Wavelength tuning and multiple wavelength generation using a reflection-type liquid crystal spatial light modulator

Abstract

A reflection-type spatial light modulator using twisted nematic (TN) liquid crystal (the liquid crystal pixel mirror or LCPM) is employed to realize a new type of digitally tunable, narrow line-width (< 0.1 nm, instrument-limited), multiwavelength semiconductor laser. The laser is based on a novel folded telescopic grating-loaded external cavity with LCPM at the focal plane of the folded telescope. With a 50-pixel LCPM, the single wavelength digitally tunable range of a visible laser diode was from 650.8 to 661.24 nm in 0.21 nm steps by biasing the individual pixels. Further, the wavelength can be switched and reset with a response time of 13.6 ms. By biasing two pixels at the same time, obtain dual-wavelength output with the wavelength tunable from 0.21 to 10.4 nm. Generation of tunable triple wavelengths with equal or arbitrary wavelength separation are also demonstrated. Preliminary results on such a laser operating at 1550 nin is also shown.