and ultimately the crystal's fracture. In this contribution, we present the optimized pumping of vanadate at 888 nm, benefiting from polarization-independent absorption, reduced quantum defect and very low absorption coefficients compared to the common pump wavelengths of 808 and 880 nm. After a presentation of the principle and the key characteristics of a high-power fiber-coupled end-pumped multimode oscillator, a series of systems based on this pumping technique are presented. A compact 60W high-efficiency TEM₀₀ CW oscillator first proves the potential for high-power high-beam-quality systems. A CW intracavity-doubled system provided 62 W of power at 532 nm. A cavity-dumped Q-switched oscillator providing up to 47 W of average power with 6 ns long pulses at all repetition rates was investigated. Passive mode-locking of an oscillator providing 56 W of output power was achieved with a saturable absorber mirror. Finally, a high-power oscillator was amplified with high efficiency in a power amplifier based on the same pump/crystal configuration. The wide range of systems demonstrated illustrates the simplicity and flexibility of 888 nm pumping for extending the benefits of vanadate in the higher power range.