Thermally Tunable Random Lasing With Switchable Modes from Disordered Cholesteric Phase of Hydroxypropyl Cellulose

ABSTRACT Tunable compact lasers hold great promise as integrated light sources for sensing, display and lab‐on‐a‐chip applications, yet most existing devices rely on complex manufacturing process or synthetic materials that conflict with environmental sustainability requirements. Here, we construct a green cholesteric liquid crystal host using plant‐derived hydroxypropyl cellulose doped with an organic laser dye. The high viscous material has disordered helical structure with thermo‐responsive property, enabling the switching between random laser and band‐edge‐enhanced random laser by regulating the photonic bandgap position relative to the gain band via temperature control. The coupling between the high‐density band‐edge state with the multiple scattering network results in tunable emission wavelength, lower lasing threshold, extended feedback path, multimode coexistence and circular polarization property. This work helps to elucidate the light‐matter interaction in complex biobased photonic structures and showcases the possibility for sustainable optical devices.