Toward practical application of cholesteric liquid crystals to tunable lasers

To realize practical application of cholesteric liquid crystals (CLCs) to photonic tunable laser devices, two efforts have been made: (1) photopolymerization and (2) use of third-harmonic generation (THG) for excitation. The proposed system is based on a spatial optical-pitch gradient in CLCs and doping of two organic dyes (Forster couple) with a concentration gradient. We obtained position-sensitive laser emissions covering the whole visible region (from 480 nm to 670 nm) in photopolymerized CLC films under excitation at 410 nm by an optical parametric oscillator. Preliminary data using more conventional pumping source (THG of a Nd:YAG laser) are also reported.