Exciton-photon dynamics in weakly and strongly excited semiconductor microcavities

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Fibers doped with bismuth show broad luminescence bands around 750, 1100, and 1400 nm with spectral bandwidths of 100 to 200 nm at room temperature. The luminescence bands can be observed by pumping broad absorption bands in the visible or near infrared spectrum (around 500, 700, 800, 1000, and 1360 nm). Bismuth fiber laser action has been demonstrated using FBG in standard germanosilicate fibers as intra-core laser mirrors. In this work we report about the investigation of refractive index and luminescence

We demonstrate 2-mu m wavelength, wafer-fused InGa(Al)As/InP-AlGaAs/GaAs vertical-cavity surface-emitting lasers (VCSELs) emitting single-mode power of 0.5 mW at room-temperature with a threshold current of 4mA and side-mode suppression ratio of over 30 dB. Emission wavelength can be continuously tuned with current by similar to 5 nm without mode hopping with a tuning rate of 0.31 nm/mA. These features demonstrate the long wavelength VCSELs potential for gas sensing and other optical spectroscopy applicatio

We present a theoretical model of the time-resolved excitonic photoluminescence in quantum wires. We study the role of disorder and of the exciton-free-carrier interaction on the temperature dependence of the photoluminescence lifetime. We find that at low temperature the exciton population is not thermalized in disordered quantum wires and that the lifetime is mainly determined by the localization length of the exciton. However, for large localization lengths or high enough temperatures the exciton populat

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

An optical modulator is arranged to compensate for the thermo-optical modulating effects induced by charge-injection based phase modulators. It comprises first modulator means (3), that receive optical radiation (11, 21), direct it along an optical path, apply a first predetermined optical phase modulation by the injection of free charges into the optical path, and output optical radiation (13, 22) so modulated. Compensator means (4) apply, to optical radiation output from (13, 22), or to be received by, th

We have directly measured, under operating conditions, the distributions of carrier densities and temperatures in a gain-clamped semiconductor optical amplifier designed for operation at 1.55 mum. As expected, longitudinal spatial hole burning is much smaller than in conventional semiconductor optical amplifiers and the effects of gain clamping are clearly evidenced. The amplifier nevertheless shows a sizeable temperature increase for both the lattice and the carriers at high currents, which are attributed

Using time-resolved photoluminescence, we have investigated the radiative behavior of neutral and negatively charged excitons in CdTe-based quantum wells. We find that the photoluminescence of negatively charged excitons can be well reproduced by a model of delocalized and thermalized three-particle complexes. A large radiative zone in k-space results from the transfer of the charged exciton momentum to the remaining electron (recoil effect). On the other hand, the photoluminescence decay of excitons is not

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

The role of the confinement potential symmetry on the electronic and optical properties of quantum mires is systematically studied. In a wide class of quantum mires with mirror symmetry we evidence a new set of optical transitions resulting both from band mixing and Ct, symmetry breaking at zone center. Several kinds of quasi-one-dimensional excitons are predicted as well as their specific dipole coupling. Even for ultralow C-1 symmetry we find independent excitons with distinct polarization selection rules

The time-resolved secondary emission of resonantly created excitons in GaAs quantum wells is studied using femtosecond up-conversion spectroscopy. The behaviour of the rise and decay of the secondary emission and reflectivity in quantum welts is strongly dependent upon the disorder at the interfaces, the exciton density and the temperature. In the case of low densities and temperatures the emission is independent of the exciton density and rises quadratically in time, in excellent agreement with recent theo

Transitions from bound atomic Rydberg Stark states in a static electric field to autoionizing Rydberg states above the electric-field-induced ionization threshold are studied using a broadband, tunable free-electron laser (photon energy 160-1400 cm(-1), pulse duration similar to 1 ps) and compared with multichannel quantum defect theory calculations. An atomic streak camera is used to record the time-resolved electron emission transients of the autoionizing atoms. For Stark states located on the downfield s

We use a rate equation model in order to reproduce the dynamics of two-dimensional excitons and free carriers in a time resolved photoluminescence experiment. We investigate the dynamics of the exciton formation from free electron-hole pairs, and the evolution of Is excitons within their band. The interaction of excitons and free carriers with optical and acoustic phonons is considered. The shape of the time resolved photoluminescence signal is considerably different in the case of acoustic or optical phono

An automated assembly technique for small optical components has been developed. It concerns components such as, e.g., laser diodes and LEDs, fibers, lenses, beamsplitters, polarizers, mirrors, crystals, prisms, diffractive elements or photodiodes. It is based on the flexible 2-dimensional arrangement of an universal tripod holder (10 x 10 x 4 mm) on a planar mounting plate. Its particular mechanical structure allows to align the optical elements on-line and to attach them to the mounting plate in a one ste

The optical nonlinearity of a GaAs/AlAs periodic layered structure was experimentally investigated for the first time. The shift of the reflectivity peak with increasing intensity was observed. A reflectivity contrast of about 10:1 was obtained by varying the incident intensity. Hysteresis loops due to the response delay of both the electronic and the thermal nonlinearity were observed. All-optical logic operations were also demonstrated. A further improvement of the structure may lead to a new type of opti

Exciton-photon dynamics in weakly and strongly excited semiconductor microcavities

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ArF laser induced refractive index and luminescence changes in Bi-doped aluminosilicate fibers - INVITED

2-μm wavelength range InGa(Al)As/InP-AlGaAs/GaAs wafer fused VCSELs for spectroscopic applications

Modeling the photoluminescence lifetime in realistic quantum wires

Coherent control of polariton parametric scattering in semiconductor microcavities

An optical modulator

Density clamping and longitudinal spatial hole burning in a gain-clamped semiconductor optical amplifier

Negatively charged excitons in CdTe-based quantum wells: A time-resolved study

Net coherent optical gain in strongly pumped semiconductor microcavities

The impact of low symmetry on the electronic and optical properties of quantum wires

Femtosecond dynamics of secondary radiation formation from quantum well excitons

Decay of oriented Rydberg wave packets excited with far-infrared radiation

Photoluminescence and carrier dynamics in GaAs quantum wells

Flexible automated assembly of micro-optical elements (optical SMD)

All-Optical Reflectivity Tuning and Logic Gating in a GaAs/AlAs Periodic Layered Structure