Single-photon and correlated two-photon sources are important elements for optical information systems. Nonlinear downconversion light sources are robust and stable emitters of single photons and entangled photon pairs. However, the rate of downconverted light emission, dictated by the properties of low-symmetry nonlinear crystals, is typically very small, leading to significant constraints in device design and integration. In this Letter, we study principles of spontaneous emission control (i.e., the Purcell effect) generalized to describe the enhancement of nonlinear generation of quantum light through spontaneous parametric downconversion. We develop a theoretical framework based on eigenmode analysis to study quantum nonlinear emission in a general anisotropic, dispersive, and lossy media. Our theory provides an unprecedented insight into the emission process. We find that spontaneous parametric downconversion in a media with hyperbolic dispersion is broadband and phase-mismatch-free. We further predict a significant enhancement of the downconverted emission rate in experimentally realistic nanostructures. Our theoretical formalism and approach to Purcell enhancement of nonlinear optical processes provides a framework for description of quantum nonlinear optical phenomena in complex nanophotonic structures.

中文翻译：

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超材料中的量子非线性发光：宽带Purcell增强参数下变频

单光子和相关的双光子源是光学信息系统的重要元素。非线性下转换光源是单个光子和纠缠的光子对的鲁棒且稳定的发射器。然而，由低对称性非线性晶体的特性所决定的下转换的发光速率通常非常小，从而导致器件设计和集成方面的重大限制。在这封信中，我们研究了自发发射控制的原理（即，赛尔效应），概括地描述了通过自发参数下转换来增强量子光的非线性生成。我们开发了一种基于本征模分析的理论框架，以研究一般各向异性，色散和有损介质中的量子非线性发射。我们的理论为排放过程提供了前所未有的见识。我们发现，在具有双曲分散的介质中，自发的参数下变频是宽带的，并且没有相位失配。我们进一步预测了在实验上现实的纳米结构中下转换发射率的显着提高。我们的理论形式主义和Purcell增强非线性光学过程的方法为描述复杂纳米光子结构中的量子非线性光学现象提供了框架。