Design of quasi-phasematched optical frequency converters

Abstract

Quasi-phasematching design to provide an approximation to a desired spectral amplitude response A(f) is provided. An initial phase response φ(f) corresponding to A(f) is generated. Preferably, dφ(f)/dfis proportional to A(f). Alternatively, φ(f) can be a polynomial in f. A function h(x) is computed such that h(x) and H(f)=A(f)exp(iφ(f)) are a Fourier transform pair. A domain pattern function d(x) is computed by binarizing h(x) (i.e., approximating h(x) with a constant-amplitude approximation). In some cases, the response provided by this d(x) is sufficiently close to A(f) that no further design work is necessary. In other cases, the design can be iteratively improved by modifying φ(f) responsive to a difference between the desired response A(f) and the response provided by domain pattern d(x). Various approaches for binarization are provided. The availability of multiple binarization approaches is helpful for making design trades (e.g., in one example, fidelity to A(f) can be decreased to increase efficiency and to increase domain size).