Quantum dot photonic-crystal-slab nanocavities: Quality factors and lasing (original) (raw)
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Optics Express, 2013
We present an experimental and theoretical study on the gain mechanism in a photonic-crystal-cavity nanolaser with embedded quantum dots. From time-resolved measurements at low excitation power we find that four excitons are coupled to the cavity. At high excitation power we observe a smooth low-threshold transition from spontaneous emission to lasing. Before lasing emission sets in, however, the excitons are observed to saturate, and the gain required for lasing originates rather from multiexcitonic transitions, which give rise to a broad emission background. We compare the experiment to a model of quantum-dot microcavity lasers and find that the number of excitons that must be included to fit the data largely exceeds the measured number, which shows that transitions involving the wetting layer can provide a surprisingly large contribution to the gain.
Nanobeam photonic crystal cavity quantum dot laser
Optics Express, 2010
The lasing behavior of one dimensional GaAs nanobeam cavities with embedded InAs quantum dots is studied at room temperature. Lasing is observed throughout the quantum dot PL spectrum, and the wavelength dependence of the threshold is calculated. We study the cavity lasers under both 780 nm and 980 nm pump, finding thresholds as low as 0.3 uW and 19 uW for the two pump wavelengths, respectively. Finally, the nanobeam cavity laser wavelengths are tuned by up to 7 nm by employing a fiber taper in near proximity to the cavities. The fiber taper is used both to efficiently pump the cavity and collect the cavity emission.
Self-Tuned Quantum Dot Gain in Photonic Crystal Lasers
Physical Review Letters, 2006
We demonstrate that very few (1 to 3) quantum dots as a gain medium are sufficient to realize a photonic crystal laser based on a high-quality nanocavity. Photon correlation measurements show a transition from a thermal to a coherent light state proving that lasing action occurs at ultra-low thresholds. Observation of lasing is unexpected since the cavity mode is in general not resonant with the discrete quantum dot states and emission at those frequencies is suppressed. In this situation, the quasi-continuous quantum dot states become crucial since they provide an energy-transfer channel into the lasing mode, effectively leading to a self-tuned resonance for the gain medium.
Photonic crystal nanocavities with quantum well or quantum dot active material
Photonic Crystal Materials and Devices II, 2004
We have investigated the miniaturization of photonic devices for ultimate photon localization, and have demonstrated two-dimensional photonic crystal nanolasers with two important quantum nanostructures-quantum wells (QWs) and quantum dots (QDs). Photonic crystal cavities with QW active material are simple, but powerful nanolasers to produce intense laser output for signal processing. On the other hand, when located in a highquality factor (Q) nanocavity, because QD(s) strongly couple with the intense optical field, QD photonic crystal cavities are expected to be good experimental setups to study cavity quantum electrodynamics, in addition to high speed and compact laser sources. Our photonic crystal nanolasers have showed as small thresholds as 0.12mW and 0.22mW for QD-photonic crystal lasers and QW-photonic crystal lasers, respectively, by proper cavity designs and nanofabrication. For QD-photonic crystal lasers, whispering gallery modes in square lattice were used together with coupled cavity designs and, for QW-photonic crystal lasers, quadrapole modes in triangular lattice with fractional edge dislocations were used to produce high-Q modes with small mode volume.
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.
Cavity QED with quantum dots in semiconductor microcavities
Quantum Dots, Particles, and Nanoclusters IV, 2007
Cavity quantum electrodynamic (QED) effects are studied in semiconductor microcavities embedded with InGaAs quantum dots. Evidence of weak coupling in the form of lifetime enhancement (the Purcell effect) and inhibition is found in both oxide-apertured micropillars and photonic crystals. In addition, high-efficiency, low-threshold lasing is observed in the photonic crystal cavities where only 2-4 quantum dots exist within the cavity mode volume and are not in general spectrally resonant. The transition to lasing in these soft turn-on devices is explored in a series of nanocavities by observing the change in photon statistics of the cavity mode with increasing pump power near the threshold.
Applied Physics Letters, 2001
We have characterized the modes within two-dimensional photonic crystal nanocavities with self-organized indium arsenide quantum dots as an active material. Highly localized donor mode resonances with 3 to 5 nm linewidth were observed when spatially selective optical pumping the cavities. These modes could be lithographically tuned from 1100 to 1300 nm. Other, more extended modes, were also characterized and exhibited narrower resonance linewidths ranging from 0.6 to 2 nm.
Quantum dot nano-cavity emission tuned by a circular photonic crystal lattice
Microelectronic Engineering, 2007
In this work the analysis, fabrication and optical characterization of a circular two-dimensional photonic crystal (2D-CPC) nano-resonator based on a air/GaAs/air slab waveguide are presented. Four InAs/InGaAs quantum dots (QDs) stacked layers emitting around 1300 nm were embedded in a GaAs waveguide layer grown on an Al 0.7 Ga 0.3 As sacrificial layer. The nano-resonator was realized by drilling 2D-PC air holes arranged in a circular lattice configuration through electron beam lithography (EBL), inductively coupled plasma (ICP) etching and wet selective etching of the Al 0.7 Ga 0.3 As sacrificial layer in order to release the membrane. The spectral response of the active circular nano-cavity has been simulated by using a three dimensional finite-difference time-domain method (3D-FDTD) as a function of both the inner and outer holes radius/period ratios of the photonic crystal structure. Good agreement between the calculated resonance and the experimental results, recorded from the nano-cavity by a lPL setup, has been achieved.