An Electrically Tunable Dual‐Mode Laser Based on Self‐Assembled Soft Photonic Liquid Crystals
Yu‐Chuan Tsao, Hui‐Yu Chen, Yang‐Fang Chen
Abstract
Abstract Soft photonic liquid crystals with electrically responsive properties are among the most promising intelligent materials for optoelectronic applications. This work demonstrates an ultra‐fast electrically tunable dual‐mode laser by introducing dye‐doped chiral liquid crystals. Due to the strong chirality of the chiral liquid crystal, two self‐assembled structures form depending on the temperatures. One is the chiral nematic phase (N*) with a 1D helical structure; the other is the blue phases (BPs) with 3D cubic structures. By tuning the strength of an electric field, the dye‐doped chiral liquid crystals are operated in two different modes: a band‐edge laser and a random laser. In the band‐edge mode, due to the electrostriction effect of the BPs, the electric‐tuning range of the laser emission is from 537 to 645 nm, and the switching times are less than 20 ms. When the electric field goes beyond a threshold value to force the occurrence of the BPs‐chiral‐nematic transition, the band‐edge laser with elliptical polarization emission is switched to a random laser with an immediate unpolarization emission (0.9 ms). Furthermore, the reversibility of the effects mentioned above points out the potential applications of self‐assembled soft photonic materials, spanning from solid‐state lighting to bio‐imaging.