Abstract

There is great interest in developing compact coherent light sources at wavelengths less than those of available AlGaAs/GaAs lasers, primarily for optical data storage applications. Several approaches have been pursued, one of the most promising of which is frequency doubling in nonlinear optical waveguides.^[1] An attractive method for achieving efficient SHG in a waveguide is quasi-phasematching, and this has been demonstrated both in lithium niobate^[2],[3] and poled polymers.^[4] Useful features of quasi-phasematching include the ability to use the largest nonlinear coefficient of the material, optimize optical field overlaps, and operate at any wavelength where the materials are transparent. A critical parameter is the effective length, L_eff, over which quasi-phasematching can be achieved, since the efficiency of SHG goes as L_eff². L_eff depends on the size of random thickness and index variations in the waveguide layers, and on the coherence length dependence on thickness. We report here quasi-phasematching over a distance L_eff ≈ 0.4 cm by careful choice of materials and fabrication processes.

© 1990 Optical Society of America