Low-voltage and wide-band tuning of lasing in a dye-doped liquid-crystal sandwich structure

This paper reports the electrical tuning of a lasing in a liquid crystal (LC) sandwich structure. A dye-doped nematic LC (NLC) layer is sandwiched between two CLC layers to act as a phase retarder with the CLC layers acting as cavity mirrors, for the selective reflection of light in the photonic band with the same sense of helix handedness as that of the CLC layers. The transmittance spectrum of the sandwich cell provides a large range of modulation due to the wavelength dependent nature of phase retardation between the optical eigenmodes in the NLC layer. Lasing occurs at wavelengths corresponding to the maximum transmittance within the reflection band of the CLC layers. The application of voltage to the NLC layer makes it possible to shift the wavelengths of maximum transmittance, thereby tuning the wavelength of lasing. In these experiments, an applied voltage of 1.25 V was sufficient to shift the lasing peak wavelength by approximately 47 nm.