Techniques de recherche
Techniques de recherche
Photoinduced phase transitions
The bistable nature of spin crossover (SCO) molecular materials coupled to their very high sensitivity to light stimuli is of particular interest for the development of data recording media. Many of these compounds possess a thermal hysteresis loop at room temperature, leading to the existence of two metastable spin states. By means of a pulsed laser excitation it is then possible to switch back and forth between these two metastable states, making it possible to record and to erase optical information in these compounds. Our research fits into this framework, focusing especially on the understanding of the basic mechanisms governing the spin transition, from the molecular to the macroscopic scale. To this end, we perform Ultrafast time-resolved spectroscopy experiments in the visible, NIR and THz ranges. The aim is to link these mechanisms to the composition of the system in order to synthesize compounds with suitable properties for practical applications. This work is made in collaboration with chemists from the Institut de Chimie de la Matière Condensée de Bordeaux (ICMCB).
Generation and shaping of THz pulses – Coherent control
Many phenomena in materials science, physics, chemistry, biology and medicine involve fundamental processes with a spectral signature in the THz range. However, for many years, these processes have been little studied due to the lack of high quality THz sources. Fortunately, the recent developments in THz technology have filled this so-called THz gap. With the emergence of reliable THz sources, the need for arbitrarily shaped THz pulses dedicated to specific applications like communications, signal processing, spectroscopy or coherent/optimal control is more and more felt.
To this end, several methods have been developed to extend the generation of arbitrary pulse shapes from the visible and mid-infrared spectral region up to the THz range. All are based on the generation of THz pulses by excitation of different types of emitters with spatially and/or temporally shaped optical pulses. In our group, we focus our attention on the generation, tuning and shaping of narrow-band THz pulses by optical rectification of shaped optical pulses. The aim is to generate intense shaped THz pulses to control photophysical processes like phase transitions in SCO compounds or to implement the methods of multi-dimensional spectroscopy in the THz range.
Photonics and ULtrafast Spectrocopy.
Informations à venir…
- S. Vidal, J. Degert, M. Tondusson, E. Freysz, J. Oberlé, ‘‘Optimized terahertz generation via optical rectification in ZnTe crystals’’, J. Opt. Soc. Am. B. 31 (1), 149-153 (2014).
- W. Hellel, A. Ould Hamouda, J. Degert, J. F. Létard, E. Freysz, ‘‘Switching of spin-state complexes induced by the interaction of a laser beam with their host matrix’’, Appl. Phys. Lett. 103, 143304 (2013).
- G. Gallé, C. Etrillard, J. Degert, F. Guillaume, J.-F. Létard, E. Freysz, ‘‘Study of the fast photoswitching of spin crossover nanoparticles outside and inside their thermal hysteresis loop,’’ Appl. Phys. Lett. 102, 063302 (2013).
- B. Viquerat, J. Degert, J. F. Létard, E. Freysz, ‘‘Relaxation oscillations during the laser-induced spin state transition of a [Fe(PM-BiA)2(NCS)2] complex,’’ Phys. Rev. B 87, 024303 (2013).
- M .Tondusson, J. Degert, F. Couchot, X. Sarrazin, M. Urban, J. Oberlé, E. Freysz, ‘‘Group index determination by pulse delay measurements and dispersion study in the zero dispersion region of fused silica,’’ J. Opt. Soc. Am. B 29, 2797-2802 (2012).
- B. Viquerat, J. Degert, M. Tondusson, C. Mauriac, J.F. Létard, E. Freysz, ‘‘Time-Domain Terahertz Spectroscopy of Spin State Transition in [Fe(NH2-trz)3]2+ Spin Crossover Compounds, ’’ Appl. Phys. Lett. 99, 061908 (2011).
- S. Vidal, J. Degert, J. Oberlé, E. Freysz, ‘‘Impact of dispersion, free carriers and two-photon absorption on the generation of intense THz pulses in ZnTe crystals,’’ Appl. Phys. Lett. 98, 191103 (2011).
- G. Gallé, J. Degert, C. Mauriac, C. Etrillard, J.-F. Létard, E. Freysz, ‘‘Nanosecond study of spin state transition induced by a single nanosecond laser shot on [Fe(NH2-trz)3] compounds inside and outside their thermal hysteresis loops,’’ Chem. Phys. Lett. 500, 18-22 (2010).
- E. Freysz, J. Degert, ‘‘Nonlinear optics : Terahertz Kerr effect,’’ Nature Photonics 4 (3), 131-132 (2010).
- S. Vidal, J. Degert, J. Oberlé, E. Freysz, ‘‘Femtosecond optical pulse shaping for tunable terahertz pulses generation,’’ J. Opt. Soc. Am. B. 27 (5), 1044-1050 (2010).
- O. Fouché, J. Degert, G. Jonusauskas, N. Daro, J.-F. Létard, E. Freysz, ‘‘Mechanism for optical switching of the spin crossover [Fe(NH2-trz)3](Br)2•3H2O compound at room temperature,’’ Phys. Chem. Chem. Phys. 12 (12), 3044-3052 (2010).
- G. Gallé, D. Deldicque, J. Degert, Th. Forestier, J.-F. Létard, E. Freysz, ‘‘Room temperature study of the optical switching of a spin crossover compound inside its thermal hysteresis loop,’’ Appl. Phys. Lett. 96 (4), 041907 (2010).
- O. Fouché, J. Degert, G. Jonusauskas, C. Baldé, C. Desplanche, J.-F. Létard, E. Freysz, ‘‘Laser induced spin state transition : Spectral and temporal evolution,’’ Chem. Phys. Lett. 469, 274-278 (2009).
- C. D’Amico, M. Tondusson, J. Degert, E. Freysz, ‘‘Tuning and focusing THz pulses by shaping the pump laser beam profile in a nonlinear crystal,’’ Optics Express 17 (2), 592-597 (2009).
- P. Mounaix, E. Freysz, J. Degert, N. Daro, J.-F. Létard, P. Kuzel, V. Vigneras, L. Oyenhart, “One-dimensional tunable photonic crystals with spin crossover material for the terahertz range,” Appl. Phys. Lett. 89 (17), 174105 (2006).
- P. Mounaix , N. Lascoux, J. Degert, E. Freysz, A. Kobayashi, N. Daro, J.-F. Létard, “Dielectric characterization of [(Fe(NH2)Trz2)]Br2•H2O thermal spin crossover compound by terahertz time domain spectroscopy,” Appl. Phys. Lett. 87 (24), 1-3 (2005).
- J. Degert, N. Lascoux, S. Montant, S. Létard, E. Freysz, G. Chastanet, J.-F. Létard, “Complete temperature study of the relaxation from the high-spin state to low-spin state in a strongly cooperative spin crossover compound,” Chem. Phys. Lett. 415, 206-210 (2005).
- W. Wohlleben, J. Degert, B. Chatel, M. Motzkus, B. Girard, “Coherent transients as highly sensitive probes for femtosecond pulse shapers,” Appl. Phys. B 79, 435-439 (2004).
- B. Chatel, J. Degert, B. Girard, “Role of quadratic and cubic spectral phases in ladder climbing with ultrashort pulses,” Phys. Rev. A 70, 053414 (2004).
- B. Chatel, J. Degert, S. Stock, B. Girard, “Competition between sequential and direct paths in a two-photon transition,” Phys. Rev. A 68, 041402 (2003).
- J. Degert, C. Meier, B. Chatel, B. Girard, “Coherent control of matter wave interferences in molecular predissociation,” Phys. Rev. A 67, 041402 (2003).
- J. Degert, W. Wohlleben, B. Chatel, M. Motzkus, B. Girard, “Realization of a time-domain Fresnel lens with Coherent control,” Phys. Rev. Lett. 89 (20), 203003 (2002).
- S. Zamith, J. Degert, S. Stock, B. de Beauvoir, V. Blanchet, M. A. Bouchene, B. Girard, “Observation of Coherent Transients in Ultrashort Chirped Excitation of an undamped Two-Level System,” Phys. Rev. Lett. 87 (3), 033001 (2001).
- J. Degert, C. Meier, B. Girard, M.J.J. Vrakking, “Time-dependent fragment distributions detected via pump-probe ionisation : a theoritical approach,” Eur. Phys. J. D 14, 257-265 (2001).
Since September 2003 : Associate Professor at the Université Bordeaux 1.
2003 : Post-doctoral research at the Max-Planck-Institut für Quantenoptik, Garching, Germany.
2002 – 2003 : Attaché temporaire d’enseignement et de recherche at the Université Paul Sabatier, Toulouse.
1999 – 2002 : PhD in Atomic and Molecular Physics, Université Paul Sabatier, Toulouse, Supervisors : B. Chatel, B. Girard (thesis file).
- First year :
- P0SE1004 : Physics 1-Geometric Optics (lecture, tutorial, practical work).
- Second year :
- Third year :
- Q1PY6W31 : Instruments and Physical Optics (tutorial, practical work).
Preparation for the contest of access to paramedical schools
- P1TC1006 : Physics (electricity and magnetism, waves, quantum physics) (lecture, tutorial).
Laboratoire Ondes et Matière d’aquitaine (LOMA)
351 cours de la libération
33405 Talence Cedex
Phone : + 33 (0)5 40 00 89 97
Fax : + 33 (0)5 40 00 69 70