One- and two-dimensional ring array formed by birefringence in tandem with conical refraction: experimental...

This paper was a continuation of our previous work on the formation of 2m ring beam array by using the cascade of m birefringent (BR) crystals and a conical refraction (CR) crystal. The propagation of a circularly polarized Gaussian beam through two BR crystals (m = 2) and then a CR crystal was numerically simulated to develop the theoretical framework. In this study, the experimental validation was conducted by arranging two BR YVO₄ crystals (m = 2) and a CR KGW crystal in a cascade sequence, resulting in a parallelogram array of four CR rings formed at the focal plane. Additionally, by adjusting the relative orientation of two BR crystals and rotating a half-wave plate between them, this parallelogram CR ring array could be transformed into linear or rectangular CR ring arrays, respectively. The experimental results showed good agreement with the theoretical ones.