Exploiting soft organic optical resonant structure towards large range electro-optic tunable devices

Abstract

Very fine molecular arrangement of cholesteric liquid crystal (CLC), can be compressed by applying an external electric field in the liquid crystal cell geometry. This enables very fine tuning of the wavelength of the reflected light. The compression of the periodic dielectric molecular arrangement continues till the chiral energy density meets its repulsive-type excluded volume interaction and hence the corresponding resonant wavelength jumps back to the original spectral position. Experimentally, the tuning range is observed to be highly affected by the concentration of the chiral dopant in the mixture. Analytically, it is shown that, use of chiral molecules with higher helical twisting power (HTP) can reduce the concentration of the chiral dopant for a desired pitch length in visible range and hence, the spectral tuning can be exploited over the entire visible range.