Voltage-controlled tuning of an organic semiconductor distributed feedback laser using liquid crystals

Voltage-controlled continuous tuning of the laser wavelength of an organic distributed feedback laser is demonstrated by incorporation of liquid crystals (LCs) in the top cladding layer. Orientation of the LCs and hence the modal refractive index are controlled by applying a lateral electrical field. Laser emission shifts by 4 nm at an applied voltage of 675 V. The device showed lasing thresholds of about 286 nJ per pulse. The tuning behaviour is analyzed by implementation of a voltage-dependent spatial LC director orientation profile in a slab waveguide model and solving the Bragg condition to obtain the voltage-dependent lasing wavelength. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3610473]