Observation of the transition from lasing driven by a bosonic to a fermionic reservoir in a GaAs quantum well microcavity

We show that by monitoring the free carrier reservoir in a GaAs-based quantum well microcavity under non-resonant pulsed optical pumping, lasing supported by a fermionic reservoir (photon lasing) can be distinguished from lasing supported by a reservoir of bosons (polariton lasing). Carrier densities are probed by measuring the photocurrent between lateral contacts deposited directly on the quantum wells of a microcavity that are partially exposed by wet chemical etching. We identify two clear thresholds in the input-output characteristic of the photoluminescence signal which can be attributed to polariton and photon lasing, respectively. The power dependence of the probed photocurrent shows a distinct kink at the threshold power for photon lasing due to increased radiative recombination of free carriers as stimulated emission into the cavity mode sets in. At the polariton lasing threshold on the other hand, the nonlinear increase of the luminescence is caused by stimulated scattering of exciton-polaritons to the ground state which do not contribute directly to the photocurrent.PostprintPeer reviewe

Site-controlled InAs/GaAs quantum dots emitting at telecommunication wavelength

This work was financially supported by the German Ministry of Education and Research (BMBF) via the project QuaHL-Rep and by the State of Bavaria.We demonstrate site-controlled InAs/GaAs quantum dot (QD) emission at 1.3 mu m telecommunication wavelength. The samples were fabricated by molecular beam epitaxy on patterned substrates, which have been prepared by electron beam lithography and wet chemical etching. By embedding a single layer of positioned QDs in a strain reducing InGaAs quantum well layer, we successfully shifted the emission band beyond the important telecommunication wavelength of 1.3 mu m. Furthermore, the resulting deep carrier confinement allowed us to preserve strong QD luminescence up to room temperature.PostprintPeer reviewe

Low dimensional GaAs/air vertical microcavity lasers

This work was financially supported by the state of Bavaria and the bilateral project of the Deutsche Forschungsgemeinschaft (Project LIEPOLATE) and the Polish Ministry of Science and higher education (Project No. DPN/N99/DFG/2010).We report on the fabrication of gallium arsenide (GaAs)/air distributed Bragg reflector microresonators with indium gallium arsenide quantum wells. The structures are studied via momentum resolved photoluminescence spectroscopy which allows us to investigate a pronounced optical mode quantization of the photonic dispersion. We can extract a length parameter from these quantized states whose upper limit can be connected to the lateral physical extension of the microcavity via analytical calculations. Laser emission from our microcavity under optical pumping is observed in power dependent investigations.Publisher PDFPeer reviewe

Site-controlled growth of InP/GaInP quantum dots on GaAs substrates

A technology platform for the epitaxial growth of site-controlled InP quantum dots (QDs) on GaAs substrates is presented. Nanoholes are patterned in a GaInP layer on a GaAs substrate by electron beam lithography and dry chemical etching, serving as QD nucleation centers. The effects of a thermal treatment on the structured surfaces for deoxidation are investigated in detail. By regrowth on these surfaces, accurate QD positioning is obtained for square array arrangements with lattice periods of 1.25 mu m along with a high suppression of interstitial island formation. The optical properties of these red-emitting QDs (lambda similar to 670 nm) are investigated by means of ensemble-and micro-photoluminescence spectroscopy at cryogenic temperatures.</p