Compact-cavity two-dimensional Hermite-Gaussian lasing enabled by birefringence-induced astigmatism

We report controllable two-dimensional (2D) Hermite-Gaussian (HG) lasing in a compact plano-concave cavity by exploiting the intrinsic birefringence of an a-cut Nd:YVO₄ crystal. The birefringence-induced astigmatism provides modal discrimination against tilted one-dimensional (1D) competitors, allowing axis-aligned HG_m,n modes to oscillate under 2D off-axis pumping. By increasing the birefringent crystal length, the output evolves from tilted 1D modes to axis-aligned 2D HG modes. We further show that cavity-length design can enhance the same modal discrimination, enabling 2D HG oscillation in a shortened-cavity configuration. These results verify a simple and compact route to controllable two-index HG lasing without pump shaping or intracavity loss elements.