Nonlinear optical response of superlattices: Multistability and soliton trains

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Abstract
For models of finite superlattices, we calculate the power dependence of the transmissivity, when one film in each unit cell exhibits a nonlinear response to the electromagnetic field. We assume the nonlinearity has its origin in the spins in an antiferromagnetic film, illuminated with frequency near resonance; one then has a term in the magnetic susceptibility proportional to the local field intensity. Results very similar to ours follow for the case where the nonlinearity occurs in the dielectric response. The response is dependent on whether the frequency of the radiation lies within a stop gap of the dispersion relation of the infinite structure calculated in linear theory, or within our allowed band of propagating waves. In the former case, we find soliton trains and multistability, as discussed earlier by Chen and Mills. In the latter, we have multistability and transmissivity gaps similar to those reported earlier by Delyon et al. The method used presently is adapted from that employed by Delyon and co-workers; we discuss its relation to alternate computational approaches. DOI: http://dx.doi.org/10.1103/PhysRevB.37.8072 © 1988 The American Physical Society