Integrated nanoplasmonic quantum interfaces for room-temperature single-photon sources

Abstract

We describe a general analytical framework of a nanoplasmonic cavity-emitter system interacting with a dielectric photonic waveguide. Taking into account emitter quenching and dephasing, our model directly reveals the single photon extraction efficiency, η, as well as the indistinguishability, I, of photons coupled into the waveguide mode. Rather than minimizing the cavity modal volume, our analysis predicts an optimum modal volume to maximize η that balances waveguide coupling and spontaneous emission rate enhancement. Surprisingly, our model predicts that near-unity indistinguishability is possible, but this requires a much smaller modal volume, implying a fundamental performance trade-off between high η and I at room temperature. Finally, we show that maximizing ηI requires that the system has to be driven in the weak coupling regime because quenching effects and decreased waveguide coupling drastically reduce η in the strong coupling regime. INTRODUCTIONAtomic and photonic quantum systems are central in many areas of quantum information processing, including quantum computing, communication, and precision sensing. [1][2][3] A central remaining challenge is to improve the naturally weak interaction between single photons and single emitters. [4] To this end, a plethora of approaches using dielectric (Ref. [5][6][7][8][9][10][11][12]) as well as plasmonic (Ref. [4,[13][14][15][16][17][18]20]) cavities and waveguides has been suggested. While several theoretical studies analyzed the interaction between quantum emitters and dielectric (Ref. [4,(21)(22)(23)(24)) or plasmonic (Ref. [13][14][15]) waveguides, it has been a remaining issue to develop a comprehensive physical model of a nanoplasmonic cavity interacting with a single quantum emitter and evanescently coupled to a dielectric waveguide. [25,26] In particular, there is a need for a comprehensive theoretical model to analyze the single photon extraction efficiency and indistinguishability of such integrated nanoplasmonic systems.In this paper we present for the first time a general theory framework of an integrated nanoplasmonic quantum interface which incorporates the impact of quenching and dephasing on the single photon extraction efficiency η and indistinguishability I. Our analysis yields optimal operating conditions to maximize η and I and gives clear physical intuition in the fundamental performance trade-offs. We reveal that η is maximized for an optimum cavity modal volume V opt η which is inversely proportional to the cavity Q−factor. On the other hand, I can only be maximized for much smaller V c V opt η at room temperature, imposing a fundamental limit on the ηI product. Finally, it is shown that the maximum ηI product is obtained for weak coupling because quenching effects and reduced waveguide coupling induce a huge decrease of η in the strong coupling regime. MODELThe quantum photonic platform under investigation is shown in Fig. 1. It consists of a dielectric nanophotonic waveguide that evanescently interacts with a cavityemitter system. Th...

Quantum photonics model for nonclassical light generation using integrated nanoplasmonic cavity-emitter systems

“…For plasmonic cavities, γ e contains an additional contribution due to nonradiative quenching by higher-order plasmon modes, as shown in Ref. [26], i.e., γ e = γ d…”

“…We start from a quantum photonic platform which is closely related to the one studied in Ref. [26] (see Fig. 1).…”

“…, with ω p the plasma frequency of the metal, χ κ a factor containing the overlap between the electric fields of the waveguide and the cavity, eff the relative effective dielectric permittivity of the waveguide mode, wg the relative permittivity of the waveguide core, and V c = πR 3 d the cavity modal volume [26]. As opposed to Ref.…”

“…As opposed to Ref. [26], where the decay of an initially excited emitter into the waveguide mode without any external driving was studied, we consider a system which is pumped by a continuous coherent probe field and study how the photon statistics of the classical probe field is affected by the interference with the light emitted from the cavity-emitter system. Moreover, we discuss the differences between the transmitted and reflected guided light (which in the case of Ref.…”

“…Moreover, we discuss the differences between the transmitted and reflected guided light (which in the case of Ref. [26] were identical) and derive analytical formulas for the first-and second-order correlation functions in transmission and reflection. The Hamiltonian of this quantum photonic platform is given by…”