Actively Q switched radially polarized Ho:YAG laser with an intra-cavity laser-written S-waveplate
Matthew J. Barber, P. C. Shardlow, Yuhao Lei, Peter G. Kazansky, W.A. Clarkson
Abstract
Nanosecond Q switched pulses and radial polarization are established stand-alone techniques for enhanced laser materials processing applications, but are generally challenging to achieve simultaneously at high average power levels. Here, we demonstrate a 20.6 W radially polarized Ho:YAG rod laser which has been actively Q switched in order to generate <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mn>515</mml:mn> <mml:mtext> </mml:mtext> <mml:mrow class="MJX-TeXAtom-ORD"> <mml:mi>μ</mml:mi> </mml:mrow> </mml:math> J, 210 ns pulses at 2097 nm. By utilizing an ultra-low-loss spatially variant birefringent wave plate (S-waveplate) inside the laser cavity, the linearly polarized fundamental mode has been converted to a radially polarized donut-shaped beam with very high conversion efficiency.