A binary subwavelength four-zone transmission grating micropolarizer for conversion of a linearly polarized incident laser beam into a azimuthally polarized beam with a phase shift of π at diametrically opposite points of the beam was synthesized and characterized. The proposed micropolarizer consists of four sectors with angles -60°, 60°, -60° and 60° with the y-axis. The micropolarizer has a period 230 nm, width of step 138 nm, and width of groove 92 nm. The micropolarizer was designed for wavelength 633 nm and was manufactured in silicon (refractive index n = 3.87 – 0.016i) spattered on a glass substrate. The size of micropolarizer was equal to 100×100 μm, and the microrelief height was equal to 130 nm. The performance of designed micropolarizer was simulated using FDTD-method. A linearly polarized plane wave of wavelength 633 nm was assumed to illuminate the polarizer at the normal incidence. The mesh of the FDTD method had a λ/30 step. The field distribution at a significant distance from the polarizer was calculated using the Rayleigh-Sommerfeld integral, with the FDTD-aided complex amplitude calculated 100-nm away from the surface taken as an initial field guess. It was shown that the obtained beam focused by Fresnel zone plate with focal length 532 nm produces focal spot with diameters FWHM_x = 0.42λ and FWHM_y = 0.81λ. Focal spot formed only by the transverse component of electric field has diameters FWHM_x = 0.42λ and FWHM_y = 0.59λ.

Date Published: 14 April 2017
PDF: 6 pages
Proc. SPIE 10337, Saratov Fall Meeting 2016: Laser Physics and Photonics XVII; and Computational Biophysics and Analysis of Biomedical Data III, 103370T (14 April 2017); doi: 10.1117/12.2267950

Published in SPIE Proceedings Vol. 10337:
Saratov Fall Meeting 2016: Laser Physics and Photonics XVII; and Computational Biophysics and Analysis of Biomedical Data III
Vladimir L. Derbov; Vladimir L. Derbov; Dmitry Engelevich Postnov; Dmitry Engelevich Postnov, Editor(s)