A Strip Sub-wavelength Radial Polarization Grating

A strip sub-wavelength radial polarization grating is designed in this paper. It is fabricated by beam direct write lithography, which can convert a rotation of polarization plane into the horizontal displacement of facula directly, so a linear measurement of rotation angle is achieved by locating the facula displacement. The grating consists of 12 000 units are arranged horizontally, the direction of the central unit is 0 degrees, and the right or the left ones are rotated in turn by 30 '' in counterclockwise or clockwise directions respectively and finally achieve a measurement range of +/- 50 degrees optical rotation angle. The theoretical model of the grating is established based on the Jones Matrix, and the relationship among the polarization characteristics and the grating ridge height, the period, the duty ratio, the incident light wavelength, the incident angle, and the temperature is analyzed by using the rigorous coupled-wave theory. The experimental and simulation results show that the grating TM wave transmittance is greater than 80%, and the extinction ratio is better than 26 dB. It achieves the optical power independent measurement of the optical rotation angle, which can be employed to build a new type of polarimeter with no mechanical rotating device or optical transducers with no rotary translation converter.