Nonlinear Interactions of Light with Fundamental Systems

M. De Angelis

We have studied quantum effects in a system governed by the spatial nonlinear Schrodinger equation derived for a two beams interaction in a quadratic nonlinear material. For a quadratic nonlinear material it has recently been demonstrated [2, 3] that, under suitable conditions, in the interaction between the fundamental and the second harmonic field, the fundamental field propagation can be described as a solution of a nonlinear Schroedinger equation, given in terms of spatial solitons [4,5]. In this work we are interested at the quantum properties of the fundamental beam in this kind of interaction. We use a quantum field description [1] where the spatial variable of propagation z plays the role of time in the standard quantum theory, and we apply it to the case of a strong plane wave that can be described as a classical field propagating through the nonlinear medium in the z-direction. We assume TE polarizations for all the monochromatics fields involved into the interaction in a type I material.

Dmitry Strekalov, Gerd Leuchs

Valerii S. Butylkin, Yury G. Khronopulo, A. E. Kaplan +1 more

Chuan‐Cun Shu, Daoyi Dong, Ian R. Petersen +1 more

The absorption of a single photon that excites a quantum system from a low to a high energy level is an elementary process of light-matter interaction, and a route towards realizing pure single-photon absorption has both fundamental and practical implications in quantum technology. Due to nonlinear optical effects, however, the probability of pure single-photon absorption is usually very low, which is particularly pertinent in the case of strong ultrafast laser pulses with broad bandwidth. Here we demonstrate theoretically a counterintuitive coherent single-photon absorption scheme by eliminating nonlinear interactions of ultrafast laser pulses with quantum systems. That is, a completely linear response of the system with respect to the spectral energy density of the incident light at the transition frequency can be obtained for all transition probabilities between 0 and 100% in multilevel quantum systems. To that end, a multiobjective optimization algorithm is developed to find an optimal spectral phase of an ultrafast laser pulse, which is capable of eliminating all possible nonlinear optical responses while maximizing the probability of single-photon absorption between quantum states. This work not only deepens our understanding of light-matter interactions, but also offers a way to study photophysical and photochemical processes in the ``absence'' of nonlinear optical effects.

Lu Qin, Zeyun Shi, Xingdong Zhao +3 more

Abstract Rydberg atoms, characterized by their giant polarizability and strong long-range interactions, provide an ideal platform for exploring optical nonlinearities. By coupling light to ensembles of Rydberg atoms, one can map the strong and nonlocal interactions between Rydberg atoms and light fields. A particularly important scheme for realizing such nonlinearity is electromagnetically induced transparency (EIT). This article presents a review of the research progress in nonlinear optics based on Rydberg-EIT systems, particularly nonlinear light propagation in Rydberg atomic gases. We first introduce the fundamental properties of Rydberg atoms and the physical mechanism of EIT-enhanced nonlinearity, emphasizing how the Rydberg blockade effect endows the system with a giant nonlocal Kerr nonlinearity. Subsequently, we discuss some typical nonlinear optical phenomena in such a system with focusing and defocusing nonlocal nonlinearities. In the focusing regime, we discuss spatial solitons, vortex solitons, soliton cloning, soliton molecules, optical bullets, and self-induced transparency solitons. Other topics are also discussed. In the defocusing regime, we analyze pattern formation and shock wave dynamics. Finally, we provide an outlook on the future development of this field toward quantum control, hybrid-system integration, and novel functional devices.

Ralf Menzel