Electrically Controlled Switching Of Mixed Mode Laser Within The Band-Gap Of Cholesteric Liquid Crystal

Both random laser and multimode band-edge laser have been found in cholesteric liquid crystals (CLCs). In this work, the laser emission in CLC with negative dielectric anisotropy under electric fields with different frequencies is investigated. Awide multi-wavelength lasing is achieved via the formation of multiple domains induced by low-frequency alternating current (AC) in the CLC system. The photonic bandgap with aweak reflection for aspecific band can also be observed in the multiple domains structure. Furthermore, two types of liquid crystal hosts with different birefringences are used to obtain different lasing cover ranges. The range of the multi-wavelength lasing is within the CLC bandgap and positively correlated to the bandwidth of the bandgap. In addition, ahigh-frequency AC or direct current (DC) can switch it to aband-edge laser based on the regular planar helical structure. The wide range switchable multi-wavelength laser may provide various applications, such as sensing and communication.[GRAPHICS]