Highly controllable form birefringence in subwavelength-period grating structures fabricated by imprinting onpolarization-sensitive liquid crystalline polymers

A subwavelength-period grating made in an intrinsic anisotropic medium was experimentally fabricated by means of imprinting and subsequent photoinduced molecular alignment of photocrosslinkable polymer liquid crystals (PCLC). Optical properties including the total birefringence and optic axis were theoretically and experimentally investigated by varying the crossing angle between the grating vector and the polarization azimuth of linearly polarized ultraviolet light for the photoalignment of PCLC. The total birefringence and optic axis were well-controlled by both form birefringence due to the subwavelength-period grating structure and intrinsic birefringence induced by photoalignment of PCLC. The finite-difference time-domain (FDTD) method was an effective tool for characterizing the optical properties of a subwavelength-period grating made in an intrinsic anisotropic medium.