Marc Aßmann

Higher-Order Photon Bunching in a Semiconductor Microcavity

A Multiple Photon Pileup The field of quantum optics began with the observation that two independent photons emitted from a thermal source tend to bunch together. The same is true for any number of bosons, but how do the statistics and correlations evolve experimentally as the number increases? Aβmann et al. (p. 297) have developed a streak-camera technique that can distinguish the photon number and measure the higher-order correlations between the photons at the detector. The results confirm the predicted “n factorial” dependence, showing that the tendency to bunch gets stronger as the number of independent photons is increased. The tendency for photons to bunch gets stronger as their number increases. Quantum mechanically indistinguishable particles such as photons may show collective behavior. Therefore, an appropriate description of a light field must consider the properties of an assembly of photons instead of independent particles. We have studied multiphoton correlations up to fourth order in the single-mode emission of a semiconductor microcavity in the weak and strong coupling regimes. The counting statistics of single photons were recorded with picosecond time resolution, allowing quantitative measurement of the few-photon bunching inside light pulses. Our results show bunching behavior in the strong coupling case, which vanishes in the weak coupling regime as the cavity starts lasing. In particular, we verify the n factorial prediction for the zero-delay correlation function of n thermal light photons.

Giant photon bunching, superradiant pulse emission and excitation trapping in quantum-dot nanolasers

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.

From polariton condensates to highly photonic quantum degenerate states of bosonic matter

Bose–Einstein condensation (BEC) is a thermodynamic phase transition of an interacting Bose gas. Its key signatures are remarkable quantum effects like superfluidity and a phonon-like Bogoliubov excitation spectrum, which have been verified for atomic BECs. In the solid state, BEC of exciton–polaritons has been reported. Polaritons are strongly coupled light-matter quasiparticles in semiconductor microcavities and composite bosons. However, they are subject to dephasing and decay and need external pumping to reach a steady state. Accordingly the polariton BEC is a nonequilibrium process of a degenerate polariton gas in self-equilibrium, but out of equilibrium with the baths it is coupled to and therefore deviates from the thermodynamic phase transition seen in atomic BECs. Here we show that key signatures of BEC can even be observed without fulfilling the self-equilibrium condition in a highly photonic quantum degenerate nonequilibrium system.

Exciton and trion dynamics in atomically thin MoSe2 and WSe2: effect of localization

We present a detailed investigation of the exciton and trion dynamics in naturally doped

Quantum chaos and breaking of all anti-unitary symmetries in Rydberg excitons

{\mathrm{MoSe}}_{2}

Observation of High Angular Momentum Excitons in Cuprous Oxide.

and

Deviations of the exciton level spectrum in cuprous oxide from the hydrogen series

{\mathrm{WSe}}_{2}

Measuring the dynamics of second-order photon correlation functions inside a pulse with picosecond time resolution

single atomic layers as a function of temperature in the range 10--300 K under above band-gap laser excitation. By combining time-integrated and time-resolved photoluminescence (PL) spectroscopy, we show the importance of exciton and trion localization in both materials at low temperatures. We also reveal the transition to delocalized exciton complexes at higher temperatures where the exciton and trion thermal energy exceeds the typical localization energy. This is accompanied by strong changes in PL including suppression of the trion PL and decrease of the trion PL lifetime, as well as significant changes for neutral excitons in the temperature dependence of the PL intensity and the appearance of a pronounced slow PL decay component. In

Temperature dependence of pulsed polariton lasing in a GaAs microcavity

{\mathrm{MoSe}}_{2}

Scaling laws of Rydberg excitons

and