A5079934185- Semiconductor Quantum Structures and Devices
- Quantum and electron transport phenomena
- Strong Light-Matter Interactions
- Silicon Nanostructures and Photoluminescence
- Magnetic properties of thin films
- Terahertz technology and applications
- Nanowire Synthesis and Applications
- Physics of Superconductivity and Magnetism
- Magneto-Optical Properties and Applications
- Photonic and Optical Devices
- Plasmonic and Surface Plasmon Research
- Photonic Crystals and Applications
- Mechanical and Optical Resonators
- Thermal Radiation and Cooling Technologies
- Thin-Film Transistor Technologies
- Cold Atom Physics and Bose-Einstein Condensates
- Spectroscopy and Quantum Chemical Studies
- Laser-Matter Interactions and Applications
- Orbital Angular Momentum in Optics
- Semiconductor materials and interfaces
- Advanced Semiconductor Detectors and Materials
- Spectroscopy and Laser Applications
- Molecular Junctions and Nanostructures
- Quantum Dots Synthesis And Properties
- Quantum Information and Cryptography
Charles University
2015-2024
Czech Academy of Sciences, Institute of Physics
2019
Czech Academy of Sciences
2019
University of Southampton
2009-2011
University of California, Santa Barbara
2009
Institut de Physique et Chimie des Matériaux de Strasbourg
2004-2007
Centre National de la Recherche Scientifique
2004-2007
University of Trento
2004
Quantum Division The notion of quantum mechanics is that variables are expressed as integer values. In fluids, for instance, vortices quantized in terms the polarization and phase shifts observed multiples 2π, is, full rotations each variable around vortex core. Theoretical work has predicted some instances there should be half-quantum vortices, where circumventing core characterized by just π polarization. By observing exciton-polariton condensates Lagoudakis et al. (p. 974 ) present...
We show that logical signals encoded in bistable states semiconductor microcavities can be generated and controlled electronically by exploiting the electrical sensitivity of Tamm-plasmon--exciton-polariton modes. The transported along polariton neurons, created with a patterned metal surface. Using Gross-Pitaevskii equations, we simulate an electrically transistor find high repetition rates (10 GHz) are possible.
We report on the observation of a spin texture in cold exciton gas GaAs/AlGaAs coupled quantum well structure. The is observed around rings. phenomena include: ring linear polarization, vortex polarization with perpendicular to radial direction, an anisotropy flux, skew fluxes orthogonal circular polarizations and corresponding four-leaf pattern periodic texture, extended coherence region vortex. data indicate transport regime where locked direction particle propagation scattering suppressed.
We investigate the propagation and scattering of polaritons in a planar GaAs microcavity linear regime under resonant excitation. The coherent polariton wave across an extended defect creates phase intensity patterns with identical qualitative features previously attributed to dark half-dark solitons polaritons. demonstrate that these are observed for negligible nonlinearity (i.e., polariton-polariton interaction) are, therefore, not sufficient identify solitons. A model based on Maxwell...
Abstract We present a method for precise determination of magnetic anisotropy and quadratic magneto-optical (MO) response thin films ferromagnetic ferrimagnetic materials. The is based on measurements MO light close to the normal incidence sample with fixed position. measurement performed set orientations an external field series incident linear polarizations beyond standard s p orientations. Based symmetry signal, we are able separate part that even respect magnetization and, in turn,...
We demonstrate the role of longitudinal optical (LO)-phonon assisted polariton relaxation in reducing stimulation threshold strongly coupled microcavities. When energy bottleneck is one LO-phonon above ground state, we observe a tenfold improvement rate linear regime, and twofold reduction to nonlinear lasing regime.
Antiferromagnets offer spintronic device characteristics unparalleled in ferromagnets owing to their lack of stray fields, THz spin dynamics, and rich materials landscape. Microscopic imaging antiferromagnetic domains is one the key prerequisites for understanding physical principles operation. However, adapting common magnetometry techniques dipolar-field-free antiferromagnets has been a major challenge. Here we demonstrate collinear antiferromagnet thermoelectric detection method by...
Spin transport of indirect excitons in GaAs/AlGaAs coupled quantum wells was observed by measuring the spatially resolved circular polarization exciton emission. The spin originates from long relaxation time and lifetime excitons.
We observe anisotropy in the polarization flux generated a GaAs/AlAs photonic cavity by optical illumination, equivalent to spin currents strongly coupled microcavities. Polarization rotation of scattered photons around Rayleigh ring is due TE-TM splitting mode. Resolving circular components transmission reveals separation momentum space. These observations constitute analogue Hall effect.
Magnetic linear dichroism and birefringence in (Ga,Mn)As epitaxial layers is investigated by measuring the polarization plane rotation of reflected linearly polarized light when magnetization lies sample. We report on spectral dependence ellipticity angles a broad energy range $0.12--2.7\phantom{\rule{4pt}{0ex}}\mathrm{eV}$ for series optimized samples covering wide Mn dopings Curie temperatures find clear blueshift dominant peak at exceeding host material band gap. These results are...
Silicon nanocrystals (Si-ncs) of sufficiently small size, emitting luminescence at short wavelengths (which implies the occurrence quasi-direct radiative recombination) and being densely packed in a planar thin film ensures stimulated emission (StE) lifetime) can become suitable active material for observation StE visible region. In this paper, we describe fabrication method nanostructures type, based on enhanced electrochemical etching silicon wafers followed by embedding porous grains into...
Efficient and controlled charge carrier transport through nanoelements is currently a primordial question in the research of nanoelectronic materials structures. We develop quantum-mechanical theory conductivity spectra confined carriers responding to an electric field from dc regime up optical frequencies. The broken translation symmetry induces broadband drift-diffusion current, which not taken into account analysis based on Kubo formula relaxation time approximation. show that this...
The propagation of light emitted from silicon nanocrystals forming planar waveguides buried in SiO2 is studied both experimentally and theoretically. Experiments reveal that photoluminescence spectra detected the sample facet mainly contains narrow (10–20nm full-with-at-half-maximum) polarization-resolved transverse electric magnetic modes instead usual broad nanocrystal emission band peaked at 700–800nm. A theoretical model developed framework wave optics identifies these as substrate...
Abstract Arrays of ultimate‐quality single‐crystalline GaAs nanobars are prepared via electron‐beam lithography in a molecular‐beam‐epitaxy‐grown layer transferred onto an electrically insulating and optically terahertz transparent sapphire substrate. Measurements ultrafast photoconductivity at 300 20 K array such aligned by time‐resolved multiterahertz spectroscopy scanning near‐field microscopy allow in‐depth understanding the nanoscale electron motion inside nanobars. A detailed analysis...
Time-resolved terahertz spectroscopy is used to investigate formation and ultrafast long-distance propagation of electron-hole plasma in strongly photoexcited GaAs InP. The observed phenomena involve fundamental interactions system with light, which manifest themselves two different regimes: a coherent one the speeds up c/10 (in at 20 K) an incoherent reaching c/25 InP K), both over macroscopic distance > 100 micrometers. We explore broad range experimental conditions by investigating...
We study the relaxation dynamics of spin-polarized exciton-polaritons using a technique in pump-probe configuration: According to their total angular momentum, can be excited by circularly polarized light either σ+ or σ− helicities. In addition, bound state two excitons may exist which transition is only allowed when photons opposite After excitation pump pulse helicity, additional polaritons from probe helicity absorbed excite biexcitons, while absorption those with becomes possible after...
We report on an experimental investigation of electron-, hole-, and exciton-spin relaxation times in intrinsic GaAs quantum wells. present non-degenerate pump-and-probe measurements followed by a detailed analysis the differential transmission spectra order to identify different spin channels. Dynamics is generally considered be multiexponential therefore dynamical model taking into account four exciton states used determine various times. In contrast other work, we also consider transitions...
Elastic scattering of exciton polaritons in planar semiconductor microcavities has been used to create X-NOR logic gates. Polaritons with identical linear polarization scatter preferentially at the right angle and rotate their by $90\ifmmode^\circ\else\textdegree\fi{}$. On other hand, having orthogonal polarizations is suppressed. We show that these effects are a consequence multiple which involve three more polaritons. The theory quantitatively reproduces experimental data C. Leyder et al....
We present an effective way to improve the security of a point-to-point terahertz wireless link on physical layer supported by numerical calculations in frame Fourier optics. The improvement is based original countermeasures which exploit three independent degrees freedom carrier wave: its intensity and azimuthal radial symmetry. When transmission line intercepted, light beam subject changes either freedom. propose strategy measure these they are quantified single eavesdropping parameter...
Electron-hole plasma expansion with velocities exceeding $c/50$ and lasting over 10 ps at 300 K was evidenced by time-resolved terahertz spectroscopy. This regime, in which the carriers are driven $>30\text{ }\text{ }\mathrm{\ensuremath{\mu}}\mathrm{m}$ is governed stimulated emission due to low-energy electron-hole pair recombination reabsorption of emitted photons outside volume. At low temperatures a speed $c/10$ observed regime where excitation pulse spectrally overlaps photons, leading...
Abstract Antiferromagnetic CuMnAs thin films have attracted attention since the discovery of manipulation their magnetic structure via electrical, optical, and terahertz pulses, enabling convenient approaches for switching between magnetoresistive states film information storage. However, and, thus, efficiency can be affected by morphology growth defects. In this study, properties are investigated probing asymmetrical growth‐related uniaxial anisotropy electric conductivity contact‐free...
We consider theoretically the elastic scattering of two exciton polaritons having opposite wave vectors in a planar microcavity. derive amplitudes accounting for vector polarization and interference different channels. obtain nontrivial dependence polarizations on angle initial states. Generation polariton spin currents as result linearly polarized is predicted. also describe depolarization due to their show that it may be complete certain directions. This analysis provides basis engineering...
Quantum-size effects are essential for understanding the terahertz conductivity of semiconductor nanocrystals, particularly at low temperatures. We derived a quantum mechanical expression linear response nanocrystals; its introduction into an appropriate effective medium model provides comprehensive microscopic approach analysis spectra as function frequency, temperature, and excitation fluence. performed optical pump--terahertz probe experiments in multilayer Si dot networks with various...