Polarization-independent bandwidth-variable tunable optical filter based on cholesteric liquid crystals

Right- and left-handed cholesteric liquid crystals (CLCs) with the same reflection band at the same temperature have been successfully fabricated by doping oversaturated chiral dopant S811 (left-handed) or R811 (right-handed) in the liquid crystal host BL006. The reflection band of both the right- and left-handed CLCs is blue-shifted with an increase in temperature. On the basis of this property, a polarization-independent tunable optical filter with variable bandwidth was demonstrated by combining left- and right-handed CLCs as a unit and configuring two CLC units in the reflection mode, in which the incident light is first reflected by one pair of CLCs and then reflected by the other one. The central wavelength can be tuned from 573 to 500 nm and the bandwidth can be varied from 10 to 70 nm. (C) 2014 The Japan Society of Applied Physics