Tunable lasers

The development of tunable lasers is surveyed. Basic concepts in nonlinear optics are reviewed, the growth of LiNbO3, LiIO3, and GaSe crystals is described, and system design geometries are considered. A widely tunable laser involves three stages - a pump laser, an optical parametric oscillator (OPO) which behaves like a laser but which can be tuned over a range of frequencies, and a crystal mixing system providing larger shifts to different spectral regions. One device uses an angle-tuned LiNbO3 OPO pumped at 1.064 microns by a YAG laser. The tunability is shifted in the infrared by difference mixing, and v