Fabrication of anisotropic diffractive optical element by using polarization drawing method based on galvanometer scanner

Abstract

Polarization is one of the important parameters of the light wave. Diffractive elements, which can control the polarization, have been attracted as high-performance light control device. We have implemented various studies on the formation method and the diffraction characteristics of the anisotropic diffractive element using a photoreactive material. Photocross linkable polymer liquid crystal (PCLC) is an attractive material that can induce anisotropy along the polarization direction of linearly polarized ultraviolet light (LPUV). Also, owing to its relatively large anchoring strength, PCLC have been used as an alignment film of low-molar-mass liquid crystal (LC). Galvanometer scanners (GS) can freely control the exposure position of the laser beam by adjusting the two mirrors, it is possible to form a highly functionalized optical element by drawing the arbitrary exposure lines to the photo-reactive material with temporally changing the polarization state of the laser beam. In this study, we report the polarization drawing method based on GS for the fabrication of anisotropic diffractive optical elements. First, the two types anisotropic diffractive optical elements were fabricated on the PCLC films. To investigate the diffraction properties of fabricated anisotropic diffractive optical elements, we used a polarized He-Ne laser beam as probe and observed diffracted lights. Diffracted beam was twodimensionally emitted depending on the formed anisotropic optical distribution. Then we fabricated LC cell, which works as polarization dependent anisotropic Fresnel lens. The experimental investigations show that it has functions of light condensing and polarization control. From these results, high-performance light control device can be fabricated by the polarization drawing method.