Abstract
A planar nematic liquid crystal (NLC) cell is incorporated into a Littman-type external cavity as the wave-length-tuning device for a semiconductor laser diode. By varying the driving voltage of the NLC cell and laser diode bias current simultaneously, we demonstrate single-mode oscillation and mode-hop-free tuning over 19.2 GHz at 775 nm. The result is in good agreement with the theoretical predictions. © 2004 Optical Society of America.