Efficient Fluorescence Utilization and Photon Density of States-Driven Design of Liquid Crystal Lasers

Liquid-crystal random lasers (LCRLs) represent a burgeoning field in soft-matter photonics, holding promise for ushering in an era of ultrathin, versatile laser sources. Such lasers encompass a multitude of remarkable features, including wide-band tunability, large coherence area and, in some cases, multidirectional emission. In this paper, an LCRL is developed by doping a laser dye, pyrromethene 597 (PM597), into cholesteric LC, but achieving a wide-range wavelength-controllable (560-720 nm) bandgap lasing through voltage control. Bandgap lasing intriguingly occurs in media with extremely low dye gain, which is mainly contributed by the extremely high photon density of states (DOS) at the edge of the LC bandgap. In addition, the utilization rate of the fluorescence spectrum (550-750 nm) of laser dye PM597 is as high as 80%. The multivariate linear regression model is used to characterize the inherent relationship between the lasing intensity emitted by LC and the photon DOS, fluorescence quantum yield, and internal scattering under specific pumping energy. This model shows the potential to predict the critical conditions of laser emission accurately and provides the capability to design and fabricate large-scale multifunctional responsive photonic crystals using a simple fabrication procedure. This article presents an electric field-responsive liquid crystal bandgap laser (560-720 nm). Notably, even in the case of extremely low dye gain, bandgap lasing persist. Furthermore, the fluorescence spectral utilization of laser dye PM597 reaches an astonishing 80%. Subsequently, authors establish a model outlining the intrinsic relationship between laser emission intensity and photon DOS, fluorescence quantum yield, and internal scattering. image