Nonlinear optical device for middle infrared generation

摘要

An alternative to Quasi Phase Matching (QPM), called Semi Quasi Phase Matching (SQPM) is proposed, wherein the segments of crystals with inverted axis are substituted by segments of small polycrystal grains of the same material. These segments produce negligible nonlinear interaction, while still providing the n phase change necessary. A SQPM device of length L should produce the same nonlinear output as a QPM device of length L/2. Crystals with higher nonlinear coefficients and larger transparency ranges like III-V and II-VI compounds, not normally amenable to inversion of axes, can be used. This is especially important for doubling of CO_2 laser lines.