Effect of mirror reflectivity on the symmetry of high-order HG and LG modes in off-axis pumped Nd: YVO₄ laser

Abstract The dependence of the symmetries of Hermite–Gaussian (HG) mode on system loss is theoretically analyzed through intracavity resonant mode superpositions. In the experiments, asymmetrical HG <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msub> <mml:mrow/> <mml:mrow> <mml:mi>m</mml:mi> <mml:mo>,</mml:mo> <mml:mn>0</mml:mn> </mml:mrow> </mml:msub> </mml:mrow> </mml:math> modes of m = 0–9 are obtained using an off-axis pumped Nd: YVO 4 laser with different output mirror reflectivities, and their symmetries are quantitatively analyzed. Experimental results demonstrate that as the output mirror reflectivity decreases from 95% to 81%, 60%, and 50%, the symmetries of the HG mode reach 93%, 70%, 43%, and 14%, respectively, consistent with numerical simulation results. The symmetry of the Laguerre–Gaussian (LG) beam obtained through an astigmatic mode converter is almost identical to that of HG. Furthermore, the output powers of asymmetrical LG modes with different transverse orders exceed 1 W with a pump power of 6.36 W. These high-power asymmetrical LG modes are useful in the research of asymmetrical vortex beams.