Quarter-wave retardation can be achieved in optical tunneling through a low-index thin film that is surrounded by a medium of higher refractive index, for any index ratio N>2.414, over a range of incidence angles that is determined by N. A novel frustrated-total-internal-reflection circular polarization beam splitter (CPBS) is proposed that uses an adjustable air gap between two Ge prisms. This tunable CPBS operates over a broad (2-12 µm) IR spectral range by controlling the air-gap thickness to match one-tenth of the wavelength of light by use of a piezoelectric transducer.
© 2005 Optical Society of America
R. M. A. Azzam and Cristina L. Spinu, "Linear-to-circular polarization transformation upon optical tunneling through an embedded low-index film," Opt. Lett. 30, 3183-3185 (2005)