Nonparaxial propagation of the radially polarized Airy-Gaussian beams with different initial launch angles in uniaxial crystals

Abstract

We investigate nonparaxial propagation properties of the radially polarized Airy-Gaussian (RPAiG) beams with different initial launch angles in uniaxial crystal orthogonal to the optical axis. The influences of both the ratio of the extraordinary refractive index (ne) to the ordinary refractive index (no), distribution factor χ0 and a parameter related to the initial launch angle β on the intensity evolution, the gradient force and the scattering force of the nonparaxial RPAiG beams are analyzed and described in detail. Our results indicate that the re-focusing effect of nonparaxial RPAiG beams is more obvious with the increasing of the parameter related to the initial launch angle β and the ratio of ne to no. Furthermore, as the propagation distance increases, the intensity of the side lobes continues to flow into the main lobe until the intensity distribution of main lobes reaches the maximum, finally that of the main lobe will move into the side lobes and the intensity pattern of the main lobe will gently divide into two Airy-like patterns. One can see that the RPAiG beams tend to radially polarized Airy (RPAi) beams when χ0 is smaller, the RPAiG beams tend to the radially polarized Gaussian (RPG) beams when χ0 is larger. Meanwhile, the position of side lobes and the evolution speed of the radiation force can be modulated by the ratio of ne to no and the parameter β in the observation plane. The investigation of the nonparaxial propagation characteristics of the RPAiG beams may have potential applications in the particles trapping and optical tweezers.