Diode-pumped Nd:YVO₄ system for hundreds nanosecond high-power high beam quality laser generation

In this study, we successfully developed a high beam quality Q-switched pulsed laser operating at a wavelength of 1064 nm, featuring a repetition frequency of 25 kHz and an power output of 150.2 W. The system comprises a seed laser oscillator coupled with a four-stage traveling-wave amplifier, utilizing Nd:YVO₄ crystals as the medium for both oscillation and amplification stages. To mitigate the thermal effects on the crystal, we meticulously selected an appropriate laser diode (LD) wavelength, optimized the concentration and length of the crystals, and applied indium welding techniques. Additionally, we implemented thermal spherical aberration compensation to further enhance the beam quality and overall output power. We conducted an extensive analysis on the beam quality and amplification efficiency across each stage of the system. Ultimately, we achieved a frequency doubling power of 49 W using a type-I non-critical phase matching LiB₃O₅ crystal, resulting in a conversion efficiency of 32.6%. Our findings illustrate the viability of employing Nd:YVO₄ crystals in multi-stage amplification setups to produce high-power lasers with pulse durations on the order of hundreds of nanoseconds.