Despite their name polariton lasers do not rely on stimulated emission of cavity photons. The less stringent threshold conditions are the cause that bosonic polariton lasers can outperform standard lasers in terms of their threshold currents. The part-light and part-matter quasiparticles called polaritons, can undergo a condensation process into a common energy state. The radiated light from such a system shares many similarities with the light emitted from a conventional photon laser, even though the decay of the polaritons out of the finite lifetime cavity is a spontaneous process. We discuss properties of polariton condensates in GaAs based microcavities. The system’s response to an external magnetic field is used as a reliable tool to distinguish between polariton laser and conventional photon laser. In particular, we will discuss the realization of an electrically pumped polariton laser, which manifests a major step towards the exploitation of polaritonic devices in the real world.
Polariton Lasers do not rely on stimulated emission of photons, a criterion that sets stringent conditions on the threshold current in a conventional laser. Therefore, they have the capability to outperform photon lasers in the weak coupling regime in terms of the threshold power consumption. We present the first successful realization of an electrically pumped polariton laser based on a GaAs/AlAs distributed Bragg reflector cavity. We have furthermore identified the system’s response to an applied magnetic field as a sensitive tool to distinguish a polariton laser from a standard VCSEL device in the weak light-matter coupling regime
We study the system with dipolaritons - mixed quasiparticles which are formed in the double quantum well
heterostructure in the presence of strong light-matter interaction. These quasiparticles possess large dipole
moment due to the resonant coupling between direct and indirect excitons via electronic tunnelling. Using the
pulsed pumping of the cavity mode one can induce oscillations of the indirect exciton density. This corresponds
to a harmonic change of the dipole moment in time and results in the classical electromagnetic wave emission
with frequency being in the terahertz (THz) range. In the current paper we present a simple theory which
describes this phenomenon and estimate possible output power of radiation.
A system where a Bose-Einstein condensate of exciton-polaritons coexists with a Fermi gas of electrons has been recently proposed as promising for realization of room-temperature superconductivity. In order to find the optimum conditions for exciton and exciton-polariton mediated superconductivity, we studied the attractive mechanism between electrons of a Cooper pair mediated by the exciton and exciton-polariton condensate. We also analyzed the gap equation that follows. We specifically examined microcavities with embedded n-doped quantum wells as well as coupled quantum wells hosting a condensate of spatially indirect excitons, put in contact with a two-dimensional electron gas. An effective potential of interaction between electrons was derived as a function of their exchanged energy ℏω, taking into account the retardation effect that allows two negatively charged carriers to feel an attraction. In the polariton case, the interaction is weakly attractive at long times, followed by a succession of strongly attractive and strongly repulsive windows. Strikingly, this allows high critical temperature solutions of the gap equation. An approximate three-steps potential is used to explain this result that is also obtained numerically. The case of polaritons can be compared with that of excitons, which realize the conventional scenario of high-Tc superconductivity where a large coupling strength accounts straightforwardly for the high critical temperatures. Excitons are less advantageous than polaritons but may be simpler systems to realize experimentally. It is concluded that engineering of the interaction in these peculiar Bose-Fermi mixtures is complex and sometimes counter-intuitive, but leaves much freedom for optimization, thereby promising the realization of high-temperature superconductivity in multilayered semiconductor structures.
In 2004 two groups have reported observation of the strong coupling regime in 3D microcavities with single quantum dots (QD). We present the quantum theory of non-linear emission of photons by such structures. We derive the exciton creation operator which coincides with a Fermi one for QDs smaller than the exciton Bohr radius and with Bose one for very large QDs. In intermediate size dots excitonic statistics is in between the Fermi and Bose ones. Consequently, the non-linear optical spectra change from the Mollow triplet in the fermionic case to the Rabi doublet in the bosonic case. We predict appearance of a characteristic multiplet structure of the non-linear emission in the intermediate regime.