Abstract
We report a systematic study of the temperature and excitation density behavior of an AlAs/AlGaAs, vertically emitting microcavity with embedded ternary Al0.20Ga0.80As/AlAs quantum wells in the strong coupling regime. Temperature-dependent photoluminescence measurements of the bare quantum wells indicate a crossover from the type-II indirect to the type-I direct transition. The resulting mixing of quantum well and barrier ground states in the conduction band leads to an estimated exciton binding energy systematically exceeding 25 meV. The formation of exciton-polaritons is evidenced in our quantum well microcavity via reflection measurements with Rabi splittings ranging from (13.93 ± 0.15) meV at low temperature (30 K) to (8.58 ± 0.40) meV at room temperature (300 K). Furthermore, the feasibility of polariton laser operation is demonstrated under non-resonant optical excitation conditions at 20 K and emission around 1.835 eV.
Highlights
Strong coupling between microcavity photons and quantum well (QW) excitons leads to the generation of new quasi-particles with a hybrid light-matter character named exciton-polaritons
3.1 Temperature-dependent determination of the Rabi splitting As a first step, we confirm that strong coupling persists at room temperature by measuring the anti-crossing of QW exciton and cavity photon modes in temperature-dependent white-light reflection measurements
The arrows indicate the position of the individual polariton branches which we identify as the lower (LP), middle (MP) and the upper (UP) polariton
Summary
Strong coupling between microcavity photons and quantum well (QW) excitons leads to the generation of new quasi-particles with a hybrid light-matter character named exciton-polaritons (polaritons). The Al-concentration of the QW itself can be used as another adjusting parameter by changing the QW material to AlGaAs which opens the way to a completely new energy range for GaAs/AlGaAs based polariton systems well up to ~ 2.0 eV Those structures are highly suitable for strong coupling with commonly used transition metal dichalcogenide monolayers [29,30] and fluorescent proteins [31] in hybrid cavity approaches. Calculations of the band diagram and temperature-dependent photoluminescence measurements of the bare quantum wells indicate a crossover from the type-II indirect to the type-I direct transition as well as exciton binding energies exceeding 25 meV, being necessary for stable excitons at room temperature. The structure can be optimized for room temperature, by adjusting the width of the barrier and the QW and shifting the emission energy
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