Narrow bright or dark resonances associated with electromagnetically induced transparency play a key role in enhancing photon-photon interactions. The schemes realized to date relied on the existence of long-lived atomic states with strong van der Waals interactions. Here, we show that by placing an atomically thin semiconductor with ultrafast radiative decay rate inside a microcavity, it is possible to obtain extremely narrow dark or bright resonances in transmission. While breaking of translational invariance sets a limit on the width of the dark resonance width, it is possible to obtain a narrow bright resonance that is much narrower than the cavity and bare exciton decay rates and is protected against disorder by tuning the cavity away from the excitonic transition. Resonant excitation of this bright resonance yields strong photon antibunching even in the limit where the interaction strength is arbitrarily smaller than the non-Markovian disorder broadening and the radiative linewidth of the bare exciton. Our findings suggest that atomically thin semiconductors which exhibit large exciton-cavity coupling and small nonradiative line broadening could pave the way for the realization of strongly interacting photonic systems in the solid state.
Narrow bright or dark resonances associated with electromagnetically induced transparency play a key role in enhancing photon-photon interactions. The schemes realized to date relied on the existence of long-lived atomic states with strong van der Waals interactions. Here, we show that by placing an atomically thin semiconductor with ultrafast radiative decay rate inside a microcavity, it is possible to obtain extremely narrow dark or bright resonances in transmission. While breaking of translational invariance sets a limit on the width of the dark resonance width, it is possible to obtain a narrow bright resonance that is much narrower than the cavity and bare exciton decay rates and is protected against disorder by tuning the cavity away from the excitonic transition. Resonant excitation of this bright resonance yields strong photon antibunching even in the limit where the interaction strength is arbitrarily smaller than the non-Markovian disorder broadening and the radiative linewidth of the bare exciton. Our findings suggest that atomically thin semiconductors which exhibit large exciton-cavity coupling and small nonradiative line broadening could pave the way for the realization of strongly interacting photonic systems in the solid state.
We investigate a GaAs/(Ga,Al)As Fabry-P\'erot microcavity, into which (In,Ga)As quantum wells have been inserted. The cavity is wedge shaped, i.e., the detuning between the bare-exciton resonance and the bare optical cavity mode depends on the spatial position on the sample. Linear transmission spectra reveal a well-resolved Rabi splitting of 8 meV at resonance, an inhomogeneously broadened exciton transition of 4--5-meV width, and an 0.7-meV-wide Fabry-P\'erot mode. The time-resolved transmission exhibits deep beatings and a subpicosecond exponential decay: a behavior similar to that foreseen in the strong-coupling regime and in the absence of electronic disorder. Conversely, the four-wave mixing response appears weakly influenced by the cavity and not much different from what is expected for bare excitons. A photon echo, dephasing times as long as 50 ps, and only weak Rabi oscillations are observed. The experimentally observed features can be explained by a model based on the numerical solutions of the Maxwell-Bloch equations. This model confirms the dramatic influence structural disorder in the quantum wells has on the coherent nonlinear exciton-photon dynamics.
We investigate the generation of strong antibunching photons/photon pairs in a two-atom cavity QED system leveraging interatomic van der Waals (vdW) interaction. We show that the vdW interaction shifts the energy of double excited state, enabling the suppression of two-photon excitation via destructive interference in a diamond configuration. This leads to antibunching photon emission with extremely high purity. Furthermore, by tuning the vdW interaction strength, the conditions for conventional and unconventional photon blockades can be satisfied simultaneously, which significantly enhances the generation of single photon. Conversely, at the antiblockade excitation frequency, quantum Monte Carlo simulations demonstrate the feasibility of generating antibunching photon pairs with a high purity and reasonable leaking rate by selecting appropriate driving field Rabi frequency and vdW interaction strength. These findings on enhanced photon antibunching and photon pair emission may lead to more efficient and brighter quantum light sources, which is a key mechanism for optical quantum devices.
The emergence of photonic quantum correlations is typically associated with emitters strongly coupled to a photonic mode. Here, we show that semiconductor Rydberg excitons, which are only weakly coupled to a free-space light mode can produce strongly antibunched fields, i.e., quantum light. This effect is fueled by a micron-scale excitation blockade between Rydberg excitons inducing pair-wise polariton scattering events. Photons incident on an exciton resonance are scattered into blue- and red-detuned pairs, which enjoy relative protection from absorption and thus dominate the transmitted light. We demonstrate that this effect persists in the presence of additional phonon coupling, strong nonradiative decay, and across a wide range of experimental parameters. Our results pave the way for the observation of quantum statistics from weakly coupled semiconductor excitons.
Excitonic superradiance has been predicted to induce a rapid decay rate of coherently excited excitons in thin quantum wells and microspheres. In this paper we revisit this problem and derive the enhancement factor of the radiative decay due to superradiant effects. In a GaAs quantum well, the excitonic superradiant radiative decay can be roughly 320 times faster than the decay of a free electron-hole pair. The exciton decay rate depends strongly on the lateral size of the wave function when the size is smaller than the inverse of the wave vector of the emitted light. In a GaAs quantum well this corresponds to a distance of \ensuremath{\approxeq}365 \AA{}. Therefore, it is predicted that localization and elastic phonon scattering may lead to decay rates substantially smaller than that predicted for an ideal quantum well. It is also shown that if the quantum well is placed inside a microcavity, the decay rate can be enhanced even further since the cavity modifies the available density of radiation states in a way that matches the superradiant emission. It is predicted that in a matched dielectric cavity the decay rate can be enhanced by an additional factor of 100, but that inhomogeneous broadening may in practice limit the possible enhancement.
We present an experimental proposal to achieve a strong photon blockade by employing electromagnetically induced transparency (EIT) with a single alkaline-earth-metal atom trapped in an optical cavity. In the presence of optical Stark shift, both the second-order correlation function and cavity transmission exhibit asymmetric structures between the red and blue sidebands of the cavity. For a weak control field, the photon quantum statistics for the coherent transparency window (i.e., atomic quasi-dark-state resonance) are insensitive to the Stark shift, which should also be immune to the spontaneous emission of the excited state by taking advantage of the intrinsic dark-state polariton of EIT. Interestingly, by exploiting the interplay between the Stark shift and control field, the strong photon blockade at atomic quasi-dark-state resonance has an optimal second-order correlation function g ( 2 ) ( 0 ) ∼ 10 − 4 and a high cavity transmission simultaneously. The underlying physical mechanism is ascribed to the Stark shift enhanced spectrum anharmonicity and the EIT hosted strong nonlinearity with loss-insensitive atomic quasi-dark-state resonance, which is essentially different from the conventional proposal with emerging Kerr nonlinearity in cavity-EIT. Our results reveal a new strategy to realize high-quality single photon sources, which could open up a new avenue for engineering nonclassical quantum states in cavity quantum electrodynamics.
Excitons in a semiconductor monolayer form a collective resonance that can reflect resonant light with extraordinarily high efficiency. Here, we investigate the nonlinear optical properties of such atomistically thin mirrors and show that finite-range interactions between excitons can lead to the generation of highly nonclassical light. We describe two scenarios, in which optical nonlinearities arise either from direct photon coupling to excitons in excited Rydberg states or from resonant two-photon excitation of Rydberg excitons with finite-range interactions. The latter case yields conditions of electromagnetically induced transparency and thereby provides an efficient mechanism for single-photon switching between high transmission and reflectance of the monolayer, with a tunable dynamical timescale of the emerging photon-photon interactions. Remarkably, it turns out that the resulting high degree of photon correlations remains virtually unaffected by Rydberg-state decoherence, in excess of nonradiative decoherence observed for ground-state excitons in two-dimensional semiconductors. This robustness to imperfections suggests a promising approach to quantum photonics at the level of individual photons.