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Ilyakov I, Ponomaryov A, Klopf JM, Pashkin A, Deinert JC, de Oliveira TVAG, Evtushenko P, Helm M, Winnerl S, Kovalev S. Field-resolved THz-pump laser-probe measurements with CEP-unstable THz light sources. Opt Express 2022; 30:42141-42154. [PMID: 36366673 DOI: 10.1364/oe.473743] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/23/2022] [Accepted: 10/11/2022] [Indexed: 06/16/2023]
Abstract
Radiation sources with a stable carrier-envelope phase (CEP) are highly demanded tools for field-resolved studies of light-matter interaction, providing access both to the amplitude and phase information of dynamical processes. At the same time, many coherent light sources, including those with outstanding power and spectral characteristics lack CEP stability, and so far could not be used for this type of research. In this work, we present a method enabling linear and non-linear phase-resolved terahertz (THz) -pump laser-probe experiments with CEP-unstable THz sources. THz CEP information for each pulse is extracted using a specially designed electro-optical detection scheme. The method correlates the extracted CEP value for each pulse with the THz-induced response in the parallel pump-probe experiment to obtain an absolute phase-resolved response after proper sorting and averaging. As a proof-of-concept, we demonstrate experimentally field-resolved THz time-domain spectroscopy with sub-cycle temporal resolution using the pulsed radiation of a CEP-unstable infrared free-electron laser (IR-FEL) operating at 13 MHz repetition rate. In spite of the long history of IR-FELs and their unique operational characteristics, no successful realization of CEP-stable operation has been demonstrated yet. Being CEP-unstable, IR-FEL radiation has so far only been used in non-coherent measurements without phase resolution. The technique demonstrated here is robust, operates easily at high-repetition rates and for short THz pulses, and enables common sequential field-resolved time-domain experiments. The implementation of such a technique at IR-FEL user end-stations will facilitate a new class of linear and non-linear experiments for studying coherent light-driven phenomena with increased signal-to-noise ratio.
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Castañeda-Uribe OA, Criollo CA, Winnerl S, Helm M, Avila A. Comparative study of equivalent circuit models for photoconductive antennas. Opt Express 2018; 26:29017-29031. [PMID: 30470070 DOI: 10.1364/oe.26.029017] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/25/2018] [Accepted: 09/18/2018] [Indexed: 06/09/2023]
Abstract
Comparison of equivalent circuit models (ECM) for photoconductive antennas (PCA) represents a challenge due to the multiphysics phenomena involved during PCA operation and the absence of a standardized validation methodology. In this work, currently reported ECMs are compared using a unique set of simulation parameters and validation indicators (THz waveform, optical power saturation, and ECM voltages consistency). The ECM simulations are contrasted with measured THz pulses of an H-shaped 20μm gap PCA at different optical powers (20mW to 220mW). In addition, an alternative two-element ECM that accounts for both space-charge and radiation screening effects is presented and validated using the proposed methodology. The model shows an accurately reproduced THz pulse using a reduced number of circuital elements, which represents an advantage for PCA modeling.
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Piętka B, Bobrovska N, Stephan D, Teich M, Król M, Winnerl S, Pashkin A, Mirek R, Lekenta K, Morier-Genoud F, Schneider H, Deveaud B, Helm M, Matuszewski M, Szczytko J. Doubly Dressed Bosons: Exciton Polaritons in a Strong Terahertz Field. Phys Rev Lett 2017; 119:077403. [PMID: 28949662 DOI: 10.1103/physrevlett.119.077403] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/21/2017] [Indexed: 06/07/2023]
Abstract
We demonstrate the existence of a novel quasiparticle, an exciton in a semiconductor doubly dressed with two photons of different wavelengths: a near infrared cavity photon and terahertz (THz) photon, with the THz coupling strength approaching the ultrastrong coupling regime. This quasiparticle is composed of three different bosons, being a mixture of a matter-light quasiparticle. Our observations are confirmed by a detailed theoretical analysis, treating quantum mechanically all three bosonic fields. The doubly dressed quasiparticles retain the bosonic nature of their constituents, but their internal quantum structure strongly depends on the intensity of the applied terahertz field.
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Affiliation(s)
- B Piętka
- Institute of Experimental Physics, Faculty of Physics, University of Warsaw, ul. Pasteura 5, 02-093 Warsaw, Poland
| | - N Bobrovska
- The Institute of Physics, Polish Academy of Sciences, al. Lotników 32/46, 02-668 Warsaw, Poland
| | - D Stephan
- Institute of Experimental Physics, Faculty of Physics, University of Warsaw, ul. Pasteura 5, 02-093 Warsaw, Poland
- Institute of Ion Beam Physics and Materials Research, HZDR, P.O. Box 510119, 01314 Dresden, Germany
| | - M Teich
- Institute of Ion Beam Physics and Materials Research, HZDR, P.O. Box 510119, 01314 Dresden, Germany
| | - M Król
- Institute of Experimental Physics, Faculty of Physics, University of Warsaw, ul. Pasteura 5, 02-093 Warsaw, Poland
| | - S Winnerl
- Institute of Ion Beam Physics and Materials Research, HZDR, P.O. Box 510119, 01314 Dresden, Germany
| | - A Pashkin
- Institute of Ion Beam Physics and Materials Research, HZDR, P.O. Box 510119, 01314 Dresden, Germany
| | - R Mirek
- Institute of Experimental Physics, Faculty of Physics, University of Warsaw, ul. Pasteura 5, 02-093 Warsaw, Poland
| | - K Lekenta
- Institute of Experimental Physics, Faculty of Physics, University of Warsaw, ul. Pasteura 5, 02-093 Warsaw, Poland
| | - F Morier-Genoud
- Institute of Physics, Ecole Polytechnique Fédérale de Lausanne (EPFL), Station 3, 1015 Lausanne, Switzerland
| | - H Schneider
- Institute of Ion Beam Physics and Materials Research, HZDR, P.O. Box 510119, 01314 Dresden, Germany
| | - B Deveaud
- Institute of Physics, Ecole Polytechnique Fédérale de Lausanne (EPFL), Station 3, 1015 Lausanne, Switzerland
- Ecole Polytechnique, F-91128 Palaiseau, France
| | - M Helm
- Institute of Ion Beam Physics and Materials Research, HZDR, P.O. Box 510119, 01314 Dresden, Germany
| | - M Matuszewski
- The Institute of Physics, Polish Academy of Sciences, al. Lotników 32/46, 02-668 Warsaw, Poland
| | - J Szczytko
- Institute of Experimental Physics, Faculty of Physics, University of Warsaw, ul. Pasteura 5, 02-093 Warsaw, Poland
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Li C, Krauß N, Schäfer G, Ebner L, Kliebisch O, Schmidt J, Winnerl S, Hettich M, Dekorsy T. High-speed asynchronous optical sampling based on GHz Yb:KYW oscillators. Opt Express 2017; 25:9204-9212. [PMID: 28437994 DOI: 10.1364/oe.25.009204] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
A low-cost scheme of high-speed asynchronous optical sampling based on Yb:KYW oscillators is reported. Two GHz diode-pumped oscillators with a slight pulse repetition rate offset serve as pump and probe source, respectively. The temporal resolution of this system is limited to 500 fs mainly by the pulse duration of the oscillators and also by relative timing jitter between the oscillators. A near-shot-noise noise floor around 10-6 (∆R/R) is obtained within a data acquisition time of a few seconds. The performance of the system is demonstrated by measurements of coherent acoustic phonons in a semiconductor sample that resembles a semiconductor saturable absorber mirror or an optically pumped semiconductor chip.
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König-Otto JC, Mittendorff M, Winzer T, Kadi F, Malic E, Knorr A, Berger C, de Heer WA, Pashkin A, Schneider H, Helm M, Winnerl S. Slow Noncollinear Coulomb Scattering in the Vicinity of the Dirac Point in Graphene. Phys Rev Lett 2016; 117:087401. [PMID: 27588881 DOI: 10.1103/physrevlett.117.087401] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/13/2015] [Indexed: 06/06/2023]
Abstract
The Coulomb scattering dynamics in graphene in energetic proximity to the Dirac point is investigated by polarization resolved pump-probe spectroscopy and microscopic theory. Collinear Coulomb scattering rapidly thermalizes the carrier distribution in k directions pointing radially away from the Dirac point. Our study reveals, however, that, in almost intrinsic graphene, full thermalization in all directions relying on noncollinear scattering is much slower. For low photon energies, carrier-optical-phonon processes are strongly suppressed and Coulomb mediated noncollinear scattering is remarkably slow, namely on a ps time scale. This effect is very promising for infrared and THz devices based on hot carrier effects.
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Affiliation(s)
- J C König-Otto
- Helmholtz-Zentrum Dresden-Rossendorf, P.O. Box 510119, 01314 Dresden, Germany
- Technische Universität Dresden, 01062 Dresden, Germany
| | - M Mittendorff
- University of Maryland, College Park, Maryland 20742, USA
| | - T Winzer
- Technische Universität Berlin, Hardenbergstraße 36, 10623 Berlin, Germany
| | - F Kadi
- Technische Universität Berlin, Hardenbergstraße 36, 10623 Berlin, Germany
| | - E Malic
- Chalmers University of Technology, SE-41296 Göteborg, Sweden
| | - A Knorr
- Technische Universität Berlin, Hardenbergstraße 36, 10623 Berlin, Germany
| | - C Berger
- Georgia Institute of Technology, Atlanta, Georgia 30332, USA
- Institut Néel, CNRS-Université Alpes, 38042 Grenoble, France
| | - W A de Heer
- Georgia Institute of Technology, Atlanta, Georgia 30332, USA
| | - A Pashkin
- Helmholtz-Zentrum Dresden-Rossendorf, P.O. Box 510119, 01314 Dresden, Germany
| | - H Schneider
- Helmholtz-Zentrum Dresden-Rossendorf, P.O. Box 510119, 01314 Dresden, Germany
| | - M Helm
- Helmholtz-Zentrum Dresden-Rossendorf, P.O. Box 510119, 01314 Dresden, Germany
- Technische Universität Dresden, 01062 Dresden, Germany
| | - S Winnerl
- Helmholtz-Zentrum Dresden-Rossendorf, P.O. Box 510119, 01314 Dresden, Germany
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6
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Schmidt J, Winnerl S, Seidel W, Bauer C, Gensch M, Schneider H, Helm M. Single-pulse picking at kHz repetition rates using a Ge plasma switch at the free-electron laser FELBE. Rev Sci Instrum 2015; 86:063103. [PMID: 26133824 DOI: 10.1063/1.4921864] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
We demonstrate a system for picking of mid-infrared and terahertz (THz) radiation pulses from the free-electron laser (FEL) FELBE operating at a repetition rate of 13 MHz. Single pulses are reflected by a dense electron-hole plasma in a Ge slab that is photoexcited by amplified near-infrared (NIR) laser systems operating at repetition rates of 1 kHz and 100 kHz, respectively. The peak intensity of picked pulses is up to 400 times larger than the peak intensity of residual pulses. The required NIR fluence for picking pulses at wavelengths in the range from 5 μm to 30 μm is discussed. In addition, we show that the reflectivity of the plasma decays on a time scale from 100 ps to 1 ns dependent on the wavelengths of the FEL and the NIR laser. The plasma switch enables experiments with the FEL that require high peak power but lower average power. Furthermore, the system is well suited to investigate processes with decay times in the μs to ms regime, i.e., much longer than the 77 ns long pulse repetition period of FELBE.
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Affiliation(s)
- J Schmidt
- Institute of Ion Beam Physics and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf, 01314 Dresden, Germany
| | - S Winnerl
- Institute of Ion Beam Physics and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf, 01314 Dresden, Germany
| | - W Seidel
- Institute of Ion Beam Physics and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf, 01314 Dresden, Germany
| | - C Bauer
- Institute of Radiation Physics, Helmholtz-Zentrum Dresden-Rossendorf, 01314 Dresden, Germany
| | - M Gensch
- Institute of Ion Beam Physics and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf, 01314 Dresden, Germany
| | - H Schneider
- Institute of Ion Beam Physics and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf, 01314 Dresden, Germany
| | - M Helm
- Institute of Ion Beam Physics and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf, 01314 Dresden, Germany
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7
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Kadi F, Winzer T, Malic E, Knorr A, Göttfert F, Mittendorff M, Winnerl S, Helm M. Microscopic description of intraband absorption in graphene: the occurrence of transient negative differential transmission. Phys Rev Lett 2014; 113:035502. [PMID: 25083654 DOI: 10.1103/physrevlett.113.035502] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/04/2014] [Indexed: 05/23/2023]
Abstract
We present a microscopic explanation of the controversially discussed transient negative differential transmission observed in degenerate optical pump-probe measurements in graphene. Our approach is based on the density matrix formalism allowing a time- and momentum-resolved study of carrier-light, carrier-carrier, and carrier-phonon interaction on microscopic footing. We show that phonon-assisted optical intraband transitions give rise to transient absorption in the optically excited hot carrier system counteracting pure absorption bleaching of interband transitions. While interband transition bleaching is relevant in the first hundreds of fs after the excitation, intraband absorption sets in at later times. In particular, in the low excitation regime, these intraband absorption processes prevail over the absorption bleaching resulting in a zero crossing of the differential transmission. Our findings are in good qualitative agreement with recent experimental pump-probe studies.
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Affiliation(s)
- Faris Kadi
- Institut für Theoretische Physik, Nichtlineare Optik und Quantenelektronik, Technische Universität Berlin, Hardenbergstr. 36, 10623 Berlin, Germany
| | - Torben Winzer
- Institut für Theoretische Physik, Nichtlineare Optik und Quantenelektronik, Technische Universität Berlin, Hardenbergstr. 36, 10623 Berlin, Germany and Department of Materials Science and Engineering, Yonsei University, Seoul 120-749, Korea
| | - Ermin Malic
- Institut für Theoretische Physik, Nichtlineare Optik und Quantenelektronik, Technische Universität Berlin, Hardenbergstr. 36, 10623 Berlin, Germany
| | - Andreas Knorr
- Institut für Theoretische Physik, Nichtlineare Optik und Quantenelektronik, Technische Universität Berlin, Hardenbergstr. 36, 10623 Berlin, Germany
| | - F Göttfert
- Helmholtz-Zentrum Dresden-Rossendorf, P.O. Box 510119, D-01314 Dresden, Germany
| | - M Mittendorff
- Helmholtz-Zentrum Dresden-Rossendorf, P.O. Box 510119, D-01314 Dresden, Germany and Technische Universität Dresden, 01062 Dresden, Germany
| | - S Winnerl
- Helmholtz-Zentrum Dresden-Rossendorf, P.O. Box 510119, D-01314 Dresden, Germany
| | - M Helm
- Helmholtz-Zentrum Dresden-Rossendorf, P.O. Box 510119, D-01314 Dresden, Germany and Technische Universität Dresden, 01062 Dresden, Germany
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8
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Preu S, Mittendorff M, Winnerl S, Lu H, Gossard AC, Weber HB. Ultra-fast transistor-based detectors for precise timing of near infrared and THz signals. Opt Express 2013; 21:17941-17950. [PMID: 23938666 DOI: 10.1364/oe.21.017941] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
A whole class of two-color experiments involves intense, short Terahertz radiation pulses. A fast and moderately sensitive detector capable to resolve both near-infrared and Terahertz pulses at the same time is highly desirable. Here we present the first detector of this kind. The detector element is a GaAs-based field effect transistor operated at room temperature. THz detection is successfully demonstrated at frequencies up to 4.9 THz. The THz detection time constant is shorter than 30 ps, the optical time constant is 150 ps. This detector is ideally suited for precise, simultaneous resolution of optical and THz pulses and for pulse characterization of high-power THz pulses up to tens of kW peak power levels. The dynamic range of the detector is as large as 65±3dB/Hz, enabling applications in a large variety of experiments and setups, also including table-top systems.
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Affiliation(s)
- S Preu
- Univ. of Erlangen-Nuremberg, Germany.
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9
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Beck M, Rousseau I, Klammer M, Leiderer P, Mittendorff M, Winnerl S, Helm M, Gol'tsman GN, Demsar J. Transient increase of the energy gap of superconducting NbN thin films excited by resonant narrow-band terahertz pulses. Phys Rev Lett 2013; 110:267003. [PMID: 23848912 DOI: 10.1103/physrevlett.110.267003] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/21/2012] [Indexed: 06/02/2023]
Abstract
Observations of radiation-enhanced superconductivity have thus far been limited to a few type-I superconductors (Al, Sn) excited at frequencies between the inelastic scattering rate and the superconducting gap frequency 2Δ/h. Utilizing intense, narrow-band, picosecond, terahertz pulses, tuned to just below and above 2Δ/h of a BCS superconductor NbN, we demonstrate that the superconducting gap can be transiently increased also in a type-II dirty-limit superconductor. The effect is particularly pronounced at higher temperatures and is attributed to radiation induced nonthermal electron distribution persisting on a 100 ps time scale.
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Affiliation(s)
- M Beck
- Department of Physics and Center for Applied Photonics, University of Konstanz, D-78457, Germany
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10
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Dienst A, Casandruc E, Fausti D, Zhang L, Eckstein M, Hoffmann M, Khanna V, Dean N, Gensch M, Winnerl S, Seidel W, Pyon S, Takayama T, Takagi H, Cavalleri A. Optical excitation of Josephson plasma solitons in a cuprate superconductor. Nat Mater 2013; 12:535-541. [PMID: 23524373 DOI: 10.1038/nmat3580] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/24/2011] [Accepted: 01/28/2013] [Indexed: 06/02/2023]
Abstract
Josephson plasma waves are linear electromagnetic modes that propagate along the planes of cuprate superconductors, sustained by interlayer tunnelling supercurrents. For strong electromagnetic fields, as the supercurrents approach the critical value, the electrodynamics become highly nonlinear. Josephson plasma solitons (JPSs) are breather excitations predicted in this regime, bound vortex-antivortex pairs that propagate coherently without dispersion. We experimentally demonstrate the excitation of a JPS in La1.84Sr0.16CuO4, using intense narrowband radiation from an infrared free-electron laser tuned to the 2-THz Josephson plasma resonance. The JPS becomes observable as it causes a transparency window in the opaque spectral region immediately below the plasma resonance. Optical control of magnetic-flux-carrying solitons may lead to new applications in terahertz-frequency plasmonics, in information storage and transport and in the manipulation of high-Tc superconductivity.
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Affiliation(s)
- A Dienst
- Department of Physics, Clarendon Laboratory, University of Oxford, Oxford, UK
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Rice WD, Kono J, Zybell S, Winnerl S, Bhattacharyya J, Schneider H, Helm M, Ewers B, Chernikov A, Koch M, Chatterjee S, Khitrova G, Gibbs HM, Schneebeli L, Breddermann B, Kira M, Koch SW. Observation of forbidden exciton transitions mediated by Coulomb interactions in photoexcited semiconductor quantum wells. Phys Rev Lett 2013; 110:137404. [PMID: 23581371 DOI: 10.1103/physrevlett.110.137404] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/18/2012] [Revised: 11/27/2012] [Indexed: 06/02/2023]
Abstract
We use terahertz pulses to induce resonant transitions between the eigenstates of optically generated exciton populations in a high-quality semiconductor quantum well sample. Monitoring the excitonic photoluminescence, we observe transient quenching of the 1s exciton emission, which we attribute to the terahertz-induced 1s-to-2p excitation. Simultaneously, a pronounced enhancement of the 2s exciton emission is observed, despite the 1s-to-2s transition being dipole forbidden. A microscopic many-body theory explains the experimental observations as a Coulomb-scattering mixing of the 2s and 2p states, yielding an effective terahertz transition between the 1s and 2s populations.
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Affiliation(s)
- W D Rice
- Department of Electrical and Computer Engineering, Rice University, Houston, Texas 77005, USA
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12
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Winnerl S, Göttfert F, Mittendorff M, Schneider H, Helm M, Winzer T, Malic E, Knorr A, Orlita M, Potemski M, Sprinkle M, Berger C, de Heer WA. Time-resolved spectroscopy on epitaxial graphene in the infrared spectral range: relaxation dynamics and saturation behavior. J Phys Condens Matter 2013; 25:054202. [PMID: 23441326 DOI: 10.1088/0953-8984/25/5/054202] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
We present the results of pump–probe experiments on multilayer graphene samples performed in a wide spectral range, namely from the near infrared (photon energy 1.5 eV) to the terahertz (photon energy 8 meV) spectral range. In the near infrared, exciting carriers and probing at higher photon energies provides direct evidence for a hot carrier distribution. Furthermore, spectroscopic signatures of the highly doped graphene layers at the interface to SiC are observed in the near-infrared range. In the mid-infrared range, the various relaxation mechanisms, in particular scattering via optical phonons and Auger-type processes, are identified by comparing the experimental results to microscopic modeling. Changes from induced transmission to induced absorption are attributed to probing above or below the Fermi edge of the graphene layers. This effect occurs for certain photon energies in the near-infrared range, where it is related to highly doped graphene layers at the interface to SiC, and in the far-infrared range for the quasi-intrinsic graphene layers. In addition to the relaxation dynamics, the saturation of pump-induced bleaching of graphene is studied. Here a quadratic dependence of the saturation fluence on the pump photon energy in the infrared spectral range is revealed.
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Affiliation(s)
- S Winnerl
- Helmholtz-Zentrum Dresden-Rossendorf, PO Box 510119, D-01314 Dresden, Germany.
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13
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Winnerl S, Orlita M, Plochocka P, Kossacki P, Potemski M, Winzer T, Malic E, Knorr A, Sprinkle M, Berger C, de Heer WA, Schneider H, Helm M. Carrier relaxation in epitaxial graphene photoexcited near the Dirac point. Phys Rev Lett 2011; 107:237401. [PMID: 22182122 DOI: 10.1103/physrevlett.107.237401] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/19/2011] [Indexed: 05/31/2023]
Abstract
We study the carrier dynamics in epitaxially grown graphene in the range of photon energies from 10 to 250 meV. The experiments complemented by microscopic modeling reveal that the carrier relaxation is significantly slowed down as the photon energy is tuned to values below the optical-phonon frequency; however, owing to the presence of hot carriers, optical-phonon emission is still the predominant relaxation process. For photon energies about twice the value of the Fermi energy, a transition from pump-induced transmission to pump-induced absorption occurs due to the interplay of interband and intraband processes.
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Affiliation(s)
- S Winnerl
- Helmholtz-Zentrum Dresden-Rossendorf, P.O. Box 510119, 01314 Dresden, Germany.
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Bhattacharyya J, Wagner M, Zybell S, Winnerl S, Stehr D, Helm M, Schneider H. Simultaneous time and wavelength resolved spectroscopy under two-colour near infrared and terahertz excitation. Rev Sci Instrum 2011; 82:103107. [PMID: 22047280 DOI: 10.1063/1.3653394] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
Time and wavelength resolved spectroscopy requires optical sources emitting very short pulses and a fast detection mechanism capable of measuring the evolution of the output spectrum as a function of time. We use table-top Ti:sapphire lasers and a free-electron laser (FEL) emitting ps pulses as excitation sources and a streak camera coupled to a spectrometer for detection. One of the major aspects of this setup is the synchronization of pulses from the two lasers which we describe in detail. Optical properties of the FEL pulses are studied by autocorrelation and electro-optic sampling measurements. We discuss the advantages of using this setup to perform photoluminescence quenching in semiconductor quantum wells and quantum dots. Carrier redistribution due to pulsed excitation in these heterostructures can be investigated directly. Sideband generation in quantum wells is also studied where the intense FEL pulses facilitate the detection of the otherwise weak nonlinear effect.
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Affiliation(s)
- J Bhattacharyya
- Institute of Ion Beam Physics and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf, 01314 Dresden, Germany.
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15
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Drachenko O, Winnerl S, Schneider H, Helm M, Wosnitza J, Leotin J. Compact magnetospectrometer for pulsed magnets based on infrared quantum cascade lasers. Rev Sci Instrum 2011; 82:033108. [PMID: 21456719 DOI: 10.1063/1.3556441] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
In this paper we present a portable quantum cascade laser (QCL) based infrared magnetospectrometer covering the spectral range from 5 to 120 μm. The variation of the excitation wavelength is enabled by an easy change of the QCL plug-in modules, while the use of any other external source is also possible. The performance of the setup is illustrated via cyclotron-resonance studies under pulsed magnetic fields up to 60 T.
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Affiliation(s)
- O Drachenko
- Institute of Ion-Beam Physics and Materials Research, Helmholtz-Zentrum Dresden-Rossendorf, 01314 Dresden, Germany.
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Peter F, Winnerl S, Schneider H, Helm M. Excitation wavelength dependence of phase matched terahertz emission from a GaAs slab. Opt Express 2010; 18:19574-19580. [PMID: 20940853 DOI: 10.1364/oe.18.019574] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
We report on phase matched THz emission from GaAs using the anomalous dispersion introduced by optical phonon absorption at the reststrahlenband in GaAs. For this system tunability of the emitted THz frequencies by changing the near infrared excitation wavelength is predicted. We investigate this phenomenon for an oversized double metallized GaAs waveguide. A shift in the THz spectra is observed when the near-infrared wavelength is varied. Enhanced emission is found when phase matching is achieved at 1.4 µm.
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Affiliation(s)
- F Peter
- Institute of Ion Beam Physics and Materials Research, Forschungszentrum Dresden Rossendorf, Dresden, Germany.
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17
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Beck M, Schäfer H, Klatt G, Demsar J, Winnerl S, Helm M, Dekorsy T. Impulsive terahertz radiation with high electric fields from an amplifier-driven large-area photoconductive antenna. Opt Express 2010; 18:9251-9257. [PMID: 20588772 DOI: 10.1364/oe.18.009251] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
We report on the generation of impulsive terahertz (THz) radiation with 36 kV/cm vacuum electric field (1.5 mW average thermal power) at 250 kHz repetition rate and a high NIR-to-THz conversion efficiency of 2 x 10(-3). This is achieved by photoexciting biased large-area photoconductive emitter with NIR fs pulses of microJ pulse energy. We demonstrate focussing of the THz beam by tailoring the pulse front of the exciting laser beam without any focussing element for the THz beam. A high dynamic range of 10(4) signal-to-noise is obtained with an amplifier based system.
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Affiliation(s)
- M Beck
- Department of Physics and Center for Applied Photonics, University of Konstanz, D-78457 Konstanz, Germany.
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18
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Zibik EA, Grange T, Carpenter BA, Porter NE, Ferreira R, Bastard G, Stehr D, Winnerl S, Helm M, Liu HY, Skolnick MS, Wilson LR. Long lifetimes of quantum-dot intersublevel transitions in the terahertz range. Nat Mater 2009; 8:803-807. [PMID: 19684587 DOI: 10.1038/nmat2511] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/15/2009] [Accepted: 07/14/2009] [Indexed: 05/28/2023]
Abstract
Carrier relaxation is a key issue in determining the efficiency of semiconductor optoelectronic device operation. Devices incorporating semiconductor quantum dots have the potential to overcome many of the limitations of quantum-well-based devices because of the predicted long quantum-dot excited-state lifetimes. For example, the population inversion required for terahertz laser operation in quantum-well-based devices (quantum-cascade lasers) is fundamentally limited by efficient scattering between the laser levels, which form a continuum in the plane of the quantum well. In this context, semiconductor quantum dots are a highly attractive alternative for terahertz devices, because of their intrinsic discrete energy levels. Here, we present the first measurements, and theoretical description, of the intersublevel carrier relaxation in quantum dots for transition energies in the few terahertz range. Long intradot relaxation times (1.5 ns) are found for level separations of 14 meV (3.4 THz), decreasing very strongly to approximately 2 ps at 30 meV (7 THz), in very good agreement with our microscopic theory of the carrier relaxation process. Our studies pave the way for quantum-dot terahertz device development, providing the fundamental knowledge of carrier relaxation times required for optimum device design.
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Affiliation(s)
- E A Zibik
- [1] Department of Physics and Astronomy, University of Sheffield, Sheffield S3 7RH, UK [2] Present addresses: Oclaro (Switzerland) AG, Binzstrasse 17, CH-8045 Zürich, Switzerland (E.A.Z.); Walter Schottky Institut, Technische Universität München, 85748 Garching, Germany (T.G.); Department of Electronic & Electrical Engineering, University College London, London WC1E 7JE, UK (H.Y.L.) [3] These authors contributed equally to this work
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19
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Schneider H, Liu HC, Winnerl S, Song CY, Walther M, Helm M. Terahertz two-photon quantum well infrared photodetector. Opt Express 2009; 17:12279-12284. [PMID: 19654629 DOI: 10.1364/oe.17.012279] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
A two-photon detector based on intersubband transitions in GaAs/AlGaAs quantum wells operating in the Terahertz regime below the Reststrahlenband is reported. Resonantly enhanced optical nonlinearities enables sensitive quadratic detection at pJ pulse energies. We demonstrate its use in a quadratic autocorrelator for far-infrared picosecond pulses at around 7 THz.
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Affiliation(s)
- H Schneider
- Forschungszentrum Dresden Rossendorf, Institute of Ion Beam Physics and Materials Research, P O Box 510119, D-01314 Dresden, Germany.
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20
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Winnerl S, Zimmermann B, Peter F, Schneider H, Helm M. Terahertz Bessel-Gauss beams of radial and azimuthal polarization from microstructured photoconductive antennas. Opt Express 2009; 17:1571-1576. [PMID: 19188986 DOI: 10.1364/oe.17.001571] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
We report on emission and detection of pulsed terahertz radiation of radial and azimuthal polarization by microstructured photoconductive antennas. To this end the electrode geometry of the emitter is inverse to the desired THz field pattern and a second periodic structure prevents destructive interference effects. Beam profiles of freely propagating THz waves are studied for divergent and refocused beams. They can be well described as the lowest order Bessel-Gauss modes with a divergence comparable to linearly polarized Gaussian beams. Additionally, mode sensitive detection is demonstrated for radially polarized radiation.
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Affiliation(s)
- S Winnerl
- Institute of Ion Beam Physics and Materials Research, Forschungszentrum Dresden Rossendorf, Dresden, Germany.
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21
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Kehr SC, Cebula M, Mieth O, Härtling T, Seidel J, Grafström S, Eng LM, Winnerl S, Stehr D, Helm M. Anisotropy contrast in phonon-enhanced apertureless near-field microscopy using a free-electron laser. Phys Rev Lett 2008; 100:256403. [PMID: 18643683 DOI: 10.1103/physrevlett.100.256403] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/20/2007] [Revised: 05/14/2008] [Indexed: 05/26/2023]
Abstract
We demonstrate the imaging of ferroelectric domains in BaTiO3, using an infrared-emitting free-electron laser as a tunable optical source for scattering scanning near-field optical microscopy and spectroscopy. When the laser is tuned into the spectral vicinity of a phonon resonance, ferroelectric domains can be resolved due to the anisotropy of the dielectric properties of the material. Slight detuning of the wavelength gives rise to a contrast reversal clearly evidencing the resonant character of the excitation. The near-field domain contrast shows that the orientation of the dielectric tensor with respect to the sample surface has a clear influence on the near-field signal.
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Affiliation(s)
- S C Kehr
- Institute of Applied Photophysics, Technische Universität Dresden, D-01062 Dresden, Germany
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22
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von Ribbeck HG, Brehm M, van der Weide DW, Winnerl S, Drachenko O, Helm M, Keilmann F. Spectroscopic THz near-field microscope. Opt Express 2008; 16:3430-3438. [PMID: 18542434 DOI: 10.1364/oe.16.003430] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
We demonstrate a scattering-type scanning near-field optical microscope (s-SNOM) with broadband THz illumination. A cantilevered W tip is used in tapping AFM mode. The direct scattering spectrum is obtained and optimized by asynchronous optical sampling (ASOPS), while near-field scattering is observed by using a space-domain delay stage and harmonic demodulation of the detector signal. True near-field interaction is determined from the approach behavior of the tip to Au samples. Scattering spectra of differently doped Si are presented.
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Affiliation(s)
- H-G von Ribbeck
- Max-Planck-Institut für Biochemie and Center for Nanoscience, 82152 Martinsried (München), Germany.
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Bartels A, Thoma A, Janke C, Dekorsy T, Dreyhaupt A, Winnerl S, Helm M. High-resolution THz spectrometer with kHz scan rates. Opt Express 2006; 14:430-437. [PMID: 19503357 DOI: 10.1364/opex.14.000430] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
We demonstrate a rapid scanning high-resolution THz spectrometer capable of acquiring THz field transients with 1 ns duration without mechanical delay line. The THz spectrometer is based on two 1-GHz Ti:sapphire femtosecond lasers which are linked with a fixed repetition rate difference in order to perform high-speed asynchronous optical sampling. One laser drives a high-efficiency large-area GaAs based THz emitter, the other laser is used for electro-optic detection of the emitted THz-field. At a scan rate of 9 kHz a time resolution of 230 fs is accomplished. High-resolution spectra from 50 GHz up to 3 THz are obtained and water absorption lines with a width of 11 GHz are observed. The use of femtosecond lasers with 1 GHz repetition rate is essential to obtain rapid scanning and high time-resolution at the same time.
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