High-power non-astigmatic TEM₀₀ and vortex mode generation in a compact bounce laser design

Abstract

A novel design of a diode-side-pumped bounce amplifier laser is described that can produce a high-power TEM₀₀ mode and Laguerre–Gaussian (LG) vortex mode operation with high circularity and low astigmatism. The design utilises control of pump size and bounce angle such that the laser mode experiences substantially circular symmetric gain and spherical thermal lensing, in a highly compact fundamental mode resonator. In a simple plane–plane Nd:YVO₄ laser resonator with no other optical components and total length of just 13.4 cm, highly circularised TEM₀₀ operation is produced at wavelength 1064 nm, with 14.2 W of power and high beam quality M ²<1.05. Stable Q-switched TEM₀₀ operation is demonstrated up to 900 kHz and second harmonic power of 7.2 W at 532 nm is generated with conversion efficiency up to 64%. Minor modification of the design to exploit the spherical aberration of the thermal lens is shown to allow for generation of a doughnut-shaped LG vortex mode with average power 16.6 W, maintaining extremely low astigmatism. Q-switched operation of the vortex mode is accomplished up to 400 kHz. A detailed numerical thermal analysis of the amplifier design is performed and gives quantitative agreement with experimental results.