Abstract: This invention is directed to a new class of nonlinear optical device (NLO). For this purpose, in one aspect of this invention, a nonlinear optical device including a first nonlinear optical grating is presented. According to one version of the invention, the first nonlinear optical grating comprises a plurality of adjacent nonlinear optical units arranged in series. Each NLO unit has a single crystal segment and a polycrystalline segment. The single crystal segment is composed of a nonlinear optical crystal material and has its length adapted to provide the nonlinear optical effect. The polycrystalline segments are adapted in length to compensate the phase mismatch among the waves that occur in the single crystal segment.

Abstract: A nonlinear optical device including at least a first nonlinear optical grating is provided. The first grating comprises a plurality of adjacent nonlinear optical (NLO) units. Each NLO unit has a single crystal segment and a polycrystalline segment. The single crystal segment is formed from a single crystal of a nonlinear optical material and has a length adapted to provide a nonlinear optical effect. The polycrystalline segment has a length adapted to compensate for phase mismatch that occurs in the single crystal segment. Including a polycrystalline segment in each NLO unit allows for a type of quasi-phase-matching to be achieved in the first nonlinear optical grating. The first grating may be used to form a variety of nonlinear optical devices, including, for example, frequency doublers, frequency adders, frequency subtractors, amplifiers, parametric oscillators, and optical mixers. Further, the first grating may form the core of a waveguide.