Swept-wavelength tunable laser in dye-doped cholesteric film based on direct refractive-index tuning

Abstract

A tunable cholesteric liquid crystal laser driven by refractive index modulation is demonstrated. The laser is fabricated simply by polymerizing a 1:1 mixture of photopolymerizable and non-photopolymerizable cholesteric liquid crystals. A network of nano-pores filled with liquid crystals with an average diameter of 10 nm is formed in the photopolymerized cholesteric liquid crystal film. Tuning is achieved by applying a voltage across the film, which reorients the liquid crystal in the nano-pores. Because of the local reorientation process, the speed of tuning is in the sub-ms range and is much faster than conventional cholesteric lasers which rely on pitch modulation. A maximum tuning range of 11 nm was achieved at an electric field of 280 V/um.