752 research outputs found
Buried heterostructure vertical-cavity surface-emitting laser with semiconductor mirrors
We report a buried heterostructure vertical-cavity surface-emitting laser
fabricated by epitaxial regrowth over an InGaAs quantum well gain medium. The
regrowth technique enables microscale lateral confinement that preserves a high
cavity quality factor (loaded 4000) and eliminates parasitic
charging effects found in existing approaches. Under optimal spectral overlap
between gain medium and cavity mode (achieved here at = 40 K) lasing was
obtained with an incident optical power as low as = 10 mW
( = 808 nm). The laser linewidth was found to be 3
GHz at 5
Quantum dot photonic crystal lasers
Coupled cavity designs on two-dimensional square lattice photonic crystal slabs were used to demonstrate optically pumped indium arsenide quantum dot photonic crystal lasers at room temperature. Threshold pump powers of 120 and 370 μW were observed for coupled cavities including two and four defect cavities defined in optimised photonic crystals
Critical Collapse in Einstein-Gauss-Bonnet Gravity in Five and Six Dimensions
Einstein-Gauss-Bonnet gravity (EGB) provides a natural higher dimensional and
higher order curvature generalization of Einstein gravity. It contains a new,
presumably microscopic, length scale that should affect short distance
properties of the dynamics, such as Choptuik scaling. We present the results of
a numerical analysis in generalized flat slice co-ordinates of self-gravitating
massless scalar spherical collapse in five and six dimensional EGB gravity near
the threshold of black hole formation. Remarkably, the behaviour is universal
(i.e. independent of initial data) but qualitatively different in five and six
dimensions. In five dimensions there is a minimum horizon radius, suggestive of
a first order transition between black hole and dispersive initial data. In six
dimensions no radius gap is evident. Instead, below the GB scale there is a
change in the critical exponent and echoing period.Comment: 21 pages, 39 figures, a couple of references and two new figures
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Semiconductor laser monolithically pumped with a light emitting diode operating in the thermoelectrophotonic regime
Data are presented on a monolithic chip that integrates a quantum well semiconductor laser with a high efficiency light emitting diode (LED), with the LED used to optically pump the laser. The LED operates in the thermoelectrophotonic regime that can produce heat absorption, offering the possibility of heat pump action. The internal optical pumping also offers the possibility of very low internal loss in the laser and the prospect of reaching greater than unity power conversion efficiency in the laser chip. The integrated laser chip is operated and tested under continuous-wave room temperature operation
Scanning a photonic crystal slab nanocavity by condensation of xenon
Allowing xenon or nitrogen gas to condense onto a photonic crystal slab nanocavity maintained at 10–20 K results in shifts of the nanocavity mode wavelength by as much as 5 nm (~=4 meV). This occurs in spite of the fact that the mode defect is achieved by omitting three holes to form the spacer. This technique should be useful in changing the detuning between a single quantum dot transition and the nanocavity mode for cavity quantum electrodynamics experiments, such as mapping out a strong coupling anticrossing curve. Compared with temperature scanning, it has a much larger scan range and avoids phonon broadening
High spontaneous emission coupling factor in photonic crystal nanolasers
We have demonstrated high spontaneous emission coupling factor ~ 0.1 from photonic crystal nanolasers with quantum dots. This high coupling resulted from narrow homogenous broadening of the quantum dots and the small number of resonances
Vacuum rabi splitting using a single quantum dot in a photonic crystal slab nanocavity
We report the observation of vacuum-field Rabi splitting (true strong coupling) between a single InAs quantum dot and a single photon in the mode of a photonic crystal slab nanocavity
Absence of correlation between built-in electric dipole moment and quantum Stark effect in InAs/GaAs self-assembled quantum dots
We report significant deviations from the usual quadratic dependence of the
ground state interband transition energy on applied electric fields in
InAs/GaAs self-assembled quantum dots. In particular, we show that conventional
second-order perturbation theory fails to correctly describe the Stark shift
for electric field below kV/cm in high dots. Eight-band calculations demonstrate this effect is predominantly due to
the three-dimensional strain field distribution which for various dot shapes
and stoichiometric compositions drastically affects the hole ground state. Our
conclusions are supported by two independent experiments.Comment: 4 pages, 4 figure
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