Lasing effect in blue phase liquid crystal

We report on the investigation of random lasing in blue phase liquid crystals. Multiple scattering and interference effects arising from disordered platelet texture as well as index mismatch between polymer and mesogen contribute the optical feedbacks towards laser action. In pure blue phase liquid crystals, the random laser can be switched between the coherent and incoherent types by executing distinct heating/cooling cycles; and, the randomness of lasing wavelengths can be determined by the platelet size, which can be set by controlling the cooling rate. After the blue phase liquid crystals are polymer-stabilized, coherent random lasing may occur in both the blue phase with an extended temperature interval and the isotropic liquid state; also, the selected modes are constant from one pulse to another. Additionally, if the laser dye is sensitive to temperature, the excitation threshold and the emission spectrum could be altered via thermal control.