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Journal of Physics B Atomic Molecular and Optical Physics

Causal nonlinear quantum optics

Stefan Scheel, D.‐G. Welsch

Published Jul 24, 2006• 13 citations
Publisher

Abstract

We present a quantization scheme for the electromagnetic field in locally responding nonlinear dielectric materials with dispersion and absorption. Based on the Green tensor expansion of the macroscopic electromagnetic field, we derive an expression for the nonlinear polarization that contains, besides the reactive part which is responsible for the nonlinear interaction, a noise contribution that has hitherto been disregarded. For the process of third-harmonic generation, we find that the magnitude of the nonlinear noise polarization is proportional to the intensity of the pump fields.

DOI
10.1088/0953-4075/39/15/s17

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We present a quantization scheme for the electromagnetic field in locally responding nonlinear dielectric materials with dispersion and absorption. Based on the Green tensor expansion of the macroscopic electromagnetic field, we derive an expression for the nonlinear polarization that contains, besides the reactive part which is responsible for the nonlinear interaction, a noise contribution that has hitherto been disregarded. For the process of third-harmonic generation, we find that the magnitude of the nonlinear noise polarization is proportional to the intensity of the pump fields.
We derive an effective Hamiltonian for the nonlinear process of parametric downconversion in the presence of absorption. Based upon the Green-function method for quantizing the electromagnetic field, we first set up Heisenberg's equations of motion for a single atom driven by an external electric field and in the presence of an absorbing dielectric material. The equations of motion are then solved to second order in perturbation theory which, in rotating-wave approximation, yields the standard effective interaction Hamiltonian known from free-space nonlinear optics. In a second step, we derive the local-field-corrected Hamiltonian for an atom embedded in a dielectric host medium, that is, a nonlinear crystal. Here we show that the resulting effective Hamiltonian is found to be trilinear in the electric and noise-polarization fields and is thus capable of describing nonlinear noise processes. Furthermore, it reduces to the phenomenological nonlinear Hamiltonian for the cases where absorption, and hence the noise-polarization field, vanishes.
We present a consistent quantum theory of the electromagnetic field in nonlinearly responding causal media, with special emphasis on Chi(2) media. Starting from QED in linearly responding causal media, we develop a method to construct the cubic Hamiltonian expressed in terms of the complex nonlinear susceptibility in a quantum mechanically consistent way. In particular, we show that the method yields the nonlinear noise polarization, which together with the linear one is responsible for intrinsic quantum decoherence.
We construct a quantum theory of light in nonlinear dielectric media with dispersion and absorption. We employ a mesoscopic model for the light-matter interaction that include a fourth-order nonlinearity in the material response. Quantization is performed by constructing an effective action in a path-integral formalism by integrating out matter and bath degrees of freedom. We show how a nonlinear response function associated with Kerr nonlinearity is obtained through the model and, after full field quantization, we derive the Feynman rules from this theory.
We construct a quantum theory of light in nonlinearly responding materials with dispersion and absorption and, in particular, show the emergence of non-Gaussian noise associated with nonlinear absorption processes. Our theory is based on a path-integral formulation of the microscopic Huttner-Barnett model including cubic matter self-interaction required for χ(2)χ^{(2)}χ(2) nonlinear processes. We show that the noise polarization emerges naturally from a decoupling of the stochastic weights of the bath response which, in case of cubic self-interactions, leads to a decoupling via Airy functions. As the theory is, by construction, consistent with the nonlinear fluctuation-dissipation theorem, it constitutes a viable quantum theory of light in nonlinear media.
We present a theoretical framework for handling quantum nonlinear processes in epsilon-near-zero (ENZ_ nano spheres, based on macroscopic quantum electrodynamics and the resonant states (RSs) expansion of the Green's tensor in nano cavities. Using third-harmonic generation (THG) as a case study, we derive analytical expressions for the generation efficiency, and the quantum fluctuations of the generated nonlinear field, as a function of different quantum states of the impinging pump field. Finally, we discuss how to generalise this theoretical framework to arbitrarily quantum nonlinear processes in photonic nanostructures.
An effective Hamiltonian for the second-order nonlinear process of parametric downconversion in the presence of absorption is derived. The electromagnetic field is quantized using the Green function method. Heisenberg's equations of motion for the interaction of a single atom with a driving electric field are then solved to second order in perturbation theory in the rotating-wave approximation. The real-cavity model is used to embed the interacting atom in a bulk medium and correct for local field effects of the material. The resulting Hamiltonian is found to be trilinear in the electric and noise polarization fields and reduces to the phenomenological nonlinear Hamiltonian for the cases where absorption vanishes.