Tunable Liquid Crystal Laser Using Distributed Feedback Cavity Fabricated by Nanoimprint Lithography

Electrical tuning of laser wavelength is demonstrated using a liquid-crystal/polymer grating fabricated by nanoimprint lithography. Laser emission occurs at a wavelength near 700 nm, which corresponds to the first order of a 200 nm period grating. With increasing applied voltage, the lasing spectrum begins to shift to shorter wavelengths at 10 V, and then a 10 nm shift is achieved with an applied voltage of 30 V. This is due to the refractive index change of the liquid crystal in the trench of the polymer grating by field-induced molecular reorientation.