A5016479949- Spectroscopy and Laser Applications
- Terahertz technology and applications
- Photonic and Optical Devices
- Semiconductor Quantum Structures and Devices
- Laser-induced spectroscopy and plasma
- Silicon Nanostructures and Photoluminescence
- Planetary Science and Exploration
- Atmospheric Ozone and Climate
- Astro and Planetary Science
- Silicon and Solar Cell Technologies
- Laser Design and Applications
- Quantum and electron transport phenomena
- Isotope Analysis in Ecology
- Advanced Semiconductor Detectors and Materials
- Advanced Fiber Laser Technologies
- Semiconductor materials and interfaces
- Mechanical and Optical Resonators
- Semiconductor Lasers and Optical Devices
- Analytical chemistry methods development
- Semiconductor materials and devices
- Superconducting and THz Device Technology
- Photocathodes and Microchannel Plates
- Laser-Matter Interactions and Applications
- Electron and X-Ray Spectroscopy Techniques
- Advancements in Semiconductor Devices and Circuit Design
Deutsches Zentrum für Luft- und Raumfahrt e. V. (DLR)
2015-2024
University of Central Florida
2020
Institute for Physics of Microstructures
2008-2020
Radboud University Nijmegen
2020
Delft University of Technology
2020
University of Leeds
2020
Humboldt-Universität zu Berlin
2016-2019
Planet
2008-2013
Planetary Science Institute
2013
Institute for Atomic and Molecular Physics
2008
The quantum cascade laser is a powerful, narrow linewidth, and continuous wave source of terahertz radiation. authors have implemented distributed feedback device in spectrometer for high-resolution gas phase spectroscopy. Amplitude as well frequency modulation schemes been realized. absolute was determined by mixing the radiation from with that laser. pressure broadening shift rotational transition methanol at 2.519THz were measured order to demonstrate performance spectrometer.
Terahertz quantum cascade lasers have been investigated with respect to their performance as a local oscillator in heterodyne receiver. The beam profile has measured and transformed close Gaussian resulting good matching between the field patterns of laser antenna superconducting hot electron bolometric mixer. Noise temperature measurements bolometer 2.5 THz yielded same result gas oscillator.
Recent experimental and theoretical results of impurity doped germanium silicon terahertz lasers are reviewed. Three different laser mechanisms exist in p-type germanium. Depending on the operating conditions properties crystal, transitions can occur between light- heavy-hole subbands, particular light-hole Landau levels or states. Electric magnetic fields required for operation. In n-type lasing originates solely from group-V donors, which optically excited. The these depend upon chemical...
A liquid cryogen-free terahertz heterodyne receiver in a pulse tube cooler has been realized. The operates at 2.5 THz. It is based on quantum cascade laser (QCL) as local oscillator and hot electron bolometric mixer. detailed study of the QCL beam quality yielded propagation factor 1.1–1.2. double sideband noise temperature system 2000 K when corrected for optical losses signal path it ∼800 K.
We report on the development of a compact, easy-to-use terahertz radiation source, which combines quantum-cascade laser (QCL) operating at 3.1 THz with low-input-power Stirling cooler. The QCL, is based two-miniband design, has been developed for high output and low electrical pump power. amount generated heat complies nominal cooling capacity cooler 7 W 65 K 240 input Special care taken to achieve good thermal coupling between QCL cold finger whole system weighs less than 15 kg including...
Laboratory spectroscopy of atomic hydrogen in a magnetic flux density 105 T (1 gigagauss), the maximum observed on high-field white dwarfs, is impossible because practically available fields are about thousand times less. In this regime, cyclotron and binding energies become equal. Here we demonstrate Lyman series spectra for phosphorus impurities silicon up to equivalent field, which scaled 32.8 by effective mass dielectric constant. The reproduce theory free hydrogen, with quadratic Zeeman...
Stimulated Stokes emission has been observed from silicon crystals doped by antimony donors when optically excited radiation a tunable infrared free electron laser. The photon energy of the is equal to pump reduced intervalley transverse acoustic (TA) $g$ phonon in ($\ensuremath{\approx}2.92\text{ }\text{ }\mathrm{THz}$). frequency covers range 4.6--5.8 THz. laser process occurs due resonant coupling $1s(E)$ and $1s({A}_{1})$ donor states (separation $\ensuremath{\approx}2.97\text{...
Abstract The first silicon laser was reported in the year 2000. It is based on impurity transitions of hydrogen‐like phosphorus donor monocrystalline silicon. Several lasers other group‐V donors have been demonstrated since then. These operate at low lattice temperatures under optical pumping by a midinfrared and emit light discrete wavelengths range from 50 to 230 µm (between 1.2 6.9 THz). Dipole‐allowed between particular excited states substitutional are utilized for donor‐type terahertz...
We investigate ultrafast harmonic generation (HG) in Si:B, driven by intense pump pulses with fields reaching $\ensuremath{\sim}100\phantom{\rule{0.28em}{0ex}}\mathrm{kV}\phantom{\rule{0.16em}{0ex}}{\mathrm{cm}}^{\ensuremath{-}1}$ and a carrier frequency of 300 GHz, at 4 K K, both experimentally theoretically. report several findings concerning the nonlinear charge dynamics sub-THz fields: (i) Harmonics order up to $n=9$ are observed room temperature, while low temperature we can resolve...
Frequency-tunable radiation from the free electron laser FELIX was used to excite neutral phosphorus and bismuth donors embedded in bulk monocrystalline silicon. Lasing at terahertz frequencies has been observed liquid helium temperature while resonant pumping of odd parity impurity states. The threshold about two orders magnitude below value for photoionization pumping. influence nonequilibrium intervalley TO phonons on population excited Bi states is discussed.
Upcoming lander missions to planetary bodies require new innovative techniques for the in situ investigation of their surfaces and near‐surface materials. In recent years, Raman spectroscopy has been developed become an excellent laboratory tool fast petrological mineralogical terrestrial extraterrestrial rocks. Consequently, successfully proposed operation on surfaces. For example, Laser Spectrometer joint European Space Agency Roscosmos mission ExoMars will, first time space, identify...
Stimulated emission has been obtained from intra-center donor transitions in silicon monocrystals doped by arsenic. The Si:As laser was optically excited radiation a CO2 laser. spectrum consists of two lines corresponding to the 2p±→1s(E) and 2p±→1s(T2) arcenic transitions. population inversion is formed due fast 2s→1s(A1) electron relaxation assisted intervalley longitudinal acoustic f-phonon emission. This keeps states below 2p± state unpopulated. Thus occurs between 1s(E), 1s(T2) states.
We report on a terahertz absorption spectrometer, which combines grating monochromator, quantum-cascade laser (QCL), and microbolometer camera. The emission modes of the are spectrally resolved by monochromator imaged onto An cell is placed between QCL spectrum methanol around 3.4 THz measured integrating simultaneously signal each its Fabry-Pérot as function driving current. frequency coverage spectrometer about 20 GHz.
The low-temperature (\ensuremath{\sim}5 K) phonon-assisted relaxation of the 2${p}_{0}$ state phosphorus donors in isotopically pure, monocrystalline ${}^{28}$Si has been studied time domain using a pump-probe technique. lifetime ${}^{28}$Si:P is found to be 235 ps, which 16$%$ larger than reference Si:P sample with natural isotope composition. interaction intervalley $g$-type longitudinal acoustic and $f$-type transverse phonons determines its lifetime. This interaction, depends on...
The low temperature ($T$ = 5--40 K) capture of free electrons into hydrogenlike antimony centers in germanium has been studied by a time-resolving experiment using the electron laser FELBE. analysis pump-probe signal reveals typical time about 1.7 ns that decreases with pump energy to less than 1 while number ionized donors increases. dependence on pump-pulse is well described an acoustic phonon-assisted process. In cases when (i) significant conduction band (flux densities larger 5...
Interband photoluminescence (PL) and stimulation emission (SE) from HgTe/HgCdTe quantum well (QW) heterostructures are studied in 5–20 µm wavelength range regard to long‐wavelength lasing applications. The authors obtain carrier lifetimes using time‐resolved photoconductivity measurements show that the dominating mechanism of recombination changes radiative process non‐radiative one as bandgap is decreased, limiting “operating” temperature for SE. suggest decreasing QW width should reverse...
The origins of line broadening in the far-infrared spectrum phosphorus donors SiGe are investigated. Using a combination Fourier transform infrared (FT-IR) spectroscopy and time-resolved pump-probe measurements, we show that shapes dominated by inhomogenous broadening. Experimental FT-IR absorbance spectra measured temperature range 6--150 K presented for three different Ge contents. Additional pure doped silicon recorded under similar experimental conditions compared with results. We...
Doping of silicon with magnesium is investigated by a sandwich diffusion technique. Temperature dependence the coefficient in dislocation‐free range 1000–1200 °C determined. It obeys Arrhenius behavior over 600–1200 °C, when data obtained earlier for lower temperatures are taken into consideration. Preliminary results on Mg dislocated crystals also presented. The Si:Mg samples Hall‐effect measurements and low‐temperature Fourier spectroscopy. A decrease concentration interstitials (about...