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Search Results: 1 - 10 of 2143 matches for " Mattias Beck "
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InGaAs/AlInGaAs THz Quantum Cascade Lasers operating up to 195 K in strong magnetic field
Federico Valmorra,Giacomo Scalari,Keita Ohtani,Mattias Beck,Jerome Faist
Physics , 2014, DOI: 10.1088/1367-2630/17/2/023050
Abstract: Terahertz quantum cascade lasers based on InGaAs wells and quaternary AlInGaAs barriers were measured in magnetic field. This study was carried out on a four quantum well active region design with photon energy of 14.3 meV processed both with Au and Cu waveguides. The heterostructure operates up to 148 K at B=0 T and in a Cu waveguide. The complete magneto-spectroscopic study allowed the comparison of emission and transport data. Increasing the magnetic field, the low effective mass of the InGaAs wells allowed us to reach the very strong confinement regime. At B=12 T, where the cyclotron transition is almost resonant with the LO-phonon, we recorded a maximum operating temperature of 195 K for the devices with Cu waveguide. Additional lasing at 5.9 meV was detected for magnetic fields between 7.3 and 7.7 T.
Osmostress-Induced Cell Volume Loss Delays Yeast Hog1 Signaling by Limiting Diffusion Processes and by Hog1-Specific Effects
Roja Babazadeh, Caroline Beck Adiels, Maria Smedh, Elzbieta Petelenz-Kurdziel, Mattias Goks?r, Stefan Hohmann
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0080901
Abstract: Signal transmission progresses via a series of transient protein-protein interactions and protein movements, which require diffusion within a cell packed with different molecules. Yeast Hog1, the effector protein kinase of the High Osmolarity Glycerol pathway, translocates transiently from the cytosol to the nucleus during adaptation to high external osmolarity. We followed the dynamics of osmostress-induced cell volume loss and Hog1 nuclear accumulation upon exposure of cells to different NaCl concentrations. While Hog1 nuclear accumulation peaked within five minutes following mild osmotic shock it was delayed up to six-fold under severe stress. The timing of Hog1 nuclear accumulation correlated with the degree of cell volume loss and the cells capacity to recover. Also the nuclear translocation of Msn2, the transcription factor of the general stress response pathway, is delayed upon severe osmotic stress suggesting a general phenomenon. We show by direct measurements that the general diffusion rate of Hog1 in the cytoplasm as well as its rate of nuclear transport are dramatically reduced following severe volume reduction. However, neither Hog1 phosphorylation nor Msn2 nuclear translocation were as much delayed as Hog1 nuclear translocation. Our data provide direct evidence that signaling slows down during cell volume compression, probably as a consequence of molecular crowding. Hence one purpose of osmotic adaptation is to restore optimal diffusion rates for biochemical and cell biological processes. In addition, there may be mechanisms slowing down especially Hog1 nuclear translocation under severe stress in order to prioritize Hog1 cytosolic targets.
Hydrodynamic Cell Trapping for High Throughput Single-Cell Applications
Amin Abbaszadeh Banaeiyan,Doryaneh Ahmadpour,Caroline Beck Adiels,Mattias Goks?r
Micromachines , 2013, DOI: 10.3390/mi4040414
Abstract: The possibility to conduct complete cell assays under a precisely controlled environment while consuming minor amounts of chemicals and precious drugs have made microfluidics an interesting candidate for quantitative single-cell studies. Here, we present an application-specific microfluidic device, cellcomb, capable of conducting high-throughput single-cell experiments. The system employs pure hydrodynamic forces for easy cell trapping and is readily fabricated in polydimethylsiloxane (PDMS) using soft lithography techniques. The cell-trapping array consists of V-shaped pockets designed to accommodate up to six Saccharomyces cerevisiae (yeast cells) with the average diameter of 4 μm. We used this platform to monitor the impact of flow rate modulation on the arsenite (As(III)) uptake in yeast. Redistribution of a green fluorescent protein (GFP)-tagged version of the heat shock protein Hsp104 was followed over time as read out. Results showed a clear reverse correlation between the arsenite uptake and three different adjusted low = 25 nL min ?1, moderate = 50 nL min ?1, and high = 100 nL min ?1 flow rates. We consider the presented device as the first building block of a future integrated application-specific cell-trapping array that can be used to conduct complete single cell experiments on different cell types.
Ultra strong coupling regime and plasmon-polaritons in parabolic semiconductor quantum wells
Markus Geiser,Fabrizio Castellano,Giacomo Scalari,Mattias Beck,Laurent Nevou,Jér?me Faist
Physics , 2011, DOI: 10.1103/PhysRevLett.108.106402
Abstract: Ultra strong coupling is studied in a modulation-doped parabolic potential well coupled to an inductance-capacitance resonant circuit. In this system, in accordance to Kohn's theorem, strong reduction of the energy level separation caused by the electron-electron interaction compensates the depolarization shift. As a result, a very large ratio of 27% of the Rabi frequency to the center resonance frequency as well as a polariton gap of width 2? ? 670GHz are observed, suggesting parabolic quantum wells as the system of choice in order to explore the ultra-strong coupling regime.
Sub-cycle measurement of intensity correlations in the Terahertz range
Ileana-Cristina Benea-Chelmus,Curdin Maissen,Giacomo Scalari,Mattias Beck,Jér?me Faist
Physics , 2015,
Abstract: The Terahertz frequency range bears intriguing opportunities, beyond very advanced applications in spectroscopy and matter control. Peculiar quantum phenomena are predicted to lead to light emission by non-trivial mechanisms. Typically, such emission mechanisms are unraveled by temporal correlation measurements of photon arrival times, as demonstrated in their pioneering work by Hanbury Brown and Twiss. So far, the Terahertz range misses an experimental implementation of such technique with very good temporal properties and high sensitivity. In this paper, we propose a room-temperature scheme to measure photon correlations at THz frequencies based on electro-optic sampling. The temporal resolution of 146 fs is faster than one cycle of oscillation and the sensitivity is so far limited to ~1500 photons. With this technique, we measure the photon statistics of a THz quantum cascade laser. The proposed measurement scheme allows, in principle, the measurement of ultrahigh bandwidth photons and paves the way towards THz quantum optics.
Octave-spanning semiconductor laser
Markus R?sch,Giacomo Scalari,Mattias Beck,Jér?me Faist
Physics , 2014, DOI: 10.1038/nphoton.2014.279
Abstract: We present here a semiconductor injection laser operating in continuous wave with an emission covering more than one octave in frequency, and displaying homogeneous power distribution among the lasing modes. The gain medium is based on a heterogeneous quantum cascade structure operating in the THz range. Laser emission in continuous wave takes place from 1.64 THz to 3.35 THz with optical powers in the mW range and more than 80 modes above threshold. Free-running beatnote investigations on narrow waveguides with linewidths of 980 Hz limited by jitter indicate frequency comb operation on a spectral bandwidth as wide as 624 GHz, making such devices ideal candidates for octave-spanning semiconductor-laser-based THz frequency combs.
Room temperature terahertz polariton emitter
Markus Geiser,Giacomo Scalari,Fabrizio Castellano,Mattias Beck,Jér?me Faist
Physics , 2012, DOI: 10.1063/1.4757611
Abstract: The strong-coupling regime between an electronic transition and the photonic mode of a optical resonator manifests itself in the lifting of the degeneracy between the two modes and the creation of two polariton states with mixed optical and electronic character. This phenomenon has been studied in atoms, excitons in semiconductors and quantum electrodynamics circuits based on Josephson junctions. Recently, there is also strong interest to study similar e?ects using intersubband transitions in quantum wells in the terahertz, where the ultra strong coupling regime can be reached and new physical e?ects have been predicted. An other interesting feature of this system is that, in contrast to systems based on superconductors, the ultra strong coupling regime can be maintained up to room temperature. In this work, we demonstrate that parabolic quantum wells coupled to LC circuit resonators in the ultra strong coupling regime can achieve terahertz emission up to room temperature.
Observation of Zone-Folded Acoustic Phonons in Terahertz Quantum Cascade Lasers using Picosecond Ultrasonics
Axel Bruchhausen,Mike Hettich,James Lloyd-Hughes,Milan Fischer,Mattias Beck,Giacomo Scalari,Jér?me Faist,Thomas Dekorsy
Physics , 2010,
Abstract: We have investigated the time-resolved vibrational properties of terahertz quantum cascade lasers by means of ultra-fast laser spectroscopy. By the observation of the acoustic folded branches, and by analyzing the involved phonon modes it is possible to extract accurate structural information of these devices, which are essential for their design and performance.
Dispersion engineering of Quantum Cascade Lasers frequency combs
Gustavo Villares,Sabine Riedi,Johanna Wolf,Dmitry Kazakov,Martin J. Süess,Mattias Beck,Jér?me Faist
Physics , 2015,
Abstract: Quantum cascade lasers are compact sources capable of generating frequency combs. Yet key characteristics - such as optical bandwidth and power-per-mode distribution - have to be improved for better addressing spectroscopy applications. Group delay dispersion plays an important role in the comb formation. In this work, we demonstrate that a dispersion compensation scheme based on a Gires-Tournois Interferometer integrated into the QCL-comb dramatically improves the comb operation regime, preventing the formation of high-phase noise regimes previously observed. The continuous-wave output power of these combs is typically $>$ 100 mW with optical spectra centered at 1330 cm$^{-1}$ (7.52 $\mu$m) with $\sim$ 70 cm$^{-1}$ of optical bandwidth. Our findings demonstrate that QCL-combs are ideal sources for chip-based frequency comb spectroscopy systems.
On-chip Dual-comb based on Quantum Cascade Laser Frequency Combs
Gustavo Villares,Johanna Wolf,Dmitry Kazakov,Martin J Süess,Andreas Hugi,Mattias Beck,Jér?me Faist
Physics , 2015,
Abstract: Dual-comb spectroscopy is emerging as one of the most appealing applications of mid-infrared frequency combs for high-resolution molecular spectroscopy, as it leverages on the unique coherence properties of frequency combs combined with the high sensitivities achievable by mid-infrared molecular spectroscopy. Here we present an on-chip dual-comb source based on mid-infrared quantum cascade laser frequency combs, where two frequency combs are integrated on a single chip. Control of the combs repetition and offset frequencies is obtained by integrating micro-heaters next to each laser. We show that a full control of the dual-comb system is possible, by measuring a multi-heterodyne beating corresponding to an optical bandwidth of 32 cm$^{-1}$ at a center frequency of 1330 cm$^{-1}$ (7.52 $\mu$m), demonstrating that this device is ideal for compact dual-comb spectroscopy systems.
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