Abstract
Light is often characterized only by its classical properties, like intensity or coherence. When looking at its quantum properties, described by photon correlations, new information about the state of the matter generating the radiation can be revealed. In particular the difference between independent and entangled emitters, which is at the heart of quantum mechanics, can be made visible in the photon statistics of the emitted light. The well-studied phenomenon of superradiance occurs when quantum–mechanical correlations between the emitters are present. Notwithstanding, superradiance was previously demonstrated only in terms of classical light properties. Here, we provide the missing link between quantum correlations of the active material and photon correlations in the emitted radiation. We use the superradiance of quantum dots in a cavity-quantum electrodynamics laser to show a direct connection between superradiant pulse emission and distinctive changes in the photon correlation function. This directly demonstrates the importance of quantum–mechanical correlations and their transfer between carriers and photons in novel optoelectronic devices.
Highlights
Light is often characterized only by its classical properties, like intensity or coherence
Most prominent is the transition of the time dynamics from the exponential decay of independent emitters to superradiant pulse emission as a result of collectiveemitter decay[3], most experiments resort to decay-time changes as function of the emitter number
We have identified three independent signatures of dominating inter-emitter coupling, which determine the emission properties below threshold and in the threshold region for pulsed optical pump excitation: superradiant pulse emission with a temporal duration more than one order of magnitude faster than the spontaneous lifetime of individual emitters, giant photon bunching in the second-order photon correlation function gð2Þðt1⁄40Þ strongly exceeding the value of two for thermal light, and excitation trapping suppressing the emission by almost two orders of magnitude as long as the correlations between the emitters are present
Summary
Light is often characterized only by its classical properties, like intensity or coherence. Thermal radiation is found in the uncorrelated spontaneous recombination of independent emitters Quantum mechanically, this type of light can be distinguished from coherent (above threshold) laser emission or the more exotic nonclassical light states using the second-order photon correlation function, gð2Þðt1⁄40Þ. Despite being an extensively studied phenomenon[3,4] observed in a variety of systems, including semiconductor quantum dots[5,6], practically all demonstrations of superradiance so far rely on macroscopic properties: changes of the time-resolved intensity or linewidth of the emitted radiation. In this work we demonstrate that radiative emitter coupling can dramatically change the statistical properties of the light emission These changes provide a more direct way to study the quantum–mechanical inter-emitter correlations driving the superradiance and the underlying physics of the collective decay. The latter has been confirmed subsequently in ref. 8, while experimental demonstrations of the enhanced photon bunching have been missing so far
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