Narrowing of filters and laser mirror in tilt-modulated chiral sculptured thin films

Abstract

Helicoidal multi-layered nanostructures obsess intriguing optical properties to develop various optical and photonic devices. The optical properties of such spiral materials are adjacent with helical rotation. Tilt-modulated chiral sculptured thin film (STF) can totally reflect or transmit light in the Bragg regime for varying amplitudes of oscillation angles. Particularly, twist defect chiral STFs of same handedness creating spectral hole for circularly polarized light at different oscillation amplitudes. A narrow bandstop or wide bandpass filters and Bragg reflectors are created in defect modulated chiral STF. While, increasing the number of oscillations in a structural half period of chiral STF, the filters are flattering and narrower having blue shift. For large number of oscillation, the modulated chiral STF behave as laser mirror and creating Bragg fringes in the Bragg regime. Similarly, for different angles of incidence light the spectral holes and optical filters are become narrowing and shifted to lower wavelength regime, eventually die out in the Bragg regime, with maximum reflection for large angle of incident light. Therefore, it is suggested that such chiral STF are very useful in optical devices which operating in different wavelength regime.