Wavelength tunable semiconductor laser with a liquid crystal pixel mirror

Abstract

Tunable semiconductor lasers are compact, versatile sources used extensively in dense-wavelength-division-multiplexing (DWDM) optical communication systems, precision metrology, environmental monitoring, and laser spectroscopy. We have developed a twisted nematic liquid crystal device, the liquid crystal pixel mirror (LCPM), successfully as electronically tunable spectral filters for wavelength selection in external cavity semiconductor lasers. In this talk, we report recent advances in this class of electronically tunable single- and multiple-wavelength semiconductor lasers at 650 and 830 nm. Preliminary results of operating the laser at 1.5 microns will also be shown. The laser output can be locked to the ITU grid at 100 GHz intervals. Output power of the laser is as high as several hundred milliwatts, with a tuning range of several tens of nanometers. The laser can be operated either in the continuous-wave (CW) or mode-locked configuration. The linewidth of the laser in the free-running CW mode is about 30 MHz. Fine-tuning of the cw output wavelength can be achieved by changing the driving voltage to the desired pixels of the LCPM. In the mode-locked configuration, the laser design allows intra-cavity dispersion compensation and pulse compression.