Publications by Ursula Oesterle

Chat with Graph Search

Ask any question about EPFL courses, lectures, exercises, research, news, etc. or try the example questions below.

DISCLAIMER: The Graph Chatbot is not programmed to provide explicit or categorical answers to your questions. Rather, it transforms your questions into API requests that are distributed across the various IT services officially administered by EPFL. Its purpose is solely to collect and recommend relevant references to content that you can explore to help you answer your questions.

We do not intend to give here a background knowledge on vacuum field Rabi splitting. The reader should refer to J.M. Raimond, T. Norris, H. Yokoyama and D.S. Citrin lecture notes. For the sake of completeness we simply remind the reader that the cavity quantum electrodynamics (CQED) treatment of a two level atomic system resonantly coupled to a single photon mode predicts that the eigenstates of the system are no longer the photon and atomic oscillator states but two mixed symmetric and anti symmetric state

In this paper, we present a systematic study of the effect of growth parameters on the structural and optical properties of InAs quantum dot (QD) grown under Stranski-Krastanov mode by molecular beam epitaxy. The dot density is significantly reduced from 1.9x10(10) to 0.6x10(10) cm(-2) as the growth rate decreases from 0.075 to 0.019 ML/s, while the island size becomes larger. Correspondingly, the emission wavelength shifts to the longer side. By increasing the indium fraction in the InGaAs capping layer, t

We investigate a GaAs/(Ga,Al)As Fabry-Perot microcavity, into which (In,Ga)As quantum wells have been inserted. The cavity is wedge shaped, i.e., the detuning between the bare-exciton resonance and the bare optical cavity mode depends on the spatial position on the sample. Linear transmission spectra reveal a well-resolved Rabi splitting of 8 meV at resonance, an inhomogeneously broadened exciton transition of 4-5-meV width, and an 0.7-meV-wide Fabry-Perot mode. The time-resolved transmission exhibits deep

In a pump-probe experiment, we have been able to control, with phase-locked probe pulses, the ultrafast nonlinear optical emission of a semiconductor microcavity, arising from polariton parametric amplification. This evidences the coherence of the polariton population near k = 0, even for delays much longer than the pulse width. The control of a large population at k = 0 is possible although the probe pulses are much weaker than the large polarization they control. With rising pump power the dynamics of the

We study the subpicosecond gain dynamics in a high-finesse semiconductor microcavity containing quantum wells by means of degenerate pump-probe spectroscopy. Tuning the optical excitation in resonance with both the exciton and the cavity modes, at high pump fields the probe pulses are strongly amplified near the energy of the empty-cavity mode. At zero probe delay, integration of the probe spectrum yields a net gain of several percents. The coherent nature of the gain is demonstrated by its oscillatory beha

We report transient sub-picosecond pump and probe experiments performed on a semiconductor microcavity into which quantum wells have been inserted. The cavity is featuring resonance and strong coupling with the exciton. It is strongly and resonantly excited. Optical amplification of the probe beam (up to a factor of 5) appears, a blueshift of the polaritons occurs once the excitation reaches the exciton saturation density. The intensity of the probe, reflected or transmitted by the sample, oscillates while

High-efficiency top-emitting InGaAs/AlGaAs microcavity light-emitting diodes (MCLEDs) have been optimized and fabricated. The structures were grown using molecular beam epitaxy on GaAs substrates. They consist of a three-period Be-doped distributed Bragg reflector (DBR) centred at 950 nm wavelength, a cavity containing three InGaAs quantum wells and a 15-period Si-doped DBR. Different values for the wavelength detuning between the spontaneous emission line and Fabry-Perot cavity mode were explored, between

We present here measurements on hexagonal cavities that have areas between 2.0 and 8.6 mu m/sup 2/. The 2D triangular lattice PBG mirrors are etched into a GaAs/AlGaAs waveguide heterostructure with 3 layers of InAs quantum dots at the centre of a 240 nm thick GaAs core. The photoluminescence of the InAs dots internally probes the cavity resonances and the small fraction of light that is scattered into air is collected and fed to an optical multichannel analyser. The hexagonal cavities defined by 2D photoni

It is demonstrated that during the first few picoseconds after resonant femtosecond excitation the secondary radiation from a strongly coupled semiconductor microcavity containing one quantum well is dominated by Rayleigh scattered light. At early times after excitation (10 ps) the lower polariton branch provides the most intense emission which is due to incoherent luminescence.

We investigate the mechanisms leading to the optical non-linearities observed on a strongly excited semiconductor microcavity containing quantum wells. This study of a coupled exciton-cavity system is possible owing to the availability of a sample of exceptionally high quality, permitting to exclude effects of disorder and inhomogeneous broadening. Sub-picosecond pump and probe experiments are performed, in the regime of an incoherent exciton gas of high density. For such a gas the dephasing due to collisio

The use of photonic crystals (PCs) for realistic light emitting diodes (LEDs) is discussed, given the constraints of planar semiconductor technology. A viable route for the fabrication of high-efficiency high-brightness electrically injected LEDs is presented. The starting point is a top-emitting microcavity using a single Alox Bragg mirror. The active area is surrounded by two-dimensional PCs, namely arrays of air rods etched through the top layers; injection of the electrons is achieved through the crysta

We report on the optical response of a semiconductor microcavity featuring a strong exciton-photon coupling. The weak excitation regime is investigated experimentally by means of time-resolved transmission and four-wave mixing experiments. The influence of electronic disorder on the coherent exciton-photon dynamics is discussed in terms of tl-ie solutions of the Maxwell-Bloch equations. The high excitation regime is investigated by using transient sub-picosecond pump-probe experiments. Optical amplification

We present femtosecond gain measurements in microcavity-embedded quantum wells. When the excitonic transition is saturated by an intense pump field, the spectrum measured with a weak probe pulse is strongly modulated by pump-probe wave mixing processes. A giant probe amplification occurs within the bandwidth of the empty-cavity mode. The optical feedback provided by the microcavity is responsible for a net gain of the broadband probe pulse. [S0163-1829(99)50424-4].

We demonstrate edge-emitting lasers based on self-assembled InAs quantum dots (QDs) on GaAs substrates. The InAs QDs are embedded in an InGaAs quantum well (QW) to red-shift the lasing transition. The lasers emit at lambda=1.2 mum with threshold current densities approximate to100 A/cm(2). Maximum modal gains on the order of 5 cm(-1) are deduced for a single QD sheet.

The coherent dynamics of cavity-polaritons are investigated using the four-wave-mixing technique. A series of experiments on four samples operating in both the weak and strong coupling regimes were performed to study the influence of strong coupling on the interaction of cavity-polaritons with other cavity-polaritons, free carriers and acoustic phonons. Due to Rabi splitting a larger number of free carriers are created in the strong coupling sample compared with the weak coupling sample. This has a signific

We report femtosecond pump and probe experiments in a semiconductor microcavity containing quantum wells. At high pump fields, the exciton-polariton Rabi doublet changes into a triplet structure. The triplet splitting increases as the square root of the input intensity. The transmitted probe intensity is modulated with the corresponding frequency Versus pump-probe delay. The experimental results are discussed in terms of Mollow spectra of a saturated transition of a two-level system.

The coherent optical response of high quality microcavities containing quantum wells is investigated. The dynamics of the ac Stark effect is investigated by degenerate pump-probe experiments, by exciting the quantum well excitons at various intensities and detunings. The evolution from a simple dynamical excitonic Stark shift to a splitting is dearly observed, even when the excitation is degenerate with the continuum states. The experimental results agree well with the predictions of a theoretical model bas

A dramatic suppression of the absorption of light by exciton polaritons is observed after resonant excitation of the polaritonic modes in a multiple quantum well Bragg structure. Time-resolved reflectivity measurements confirm that this is due to the formation of a dominant superradiant polariton mode created by the light-induced coupling of excitons in different quantum wells that suppress absorption. The stability of the superradiant mode is demonstrated at high excitation powers and at temperatures of up

Regular periodic structures with large refractive index contrast are often called photonic crystals and may exhibit photonic bandgap behaviour. Planar waveguide 2D and 1D periodic microstructures exhibiting photonic bandgap behaviour are likely to be useful in realising the devices and connecting structures required for compact forms of integrated optical circuit.

We report novel oscillator strength transfer phenomena induced by the exciton-exciton correlation. A high quality semiconductor microcavity is resonantly excited by intense circularly polarised sigma(+) pump pulses (100 fs long) and probed at different delays by weak counter-polarised sigma(-) test pulses. We show that the presence of sigma(+) excitons can completely inhibit the creation of sigma(-) excitons. With increasing sigma(+) exciton density the oscillator strength of the a- transition is transferre

Ursula Oesterle

Chat with Graph Search

Vacuum field Rabi splitting in a semiconductor microcavity

Tuning InAs/GaAs quantum dot properties under Stranski-Krastanov growth mode for 1.3 mu m applications

Coherent exciton-photon dynamics in semiconductor microcavities: The influence of inhomogeneous broadening

Coherent control of polariton parametric scattering in semiconductor microcavities

Net coherent optical gain in strongly pumped semiconductor microcavities

Optical stark effect and coherent gain of excitons in a semiconductor microcavity

Design and characterization of top-emitting microcavity light-emitting diodes

Directional effects in photonic bandgap cavities

Resonant Rayleigh scattering versus incoherent luminescence in semiconductor microcavities

Intrinsic non-linearities in exciton-cavity-coupled systems

High extraction efficiency, laterally injected, light emitting diodes combining microcavities and photonic crystals

Exciton-photon dynamics in weakly and strongly excited semiconductor microcavities

Strong coherent gain from semiconductor microcavities in the regime of excitonic saturation

Long-wavelength edge-emitting lasers on gallium arsenide using InAs quantum dots embedded in InGaAs

Dephasing of strongly coupled exciton-photon systems

Strongly driven semiconductor microcavities: From the polariton doublet to an AC Stark triplet

The microcavity AC Stark triplet: Excitation in the exciton continuum

Suppression of exciton-polariton light absorption in multiple quantum well Bragg structures

Waveguide photonic crystals and microstructures

Crossover from exciton to biexciton cavity polaritons