Single-mode Laser Tuning from Cholesteric Elastomers Using a "notch" Band-gap Configuration

The interest in the application of cholesteric liquid crystals for tunable lasers has risen in the past few years. Here, we want to obtain a mechanically tunable laser device using cholesteric liquid crystal (CLC) elastomers as resonant cavity mirrors in a three-layer configuration, which includes in between an isotropic layer incorporating a laser dye as active medium. The transmission band-gap of the two CLC elastomers was shifted one with respect to the other in order to create a defect ("notch") in the middle of the band-gap which allowed a single-mode lasing from the system. The wavelength of the laser could be changed by mechanical tuning of the rubbery device.