An Electrically Tunable Dual-Mode Laser Based on Self-Assembled Soft Photonic Liquid Crystals.

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. [ABSTRACT FROM AUTHOR]