Polarization modulation based on rotation of a garnet with grooved films

Abstract

Garnets with grooved films are used to modulate the polarization property of a laser beam. The polarization properties of a laser beam that interacts with a garnet and grooved films are studied by Stokes polarimeters. The period of the grooved films is 400 μm and the width of the grooved films is 200 μm, which is far more than the wavelength of the laser beam. The experimental results demonstrate that the rotation of a garnet with grooved films can modulate the degree of polarization of the laser beam from 0.16 to 0.945, the arbitrary change of degree of circular polarization is larger than that the degree of linear polarization due to scattering effects.

Optical beam shift induced by direct current

“…S 1 is the intensity difference between horizontally polarized laser beam and vertically polarized laser beam, S 2 is the intensity difference between +45°polarized laser beam and −45°polarized laser beam, and S 3 is the intensity difference between right‐circularly polarized laser beam and left‐circularly polarized laser beam. The Stokes parameters S 1 of totally polarized laser beam, P‐polarized laser beam, and S‐polarized laser beam are basically unchanged and the value are −0.8, 1.0, and −1.0, respectively, when the external DC voltage value change from 0 to 2.5 V. The Stokes parameters S 2 of totally polarized laser beam, P‐polarized laser beam, and S‐polarized laser beam are basically unchanged and the value are −0.6, 0.15, and 0.1, respectively, when the external DC voltage value change from 0 to 2.5 V. The degree of optical linearly polarization (DOLP) is determined by S 1 and S 2 , and the S 1 and S 2 do not change when the external DC voltage value change, so the DOLP basically do not change. The absolute value of Stokes parameters S 3 of the totally polarized laser beam, P‐polarized laser beam, S‐polarized laser beam are basically unchanged, when the external DC voltage changes from 0 to 1.0 V. The absolute value of Stokes parameters S 3 of the totally polarized laser beam increases from 0.025 to 0.15, the absolute value of Stokes parameter S 3 of the P‐polarized laser beam increases from 0 to 0.15, and the absolute value of Stokes parameter S 3 of the S‐polarized laser beam increases from 0.25 to 0.3, when the external DC voltage increase from 1.0 to 2.5 V. The degree of circularly polarization (DOCP) of a laser beam is determined by S 3 , so the DOCP increases when the external DC voltage increases from 1.0 to 2.5 V. The DOP of the totally polarized laser beam, the P‐polarized laser beam, and the S‐polarized laser beam show different trends when the external DC voltage changes from 0 to 2.5 V. The DOP of the totally polarized laser beam begins to decrease from 80 to 75%, when the external voltage is higher than 1.0 V. The DOP of the P‐polarized laser beam increases from 82.5 to 85%, when the external voltage is higher than 2.0 V. The DOP of the S‐polarized laser beam increases from 96.5 to 100%, when the external DC voltage is higher than 1.75 V. So that, the DOCP, DOP of the totally polarized laser beam, the P‐polarized laser beam, and the S‐polarized laser beam can be changed when the external pressure changes, at different critical pressure value.…”