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Femtosecond Laser Pulses (femtosecond + laser_pulse)
Selected AbstractsFluorescence Spectroscopy of Color Centers Generated in Phosphate Glasses after Exposure to Femtosecond Laser PulsesJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 5 2002James W. Chan A confocal fluorescence microscopy setup was used to observe, in situ, spectral changes in phosphate glasses which were modified using 0.3 ,J of tightly focused 800 nm, 130 fs laser pulses. On 488 nm excitation, the modified glass shows a broad fluorescence centered at roughly 600 nm, which decays with prolonged exposure to the 488 nm light. The decay behavior is dependent on the 488 nm power, with a faster decay rate for higher powers. A mechanism whereby color centers, formed by the femtosecond pulses, fluoresce when excited by the 488 nm light and are simultaneously photobleached is proposed to explain the observed behavior. [source] Computational modeling of supercontinuum generation in fused silica by a femtosecond laser pulse of a few optical cyclesMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 1 2004David Hovhannisyan Abstract The numerical solution of a wave equation describing the propagation of the laser pulse of a few optical cycles in fused silica is obtained. Our numerical simulations closely follow the published experimental data. A shifting of the spectrum peak of the broadened pulse, depending on the input-pulse central wavelength, is observed. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 42: 60,64, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20207 [source] Single-Photon and Two-Photon Induced Photocleavage for Monolayers of an Alkyltriethoxysilane with a Photoprotected Carboxylic Ester,ADVANCED MATERIALS, Issue 23 2008Marta Álvarez The photochemical structuring of a polysiloxane monolayer protected with a photocleavable group is shown by femtosecond laser pulses in the near infrared. These experiments suggest a two-photon induced deprotection process that holds great promise for near-field monolayer photolithography far below the diffraction limit. [source] Formation and reactions of cluster ions from aromatic carboxylic acids together with amino acidsISRAEL JOURNAL OF CHEMISTRY, Issue 2 2001Anja Meffert The cluster formation of several aromatic carboxylic acids, ferulic acid, vanillic acid, sinapinic acid, and 3,4-dihydroxybenzoic acid was investigated by means of laser desorption into a supersonic beam followed by multiphoton ionization-time-of-flight mass spectrometry. The formation of not only homogeneous clusters, but also of heterogeneous clusters with some small amino acids was studied. The different neutral clusters formed in the supersonic expansion were ionized by a multiphoton process employing either nano- or femtosecond laser pulses. Strong differences in the detection of cluster ions due to the laser pulse length employed for multiphoton ionization were observed. Only femtosecond activation led to mass spectra with intense signals of the cluster ions. In addition, in the case of femtosecond ionization, protonated amino acids were detected in the mass spectra. As direct ionization of the free amino acids is not possible under the chosen ionization conditions because they lack an adequate chromophore, these protonated amino acids are assumed to be formed via an intracluster proton transfer in the heterogeneous dimer and subsequent decay of the ionized cluster (dissociative proton transfer). Such well-known processes for heterogeneous clusters consisting of a substituted aromatic molecule and small polar solvent molecules may be involved in the matrixassisted laser desorption ionization (MALDI) process. [source] Optical knock out of stem cells with extremely ultrashort femtosecond laser pulsesJOURNAL OF BIOPHOTONICS, Issue 6 2008Aisada Uchugonova Abstract Novel ultracompact multiphoton sub-20 femtosecond near infrared 85 MHz laser scanning microscopes and conventional 250 fs laser microscopes have been used to perform high spatial resolution two-photon imaging of stem cell clusters as well as selective intracellular nanoprocessing and knock out of living single stem cells within an 3D microenvironment without any collateral damage. Also lethal cell exposure of large parts of cell clusters was successfully probed while maintaining single cells of interest alive. The mean power could be kept in the milliwatt range for 3D nanoprocessing and even in the microwatt range for two-photon imaging. Ultracompact low power sub-20 fs laser systems may become interesting tools for optical nanobiotechnology such as optical cleaning of stem cell clusters as well as optical transfection. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] In vitro femtosecond laser subsurface micro-disruption inside human cornea and pre-cleared scleraLASER PHYSICS LETTERS, Issue 6 2010A.A. Alekhin Abstract Micro-incisions were fabricated inside human cornea and sclera in vitro using single femtosecond laser pulses. In these experiments sclera was for the first time pre-cleared by means of a biocompatible and clinically safe (non-toxic) natural agent (refractive-index matching 40%-glucose solution in water), partially replacing water in the tissue comparing to its severe dehydration by previously used agents. Basic operational parameters of the corresponding microsurgical procedures are reported. (© 2010 by Astro Ltd., Published exclusively by WILEY-VCH Verlag GmbH & Co. KGaA) [source] Conversion of silver nanoprisms into colloidal nanoparticles induced by femtosecond laser pulsesLASER PHYSICS LETTERS, Issue 3 2004Qitao Zhao Abstract Shape transformation of silver nanoprisms in aqueous solution was studied using femtosecond laser pulses. Irradiation of a pulsed Ti:Sapphire laser at 800 nm caused the shape change of the nanoprisms from triangle into sphere, forming a stable colloid of a narrow size distribution with the particle diameters having ,10 nm. The effects of laser fluence on fragmentation and conversion were investigated using UV-vis absorption spectroscopy and transmission electron microscopy. The mechanism of laser-induced colloid formation is discussed. (© 2004 by HMS Consultants. Inc. Published exclusively by WILEY-VCH Verlag GmbH & Co.KGaA) [source] Femtosecond laser-assisted formation of channels in sapphire using KOH solutionPHYSICA STATUS SOLIDI - RAPID RESEARCH LETTERS, Issue 6 2008Saulius Juodkazis Abstract We report on wet etching of photomodified regions in crystalline sapphire using KOH solution. Tightly focused femtosecond laser pulses (150 fs at 800 nm wavelength) were used to create void structures enclosed in an amorphised sapphire shell inside the bulk of a crystalline host. The diameter of the amorphous regions can be controlled by pulse energy and was typically 0.5,1.5 µm. The etching rate depends on the distance between adjacent irradiation spots, pulse energy, concentration of etchant and ultrasonic agitation. Amorphised sapphire is etched out in KOH solution. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] A narrow band, green-red colour centre laser in LiF fabricated by femtosecond laser pulsesPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 3 2007T. Kurobori Abstract Recent advances in high-intensity femtosecond (fs) laser pulses have made it possible to encode non-erasable functional micro-structures inside almost any type of photo-insensitive transparent materials. We focus our attention on bulk lithium fluoride (LiF) because of its broad emission band from the green-to-red spectral range under excitation of a single absorption band at about 450 nm. Here a room temperature, visible laser action in LiF from a distributed-feedback laser with embedded fine-pitched gratings written by fs pulses and from a laser-active colour centre laser with multilayer dielectric mirrors has been demonstrated. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Fabrication of buried waveguides and nanocrystals in Er3+ -doped oxyfluoride glassPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 7 2005V. K. Tikhomirov Abstract We report on direct writing of three-dimensional structures within the bulk of the Er3+ -doped oxyfluoride precursor glass using tightly focused femtosecond Ti-sapphire laser pulses at 800 nm wavelength. Buried 1 µm diameter channel and spherical waveguides and three-dimensional periodic arrays of 1 µm diameter dots have been fabricated. In the latter case, the dot could be written with a single 25 fs laser pulse. When the laser pulse energy exceeded 10 µJ/pulse/µm2, the writing resulted in nano-ceraming of the precursor glass and creation of about 2 to 3 nm diameter Er3+ -doped fluoride nanocrystals within the written dots/waveguides, as confirmed by a characteristic change in shape of the 1.5 µm photoluminescence band of the Er3+ ions. The diameter of the buried dots/wave-guides, and the photoinduced change of their refractive index, can be varied by changing the number of femtosecond laser pulses, the beam waist diameter, and/or laser intensity. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Refractive index-modulated grating in two-mode planar polymeric waveguide produced by two-photon polymerizationPOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 7 2007Yi Dong Abstract A polymeric waveguide film was manufactured by spinning the materials on quartz substrate. Two-photon-initiated photopolymerization was carried out by tight-focusing femtosecond laser pulses in the two-mode planar waveguide. A typical index-modulated grating of 2.5,×,2,mm areas without morphology was fabricated. The results show that peak-to-peak modulation depth of the surface profile of grating region was only about 7,nm. The diffraction efficiency (DE) of the grating with a spacing period 2,µm was 0.17% and the corresponding index modulation reached 5.7,×,10,3. Copyright © 2007 John Wiley & Sons, Ltd. [source] | |||||||||||||