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

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 (n(e)) to the ordinary refractive index (n(o)), distribution factor chi(0) and a parameter related to the initial launch angle beta 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 refocusing effect of nonparaxial RPAiG beams is more obvious with the increasing of the parameter related to the initial launch angle beta and the ratio of n(e) to n(o). 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 chi(0) is smaller, the RPAiG beams tend to the radially polarized Gaussian (RPG) beams when chi(0) is larger. Meanwhile, the position of side lobes and the evolution speed of the radiation force can be modulated by the ratio of n(e) to n(o) and the parameter beta 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.