Abstract

The past decade has seen a renaissance in coherent sources based on nonlinear optical frequency conversion, fueled by improved pump lasers and improvements in available nonlinear materials. Microstructured nonlinear materials, especially those in which the nonlinear susceptibility is periodically reversed to quasi-phasematch (QPM) the nonlinear interaction, are playing an increasingly important part in these developments. Application of periodically poled ferro-electrics, the most important class of QPM materials, has allowed qualitative improvements in coherent sources from the ultraviolet to the mid-infrared. The increase in conversion efficiency available with these materials also enables effective application of quadratic nonlinear optics beyond simple sources of coherent radiation, in fields such as quantum optics, wavelength conversion for WDM systems,, and cascade nonlinearities. By shifting the emphasis from materials with appropriate birefringence to those with patternable nonlinear properties, the use of QPM opens opportunities to take advantage of the attractive properties of materials not traditionally used in frequency conversion applications, such as cubic III-V and II-VI semiconductors, polymers, and glasses.

© 1996 Optical Society of America