Theoretical determination of biaxial anisotropy suitable for reducing incident angle dependence of a high-efficiency polarization grating

A theoretical framework for determining biaxial anisotropy suitable for reducing the incident angle dependence of a polarization grating is proposed. The principal refractive indices are uniquely given by quantifying the biaxial anisotropy through the N z coefficient. The numerical analysis based on the finite-difference time-domain method reveals that the incident angle dependences of the diffraction efficiency and the polarization ellipticity of the diffracted light are significantly reduced when N z = 0.5 . This result is expected to contribute to the design of polarization diffractive optical elements and the development of anisotropic materials and structures.