Laser initiated thermal tuning of a cholesteric liquid crystal

We report on the large wavelength range and light-initiated thermal tuning of the reflection of a liquid crystal (LC) formulation (S811/ZLI-2806) near a smectic (SmA) to cholesteric (CLC) phase transition enabled by the use of a high order parameter heat transfer dye (anthraquinone, AQ). Upon irradiation with a 647 nm Krypton ion ( Kr + ) laser line, absorption by AQ generates heat that is transferred to the surrounding LC host. In the S811/ZLI-2806 formulation examined here, the optically generated increase in temperature serves to transition the phase from SmA to CLC. As has been documented, the SmA → CLC transition is typified by a pitch contraction that blueshifts the position of the CLC reflection, in this case a shift from 2500 to 700 nm that can occur in less than 100 s. The tuning range and speed are dependent on the laser power and the amount of dye in the cell.