64 research outputs found
Optical and electronic properties of low-density InAs/InP quantum dot-like structures devoted to single-photon emitters at telecom wavelengths
Due to their band-structure and optical properties, InAs/InP quantum dots
(QDs) constitute a promising system for single-photon generation at third
telecom window of silica fibers and for applications in quantum communication
networks. However, obtaining the necessary low in-plane density of emitters
remains a challenge. Such structures are also still less explored than their
InAs/GaAs counterparts regarding optical properties of confined carriers. Here,
we report on the growth via metal-organic vapor phase epitaxy and investigation
of low-density InAs/InP QD-like structures, emitting in the range of 1.2-1.7
m, which includes the S, C, and L bands of the third optical window. We
observe multiple photoluminescence (PL) peaks originating from flat QDs with
height of small integer numbers of material monolayers. Temperature-dependent
PL reveals redistribution of carriers between families of QDs. Via
time-resolved PL, we obtain radiative lifetimes nearly independent of emission
energy in contrast to previous reports on InAs/InP QDs, which we attribute to
strongly height-dependent electron-hole correlations. Additionally, we observe
neutral and charged exciton emission from spatially isolated emitters. Using
the 8-band kp model and configuration-interaction method, we
successfully reproduce energies of emission lines, the dispersion of exciton
lifetimes, carrier activation energies, as well as the biexciton binding
energy, which allows for a detailed and comprehensive analysis of the
underlying physics.Comment: 13 pages, 9 figure
Spin coherence of holes in GaAs/AlGaAs quantum wells
The carrier spin coherence in a p-doped GaAs/(Al,Ga)As quantum well with a
diluted hole gas has been studied by picosecond pump-probe Kerr rotation with
an in-plane magnetic field. For resonant optical excitation of the positively
charged exciton the spin precession shows two types of oscillations. Fast
oscillating electron spin beats decay with the radiative lifetime of the
charged exciton of 50 ps. Long lived spin coherence of the holes with dephasing
times up to 650 ps. The spin dephasing time as well as the in-plane hole g
factor show strong temperature dependence, underlining the importance of hole
localization at cryogenic temperatures.Comment: 5 pages, 4 figures in PostScript forma
Exciton lifetime and emission polarization dispersion in strongly in-plane asymmetric nanostructures
We present experimental and theoretical investigation of exciton
recombination dynamics and the related polarization of emission in highly
in-plane asymmetric nanostructures. Considering general asymmetry- and
size-driven effects, we illustrate them with a detailed analysis of
InAs/AlGaInAs/InP elongated quantum dots. These offer a widely varied
confinement characteristics tuned by size and geometry that are tailored during
the growth process, which leads to emission in the application-relevant
spectral range of 1.25-1.65 {\mu}m. By exploring the interplay of the very
shallow hole confining potential and widely varying structural asymmetry, we
show that a transition from the strong through intermediate to even weak
confinement regime is possible in nanostructures of this kind. This has a
significant impact on exciton recombination dynamics and the polarization of
emission, which are shown to depend not only on details of the calculated
excitonic states but also on excitation conditions in the photoluminescence
experiments. We estimate the impact of the latter and propose a way to
determine the intrinsic polarization-dependent exciton light-matter coupling
based on kinetic characteristics.Comment: 11 pages, 8 figure
Observation of gain-pinned dissipative solitons in a microcavity laser
This work was supported by the National Science Center in Poland, by Grant Nos. 2016/23/N/ST3/01350 and 2018/30/E/ST7/00648, and by the Polish National Agency for Academic Exchange. The Würzburg group gratefully acknowledges support by the State of Bavaria. The work at the Australian National University was supported by the Australian Research Council.We demonstrate an experimental approach for creating spatially localized states in a semiconductor microcavity laser. In particular, we shape the spatial gain profile of a quasi-one-dimensional microcavity laser with a nonresonant, pulsed optical pump to create spatially localized structures, known as gain-pinned dissipative solitons, that exist due to the balance of gain and nonlinear losses. We directly probe the ultrafast formation dynamics and decay of these localized structures, showing that they are created on a picosecond timescale, orders of magnitude faster than laser cavity solitons. All of the experimentally observed features and dynamics are reconstructed by numerical modeling using a complex Ginzburg-Landau model, which explicitly takes into account the carrier density dynamics in the semiconductor.Publisher PDFPeer reviewe
Room temperature carrier kinetics in the W-type GaInAsSb/InAs/AlSb quantum well structure emitting in mid-infrared spectral range
Room temperature carrier kinetics has been investigated in the type-II W-design AlSb/InAs/Ga0:80In0:20As0:15Sb0:85/InAs/AlSb quantum well emitting in the mid-infrared spectral range (at 2.54 μm). A timeresolved reflectance technique, employing the non-degenerated pump-probe scheme, has been used as a main experimental tool. Based on that, a primary carrier relaxation time of 2:3 ± 0:2 ps has been found, and attributed to the initial carrier cooling process within the quantum well states, while going towards the ground state via the carrier-optical phonon scattering mechanism. The decay of a quasi-equilibrium carrier population at the quantum well ground states is primarily governed by two relaxation channels: (i) radiative recombination within distribution of spatially separated electrons and holes that occurs in the nanosecond time scale, and (ii) the hole tunnelling out of its confining potential, characterized by a 240 ± 10 ps time constant.Publisher PD
Single-photon emission of InAs/InP quantum dashes at 1.55 μm and temperatures up to 80 K
This research was supported by the National Science Center of Poland within Grant No. 2011/02/A/ST3/00152.We report on single photon emission from a self-assembled InAs/InGaAlAs/InP quantum dash emitting at 1.55 µm at elevated temperatures. The photon auto-correlation histograms of the emission from a charged exciton indicate clear antibunching dips with as-measured g(2)(0) values significantly below 0.5 recorded at temperatures up to 80 K. It proves that charged exciton complex in a single quantum dash of the mature InP-based material system can act as a true single photon source up to at least liquid nitrogen temperature. This demonstrates the huge potential of InAs on InP nanostructures as non-classical light emitters for long-distance fiber-based secure communication technologies.PostprintPublisher PDFPeer reviewe
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