Eighth International Conference on Ultrafast Phenomena最新文献

{"title":"Ultrafast Dynamics of Solid C60","authors":"S. Dexheimer, D. Mittleman, R. Schoenlein, W. Vareka, X. Xiang, A. Zettl, C. Shank","doi":"10.1007/978-3-642-84910-7_19","DOIUrl":"https://doi.org/10.1007/978-3-642-84910-7_19","url":null,"abstract":"","PeriodicalId":242710,"journal":{"name":"Eighth International Conference on Ultrafast Phenomena","volume":"73 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127666361","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Squeezing of the Molecular Vibrations by Femtosecond Laser Pulses","authors":"A. Vinogradov, J. Janszky","doi":"10.1007/978-3-642-84910-7_24","DOIUrl":"https://doi.org/10.1007/978-3-642-84910-7_24","url":null,"abstract":"","PeriodicalId":242710,"journal":{"name":"Eighth International Conference on Ultrafast Phenomena","volume":"66 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129831855","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Generation of Pulsed High Power Far Infrared Radiation","authors":"D. Dykaar","doi":"10.1364/up.1992.mc15","DOIUrl":"https://doi.org/10.1364/up.1992.mc15","url":null,"abstract":"Using large aperture photoconductive switches(1) and interferometric detection(2), we have measured pulses of far infrared radiation (FIR) in excess of 100 nJ per pulse with pulse widths of 600 fs (FWHM). This is the most sub-picosecond FIR generated to date. Detection was accomplished using a pyroelectric detector(2).","PeriodicalId":242710,"journal":{"name":"Eighth International Conference on Ultrafast Phenomena","volume":"237 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121182473","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Impulsive Stimulated Raman Scattering Study of Soft Mode Dynamics in Ferroelectric Crystals","authors":"G. Wiederrecht, T. P. Dougherty, K. Nelson","doi":"10.1364/up.1992.tha5","DOIUrl":"https://doi.org/10.1364/up.1992.tha5","url":null,"abstract":"Soft Modes, ISRS, and Perovskite Ferroelectrics The dynamics of cooperative ordering in crystals near structural phase transitions have long been elusive. Most picosecond and femtosecond time-resolved measurements have involved rapid laser heating of a sample whose phase transition (e.g. melting) dynamics are then monitored1. In this case many lattice degrees of freedom are excited, and little information is provided about the roles or dynamics of particular lattice motions. In structural phase transitions, the order parameter is described by one or a very few specific (\"soft\") lattice modes whose motions bring crystalline constituents from their initial positions into their positions in a new crystalline phase. Experimental characterization of the dynamics is possible in some cases through Raman spectroscopy, but often the highly damped character of the soft mode leads to a central peak in the Raman spectrum which cannot be analyzed accurately. In many cases it is not even possible to tell whether the ordering motion is a heavily damped vibration, Debye relaxation, or some combination of the two. This information is essential for understanding the microscopic mechanism of a transition since vibrational or relaxational character is an indication of ionic motion within a single potential energy minimum (i.e. a displacive transition) or hopping between different sites (an order-disorder transition) respectively.","PeriodicalId":242710,"journal":{"name":"Eighth International Conference on Ultrafast Phenomena","volume":"41 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121059042","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Hybrid fs Dye/Excimer Lasers for Pump-Probe and High-Intensity Experiments","authors":"F. Schäfer, S. Szatmári, P. Simon","doi":"10.1364/up.1992.mb1","DOIUrl":"https://doi.org/10.1364/up.1992.mb1","url":null,"abstract":"For many experiments in physics, chemistry, and biology one needs a femtosecond pump-probe spectrometer with a strong pump pulse, preferably in the ultraviolet, and a jitter-free synchronized probe pulse, tunable over a wavelength range from the near ultraviolet to the near infrared. Such a spectrometer is usually very complex consisting of several lasers, synchronization and other electronics and electro-optical instrumentation. By contrast, we have designed a relatively simple, reliable spectrometer using only a single laser for the generation of the pump and the probe pulses absolutely jitter-free and without any electronic or electro-optic instrumentation. The spectrometer is schematically shown in Fig. 1. It contains a commercial excimer laser with two discharge channels operated by one thyratron for stable synchronization of the two discharges. One channel is operated as a XeCl oscillator whose output pumps a series of dye lasers giving finally an output pulse of .5 ps duration at 497 nm with more than 100 μJ pulse energy. Part of the output pulse is frequency-doubled and sent into the second discharge channel which is filled with KrF mixture. After a triple pass in an off-axis arrangement the output energy is 20 mJ in less than .5 ps. Since the output pulse has a strong positive chirp it can be compressed to less than 100 fs. The rest of the green pulse passes a two-grating compressor and is focussed into a 5 mm thick piece of quartz glass to produce a continuum. The collimated white light is sent through a dye amplifier cell pumped by the rest of the XeCl laser pulse energy through a delaying quartz fiber. After a second pass through the dye amplifier cell, the pulse is compressed in a pulse compressor consisting of two LiF prisms and a retroreflector to give a probe pulse output of less than 30 fs duration and 1 μJ energy. An aperture allows fine tuning the spectral position and width to give transform-limited pulses in a well collimated probe beam. With 7 different dyes one can cover the spectral region from 420 to 650 nm. In a similar scheme we have also used other excimers in order to reach different ultraviolet wavelengths.","PeriodicalId":242710,"journal":{"name":"Eighth International Conference on Ultrafast Phenomena","volume":"14 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121281891","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Stimulated Emission Pumping and Selective Excitation by Adiabatic Passage with Frequency Modulated Picosecond Laser Pulses","authors":"J. Melinger, A. Hariharan, S. R. Gandhi, W. Warren","doi":"10.1007/978-3-642-84910-7_29","DOIUrl":"https://doi.org/10.1007/978-3-642-84910-7_29","url":null,"abstract":"","PeriodicalId":242710,"journal":{"name":"Eighth International Conference on Ultrafast Phenomena","volume":"9 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132527271","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Ultrafast Formation Processes of Self-trapped Excitons in Alkali-iodide Crystals under Band-to-band Excitation","authors":"T. Tokizaki, S. Iwai, T. Shibata, A. Nakamura, K. Tanimura, N. Itoh","doi":"10.1007/978-3-642-84910-7_111","DOIUrl":"https://doi.org/10.1007/978-3-642-84910-7_111","url":null,"abstract":"","PeriodicalId":242710,"journal":{"name":"Eighth International Conference on Ultrafast Phenomena","volume":"23 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132316272","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Intense Laser Pulse Propagation and Wakefield Generation in Plasma","authors":"E. Esarey, P. Sprangle, J. Krall, G. Joyce","doi":"10.1364/up.1992.tua4","DOIUrl":"https://doi.org/10.1364/up.1992.tua4","url":null,"abstract":"Advances in laser technology have made possible compact terawatt laser systems with high intensities (I\u0000 0\u0000 ≥ 1018 W/cm2), modest energies (≤ 100 J) and short pulses (τl ≤ 1 ps). At ultra-high intensities, the laser-electron interaction becomes highly nonlinear and relativistic, thus resulting in a wide variety of new and interesting phenomena [1-5]. These phenomena include: (i) laser excitation of large amplitude plasma waves (wakefields) [1,3-5], (ii) relativistic optical guiding of laser pulses by plasmas [2-5], and (iii) optical guiding by preformed plasma channels [5]. This paper briefly discusses the these phenomena, including self-consistent, 2D-axisymmetric simulations.","PeriodicalId":242710,"journal":{"name":"Eighth International Conference on Ultrafast Phenomena","volume":"40 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128618381","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The C850X Ultrafast Streak Camera : An Instrument to Study Spatially and Temporally Subpicosecond Laser-Matter Interaction","authors":"A. Mens, R. Sauneuf, D. Schirmann, R. Verrecchia, P. Audebert, J. Gauthier, J. Geindre, A. Antonetti, J. Chambaret, G. Hamoniaux, A. Mysyrowicz","doi":"10.1007/978-3-642-84910-7_40","DOIUrl":"https://doi.org/10.1007/978-3-642-84910-7_40","url":null,"abstract":"","PeriodicalId":242710,"journal":{"name":"Eighth International Conference on Ultrafast Phenomena","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131280093","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Investigation of Femtosecond Pulse Induced Phase Transitions in GaAs","authors":"T. Schröder, P. Heist, S. Govorkov, I. Shumay, W. Rudolph","doi":"10.1364/up.1992.tuc23","DOIUrl":"https://doi.org/10.1364/up.1992.tuc23","url":null,"abstract":"There has been a great deal of interest in the investigation of the primary steps of phase transitions at semiconductor surfaces excited by an ultrashort laser pulse. Raman experiments [1] revealed that energy from the electronic system is transferred to the phonon system (lattice) on a time scale of about 1-2ps. Direct observation of the sample surface after excitation showed the onset of melting to be within a few or less than 1ps [2]. Second harmonic generation in reflection turned out to be a powerful tool to detect symmetry changes of the sample surface [3-5]. The general observation is that the drop of the second harmonic efficiency occurs within the first one hundred fs after excitation. In contrast the reflectivity of the fundamental changes on a time scale of several hundred fs up to one ps depending on the excitation density. While the SHG probes only about a layer of lOnm the reflectivity of the fundamental is determined by a layer thickness of several hundred nm. Therefore one possible explanation for the different time constants rests on propagation effects of the melt front, another assumes an intermediate state reflecting a changed lattice symmetry which is reached before a considerable part of energy is transferred to the phonon system (cold melting) [3]. We supplemented pump-probe and time resolved SHG in reflection by transient grating measurements. The latter are extremly sensitive against propagation effects because they change the grating structure and thus the diffraction efficiency. Corresponding measurements are shown in Fig.l. It is intresting to note that observable first-order diffraction occured only at excitation densities above the melting threshold. From Fig.1 it is evident that the diffraction dynamics is similar to that of the fundamental reflection. A theoretical model explains this as a consequence of the fact that propagation effects can be neglected within the first few ps. An upper limit for the velocity of the melt front velocity can be estimated and is in the order of 500 m/s. Since the diffraction rise time of the UV-probe (310nm) is considerably longer than the decay of the second harmonic efficiency the existence of an intermediate state or phase prior the melting becomes even more likely.","PeriodicalId":242710,"journal":{"name":"Eighth International Conference on Ultrafast Phenomena","volume":"76 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1900-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127358559","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}