The phenomenon of cooperative spontaneous emission (Dickepsilas superradiance) is investigated numerically for ensembles of strongly-confined quantum dots coupled to low-Q optical cavities. Clear signatures of superradiance are predicted for emission dynamics and photon statistics.
The collective spontaneous emission of a fully inverted inhomogeneously broadened ensemble of N two-level systems coupled to a single-mode low-Q cavity is investigated numerically using Monte Carlo wave function technique. An intrinsically bi-exponential emission dynamics is found when the time scales of superradiance tau(sr) and inhomogeneous dephasing T2* approximately 1/Deltaomega(inh) become comparable: a fast superradiant is followed by a slow subradiant decay. Experimental configurations using ensembles of quantum dots coupled to optical microcavities are proposed as possible candidates to observe the combined superradiant and subradiant energy relaxation.
Emission spectra of quantum dot arrays in zero-dimensional microcavities are studied theoretically. It is shown that their form is determined by the competition between collective superradiant mode formation and inhomogeneous broadening. A random sources method is used to calculate the photoluminescence spectra from an nonresonant pumped microcavity, and a standard diagram technique is used to provide a microscopic justification for the random sources method. The emission spectra of a microcavity are analyzed taking into account the spread of exciton energy due to inhomogeneous distribution of quantum dots and tunneling between them. It is demonstrated that the luminescence spectra of strongly tunnel-coupled quantum dots are sensitive to the dot positions, and the collective mode can (under certain conditions) be stabilized by random tunneling links.
Quantum cooperativity is evident in light-matter platforms where quantum emitter ensembles are interfaced with confined optical modes and are coupled via the ubiquitous electromagnetic quantum vacuum. Cooperative aspects such as dipole-dipole interactions and subradiance find applications in the design of nanoscale coherent light sources and highly-reflective quantum metasurfaces made up of hundreds of optically trapped atoms, in the implementation of topological quantum optics on subwavelength arrays of emitters, in quantum metrology and quantum information. The quick bursts of radiation from a collection of quasi-indistiguishable emitters provides an alternative approach to standard lasers by introducing superradiant lasers operating at extremely low intracavity power. This tutorial provides a set of theoretical tools to tackle the behavior responsible for the onset of cooperativity in light-matter systems by extending open quantum system dynamics methods, such as the master equation and quantum Langevin equations, to electron-photon interactions in strongly coupled and correlated quantum emitters ensembles. These analytical approaches are then also extended to frequency disordered or vibronically coupled quantum emitter ensembles with wide relevance ranging from atoms in optical lattices, quantum dots in solid state environments or molecular quantum systems.
Superradiance (SR), or cooperative spontaneous emission, has been predicted by R. Dicke before the invention of the laser. During the last few years one can see a renaissance of both experimental and theoretical studies of the superradiant phase transition in a variety of media, ranging from quantum dots and Bose condensates through to black holes. Until recently, despite of many years of research, SR has been considered as a phenomenon of pure scientific interest without obvious potential applications. However, recent investigations of the femtosecond SR emission generation from semiconductors have opened up some practical opportunities for the exploitation of this quantum optics phenomenon. Here we present a brief review of some features, advantages and potential applications of the SR generation from semiconductor laser structures
Cooperative effects such as super(or sub)radiance in quantum systems arise from the interplay among quantum emitters. While bright superradiant states have been extensively studied and have yielded important insights into cooperative phenomena, subradiant states remain less explored due to their inherently dark state nature. However, subradiance holds significant potential as a valuable quantum resource exploiting long-lived and large-scale entanglement, which is a key for advancing quantum information technologies. Here, we demonstrate strong collective emission from a cavity-mediated steady-state subradiant state. In a tailored photonic environment with balanced cavity dissipation, emitter-field coupling strength, and incoherent pumping, two quantum dots coupled to a low-Q cavity exhibit a steady-state population in a subradiant state with a highly negative cooperativity parameter among the emitters. As a key signature of steady-state subradiance, the system shows strong photon bunching ( g(2)(0)>8 ) and suppressed single-photon decay (36 ns). Furthermore, we investigate that such collective interactions can be manipulated by controlling various system parameters, such as detuning and dephasing, supported by numerical simulations. Our approach to inducing cavity-mediated subradiance paves the way for generating and harnessing quantum correlations among quantum emitters via controlled dissipation. Subradiance is a cooperative effect in systems of quantum emitters, which is the opposite of superradiance, or enhanced emission, but has been less explored. Here, the authors demonstrate a steady-state subradiant state in a system of two InAs quantum dots coupled to a low-Q nanophotonic cavity.