Polarization of light significantly affects how light behaves during total internal reflection (TIR). When light undergoes TIR at the boundary between two media, its behavior depends on its polarization—whether it’s polarized parallel (p-polarized) or perpendicular (s-polarized) to the plane of incidence.
- s-Polarized light (perpendicular to the plane): This component reflects with its electric field perpendicular to the plane of incidence. Under TIR, it undergoes complete reflection, and its phase changes depending on the angle of incidence.
- p-Polarized light (parallel to the plane): This component also undergoes TIR, but the phase shift it experiences differs from that of s-polarized light. This phase difference between the two components leads to elliptical polarization if the incident light was linearly polarized.
- Phase shift and polarization change: Although the intensity of light is preserved in TIR, the phase change introduced is different for s- and p-polarized components. This causes a rotation or change in the state of polarization. If unpolarized or linearly polarized light hits the surface at TIR conditions, the reflected beam can become elliptically or circularly polarized.
- Fresnel rhombs and phase retarders: Devices like Fresnel rhombs exploit this property by using TIR to introduce controlled phase shifts, turning linearly polarized light into circularly polarized light or vice versa, without using birefringent materials.
Thus, TIR doesn’t just reflect light—it can also alter its polarization state due to the phase differences introduced between polarization components.