Wideband circular polarization reflector fabricated by glancing angle deposition

Abstract

We demonstrate a wideband circular polarization reflector fabricated as cascades of helical films with different pitch thickness by using glancing angle deposition (GLAD) technique. The full-width-at-half-maximum bandwidth of this reflector is measured from the reflectance spectra and is found about 200 nm indicating the feasibility of wideband reflector. A helical TiO(2) film with three sections, each of different pitch thickness, is also studied. It shows three Bragg peaks at different wavelengths. To select appropriate material for this circular reflector, the optical properties of 5-turns TiO(2), ZrO(2), and Ta2O(5) helical films and the porosity effect on the TiO(2) helical film are investigated.

Experimental investigation of circular Bragg phenomenon for oblique incidence

“…The exhibition of the CBP is exploited for constructing circular-polarization filters [4,7,8,[14][15][16]. As such, the variations of the center wavelength λ Br 0 and the FWHM bandwidth Δλ Br 0 with the angle of incidence θ are of interest.…”

“…Because chiral sculptured thin films (STFs) [4,13] are solid-state analogs of chiral smectic LCs, they also exhibit the CBP [4,5]. Accordingly, chiral STFs are also exploitable in circular-polarization optical devices [14][15][16][17][18][19][20].…”

Optical and Structural Properties of Bilayer Circular Filter Prepared by Glancing Angle Deposition

“…Theses spectra carry the signature of the circular Bragg phenomenon with peak wavelength, 650 nm in the Bragg regime, which occurs due to unidirectionally periodic nonhomogeneity and helical morphology along the thickness direction. This phenomenon can also be explained by using grating theory [29]: a circular plane wave of the same handedness effectively encounters the Bragg grating, while that of the other handedness does not. The peak wavelengths in the Bragg regime of these films are almost the same due to fixed pitch thickness and deposition angle [30].…”

Simplified theory of axial propagation through structurally chiral media

“…Subsequently, it was shown [2] that the polarization properties of such films are derived from two key properties: glancing angle film deposition gives rise to form birefringence of a nominally isotropic dielectric; and substrate rotation promotes the growth of helical columns giving rise to a structural helicity of the dielectric tensor. In many respects the resultant artificial chiral media resemble cholesteric liquid crystals [3], and therefore they inherit some of their applications including display technology for colour filtering [4]. However, being solid, their polarization properties are hard-wired and they are therefore better described as a one-dimensional photonic crystal, a material system around which many complementary applications have been envisaged.…”