Intersubband Polaritons stems from the strong coupling interaction between the confined electronic states within the the conduction band of quantum wells and a photonic microcavity resonant mode. The formed quai-particles are at the heart of several intriguing physical phenomenon such as final state stimulation or the emission of correlated photon pairs. The following research activities aim at developping innovative optoelectronic devices based on the aforementioned meachanisms.
The aim of this project is to explore the bosonicity of intersubband polaritons in order to demonstrate a final state stimulation mechanism under optical injection of light. We have developped over the years a pratical microcavity system hosting intersubband polaritons Fig1 (a). Under resonant injection of light, we explore the scattering mechanism between the two polaritonic states exploiting the inherent dispersive nature of these quasi-particles Fig 1(b). We have recently demonstrated the existence of a scattering mechanism via LO phonons between the injection and final states of this system Fig 1(c). This first demonstration of spontaneous emission in ISB polaritonic device paves the way towards the demonstration of a polaritonic laser. The bosonic nature of ISB polaritons predicts that they can be subject to final state stimulation. When the density of polaritons n1 goes above the critical density, the scattering rate grows with the density n1+1 leading to an exponential increase of the final state polariton density. Hence photons escape the microcavity under a coherent form which can be seen for an external observer as laser light.
Figure 1: (a) MIM micro-cavity system used to obtain the strong coupling regime. (b) Dispersion curve and scattering mechanism used to emit light in ISB polaritonic systems. (c) Experimental observation of the spontaneously emitted light under resonant optical injection
See: Resonant intersubband polariton-LO phonon scattering in an optically pumped polaritonic device,
Applied Physics Letters 112, 191106 (2018).
Perspectives for Intersubband Polariton Lasers. Physical Review X 5, 011031 (2015)
The aim of this project is to modulate on an ultrafast scale the polaritons population and in turn study in the time domain their construction and emission properties. Depending on the frequency range that we explore, we have developp several micro-cavity systems that allow us to either modulate the light or the matter part of the polaritons. In the THz range, we are exploiting the circuital nature of LC resonator to implement switching functionnalities as depicted on Fig 2(a), allowing a direct modulation of optical density os states within the microcavity. Within the Mid IR range, we have devlopp a MIM cavity with a transparent substrate which allows a direct modulation of the electronic density within the system Fig 2(b).
Figure 2: (a) Schematic of the LC microcavity switch and its equivalent circuit. The substrate semiconductor is photo-activated on a fs time scale to change the microcavity resonance frequency. (b) Schematic of the Mir MIM cavity on a transparent substrate, allowing a direct homogeneous excitation of the AR.
See: Sub-cycle switch-on of ultrastrong light-matter interaction,
Nature 458, 178-181 (2009)
Optically Implemented Broadband Blueshift Switch in the Terahertz Regime, Physical Review Letters 106, 037403 (2011)