Arbitrary Polarization Conversion by the Photonic Band Gap of the One-Dimensional Photonic Crystal

We demonstrate that an all-dielectric one-dimensional photonic crystal (1DPC) serves as an effective tool for arbitrary polarization conversion. Within the photonic band gaps (PBGs) of the 1DPC, perfect total reflection can be achieved. Under oblique incidence, the trends of reflection phase changes for p- and s-polarization within the PBGs are different. As the incident angle increases, the range of phase difference between p- and s-components gradually expands to (0, 2π). When light is incident with a specific polarization state, the phase difference between the p- and s-components leads to the polarization conversion of the reflected light within the PBGs. By changing the polarization direction of the incident light, arbitrary polarization state conversion covering the full Poincaré sphere can be achieved. The efficiency of this conversion can reach 100% due to the perfect reflection within the PBGs and the non-absorptive nature of the all-dielectric 1DPC.