Purcell effect for CdSe∕ZnSe quantum dots placed into hybrid micropillars (original) (raw)
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Applied Physics Letters, 2012
The coupling of CdTe/ZnTe quantum dot (QD) emission to micropillar cavity eigenmodes in the weak coupling regime is demonstrated. We analyze photoluminescence spectra of QDs embedded in monolithic micropillar cavities based on Bragg mirrors which contain MgSe/ZnTe/MgTe superlattices as low-index material. The pillar emission shows pronounced cavity eigenmodes and their spectral shape is in good agreement with simulations. QD emission in resonance with the cavity mode is shown to be efficiently guided toward the detector and an experimental Purcell enhancement by a factor of 5.7 is determined, confirming theoretical expectations.
Purcell effect on CdSe/ZnSe quantum dots em bedded in pillar microcavities
physica status solidi (c), 2005
We present results on two approaches for placing II-VI quantum dots in resonance with a pillar microcavity. The first approach consists in growing a fully epitaxial structure: a ZnTe 3λ/2 cavity containing CdTe quantum dots sandwiched between two CdMgTe/CdZnMgTe distributed Bragg reflectors. We observed a strong enhancement of the emission intensity for a dot well located into a 0.9 µm diameter pillars. More striking results were obtained using CdSe QDs in a λ/2 ZnSe cavity sandwiched between SiO2/T iO2 Bragg reflectors. We probed the Purcell effect by time-resolved photoluminescence and intensity saturation measurements performed on single quantum dots located in a 1.1 µm diameter hybrid pillar. A four-fold enhancement of quantum dot spontaneous emission rate is observed for quantum dots in resonance with excited degenerated modes of the pillar.
Physical Review B, 2009
The light emission rate of a single quantum dot can be drastically enhanced by embedding it in a resonant semiconductor microcavity. This phenomenon is known as the Purcell effect, and the coupling strength between emitter and cavity can be quantified by the Purcell factor. The most natural way for probing the Purcell effect is a time-resolved measurement. However, this approach is not always the most convenient one, and alternative approaches based on a continuouswave measurement are often more appropriate. Various signatures of the Purcell effect can indeed be observed using continuous-wave measurements (increase of the pump rate needed to saturate the quantum dot emission, enhancement of its emission rate at saturation, change of its radiation pattern), signatures which are encountered when a quantum dot is put on-resonance with the cavity mode. All these observations potentially allow one to estimate the Purcell factor. In this paper, we carry out these different types of measurements for a single quantum dot in a pillar microcavity and we compare their reliability. We include in the data analysis the presence of independent, nonresonant emitters in the microcavity environment, which are responsible for a part of the observed fluorescence.
Radiative emission dynamics of quantum dots in a single cavity micropillar
Physical Review B, 2006
The light emission of self-assembled (In,Ga)As/GaAs quantum dots embedded in single GaAsbased micropillars has been studied by time-resolved photoluminescence spectroscopy. The altered spontaneous emission is found to be accompanied by a non-exponential decay of the photoluminescence where the decay rate strongly depends on the excitation intensity. A microscopic theory of the quantum dot photon emission is used to explain both, the non-exponential decay and its intensity dependence. Also the transition from spontaneous to stimulated emission is studied.
Purcell effect of GaAs quantum dots by photonic crystal microcavities
Chinese Optics Letters, 2009
We fabricate photonic crystal slab microcavities embedded with GaAs quantum dots by electron beam lithography and droplet epitaxy. The Purcell effect of exciton emission of the quantum dots is confirmed by the micro photoluminescence measurement. The resonance wavelengths, widths, and polarization are consistent with numerical simulation results.
Emission characteristics of quantum dots in planar microcavities
Physical Review B, 2006
The emission properties of single quantum dots in planar microcavities are studied experimentally and theoretically. Fivefold Enhanced spontaneous emission outside the microcavity is found for dots in resonance with the cavity mode, relative to detuned dots, while their radiative lifetime is only marginally decreased. Using high power excitation we obtain the in-plane cavity dispersion. Near field images of the emission show spatial distributions of several microns for resonant dots, which decrease in size with the detuning from resonance. These experimental findings are explained using a simple and intuitive model.
Inhibition and Enhancement of the Spontaneous Emission of Quantum Dots in Structured Microresonators
Physical Review Letters, 2001
We present a micropillar cavity where nondesired radial emission is inhibited. The photonic confinement in such a structure is improved by implementation of an additional concentric radial-distributed Bragg reflector. Such a reflector increases the reflectivity in all directions perpendicular to the micropillar axis from a typical value of 15À31% to above 98%. An inhibition of the spontaneous emission of off-resonant excitonic states of quantum dots embedded in the microcavity is revealed by time-resolved experiments. It proves a decreased density of photonic states related to unwanted radial leakage of photons out of the micropillar. For on-resonance conditions, we find that the dot emission rate is increased, evidencing the Purcell enhancement of spontaneous emission. The proposed design can increase the efficiency of single-photon sources and bring to micropillar cavities the functionalities based on lengthened decay times. KEYWORDS: micropillar cavity . quantum dot . spontaneous emission inhibition . leaky mode . radial-distributed Bragg reflector . Purcell effect ARTICLE This is an open access article published under an ACS AuthorChoice License, which permits copying and redistribution of the article or any adaptations for non-commercial purposes. Downloaded by CNRS REGION RHONE ALPES on September 2, 2015 |
Enhanced coupling of electronic and photonic states in a microcavity-quantum dot system
Spherical microcavities consisting of a dielectric material show unique optical characteristics as resonators in combination with semiconductor nanoparticles. A high quality factor results in a very narrow bandwidth of the resonant modes (whispering-gallery modes) inside the microcavity. The polystyrene microspheres are coated with one monolayer of CdTe nanocrystals which offer a high photostability and a high quantum yield at room temperature. Due to strong confinement of the electrons in all three dimensions, excitation from the quantum dots is highly size-dependent and tuneable over almost the whole visible spectrum. The deposition of the nanocrystals on the sphere surface allows efficient coupling of the light of the CdTe quantum dots into the microcavity. Photoluminescence and Raman spectra were taken with a Renishaw Raman system. The setup is equipped with an Ar + -laser and a HeNe-laser to excite the nanocrystals. Raman measurements show a series of very sharp resonant peaks instead of a continuous spectrum. Strong interaction between the electronic states of the nanocrystals and the resonant modes in the microsphere causes a considerable enhancement of the Raman scattering and luminescence from the CdTe quantum dots in Stokes and anti-Stokes region. Furthermore, a linear blue shift of the resonances in the photoluminescence spectrum was observed during continuous excitation for 18 minutes with a HeNe laser.
Photoluminescence from site-selected coupling between quantum dots and microtoroid cavities
2010
By using CdSe/ZnS quantum dots (QDs), we study the effect of cavity quantum electrodynamics on the coupling of the microtoroid cavity. When with whispering gallery (WG) modes, the microtoroid cavity demonstrates high quality factor and small mode volume at visible wavelengths. Accordingly, fiber tapers allow QDs to adhere into the cavity and further permit the control of site-selected coupling. From the luminescence spectra, QDs are modulated effectively by cavity modes. Variable modulations are observed by changing QD coupling conditions. Therefore, based on experimental and theoretical research, strong and tunable Purcell enhancement can be realized by this system.