Novel Polarization Devices: Polarization Converters, Perfect Wave plate
Waveplates are planar devices used in optics and optoelectronics to change the polarization state of light. Made of anisotropic dielectric materials such as crystals and thin films,waveplates are not known to exhibit achromatic performance over the visible regime. Inspired by the microvillar structure of R8 cells functioning as polarization converters in the eyes of stomatopod crustaceans, we conceived, designed, fabricated and tested periodically multilayered structures comprising two different types of arrays of nanorods. Morphologically analogous to the ocular cells, here we show that the periodically multilayered structures can function as achromatic waveplates over the visible regime.
This work presents a simple method to enhance polarization conversion reflection from an anisotropic thin film. The total reflection effect at the interface of an anisotropic thin film causes strong ee-ray and oo-ray couplings, leading to enhanced polarization conversion. Arranging high-refraction thin filmor low-refraction thin film in the prism/anisotropic thin film/air system yields narrowband or broadband polarization conversion reflection.
The polarization state of light is modulated by an anisotropic thin film. An anisotropic MgF2MgF2 film is deposited onto a plate that is put in contact with a BK7 prism to form a BK7 prism/film/air configuration. It is shown that the polarization state of reflected light can be easily modulated from a linear state to a circular state by rotating the thin-film plate.
This study presents a simple method for determining the optical constants of an anisotropic thin film. The sensitivity of enhanced polarization conversion reflectance to optical constants is also calculated and analyzed. Based on the sensitivity calculation, the principal indices and columnar tilt angle can be derived from the polarization conversion reflectance angular spectrum.
This work demonstrates the feasibility of applying a symmetrical film stack on a silver mirror, resulting in broadband phase retardation. While functioning as a reflective-type achromatic waveplate, the symmetrical film stack comprises at least one anisotropic thin film. Additionally, selecting the birefringence and thickness of the thin film allows for the design of uniform phase retardation in both the passband and stopband. A symmetrical film stack that is composed of an anisotropic Ta2O5 thin film and isotropic Ta2O5 thin film is investigated for its achromatic performance in phase retardation.
