Generation of Longitudinally Polarized Optical Needle Using High-Order Laguerre-Gaussian Radially Polarized Beam

In this paper, the tight focusing light field of high-order radially polarized Laguerre-Gaussian beams in the focal plane of single lens was studied, longitudinal polarized optical needles were obtained. By adjusting orders of the incident beam amplitude, the effects of high-order and low-order radially polarized Laguerre-Gaussian beams on the light field under the same $\beta$ condition were compared. As the amplitude order increasing, the corresponding depth of focus progressively increased. The super-resolution optical needle was obtained by modulating the fifth-order radially polarized Laguerre-Gaussian beams. The length of the generated optical needle has increased from $2.44\lambda$ without addition of diffractive optical elements to $9.844\lambda$ at present, and the full width half maximum decreased from $0.44\lambda$ to $0.36\lambda$. The results indicated that introducing multi-ring binary phase filter into the focusing system can effectively increase the length of the optical needle and reduce the transverse size. The conversion efficiency was also increased to 50.43%. The resulting super-resolution longitudinally polarized optical needle has broad applications in particle manipulation, super-resolution imaging, nanolithography, and related fields.