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Femtosecond

About: Femtosecond is a research topic. Over the lifetime, 35106 publications have been published within this topic receiving 691405 citations. The topic is also known as: 1 E-15 s & fs.


Papers
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Journal ArticleDOI
TL;DR: The dependence of the stimulated Raman signal on experimental parameters is explored, demonstrating the expected exponential increase in Raman intensity with concentration, pathlength, and Raman pump power.
Abstract: The laser, detection system, and methods that enable femtosecond broadband stimulated Raman spectroscopy (FSRS) are presented in detail. FSRS is a unique tool for obtaining high time resolution (<100 fs) vibrational spectra with an instrument response limited frequency resolution of <10 cm(-1). A titanium:Sapphire-based laser system produces the three different pulses needed for FSRS: (1) A femtosecond visible actinic pump that initiates the photochemistry, (2) a narrow bandwidth picosecond Raman pump that provides the energy reservoir for amplification of the probe, and (3) a femtosecond continuum probe that is amplified at Raman resonances shifted from the Raman pump. The dependence of the stimulated Raman signal on experimental parameters is explored, demonstrating the expected exponential increase in Raman intensity with concentration, pathlength, and Raman pump power. Raman spectra collected under different electronic resonance conditions using highly fluorescent samples highlight the fluorescence rejection capabilities of FSRS. Data are also presented illustrating our ability: (i) To obtain spectra when there is a large transient absorption change by using a shifted excitation difference technique and (ii) to obtain high time resolution vibrational spectra of transient electronic states.

287 citations

Journal ArticleDOI
TL;DR: An embedded fiber-taper saturable absorber is proposed and demonstrated based on a fiber taper embedded in a carbon nanotube/polymer composite and an all-fiber mode-locked ring laser is built.
Abstract: We propose and demonstrate a new saturable absorber based on a fiber taper embedded in a carbon nanotube/polymer composite. Greater than a 10% reduction in absorption (due to saturation) is directly measured for our saturable absorber. Using an embedded fiber-taper saturable absorber, we built an all-fiber mode-locked ring laser, which produces 594 fs/1.7 nJ pulses with a repetition rate of 13.3 MHz.

286 citations

Journal ArticleDOI
TL;DR: A novel method to generate femTosecond and subfemtosecond photon pulses in a free-electron laser by selectively spoiling the transverse emittance of the electron beam, which can provide x-ray pulses the order of 1 fs in duration containing about 10 transversely coherent photons.
Abstract: We propose a novel method to generate femtosecond and subfemtosecond photon pulses in a free-electron laser by selectively spoiling the transverse emittance of the electron beam. Its merits are simplicity and ease of implementation. When the system is applied to the Linac Coherent Light Source, it can provide x-ray pulses the order of 1 fs in duration containing about 10(10) transversely coherent photons.

286 citations

Journal ArticleDOI
TL;DR: A new technique, femtosecond transillumination optical coherence tomography, for time-gated imaging of objects embedded in scattering media, derives a fundamental limit on ballistic imaging thickness based on quantum noise considerations.
Abstract: We describe a new technique, femtosecond transillumination optical coherence tomography, for time-gated imaging of objects embedded in scattering media. Time gating is performed with a fiber-optic interferometer with femtosecond pulses and coherent heterodyne detection to achieve a 130-dB dynamic range. A confocal imaging arrangement provides additional spatial discrimination against multiply scattered light. By time gating ballistic photons, we achieve 125-microm-resolution images of absorbing objects in media 27 scattering mean free paths thick. We derive a fundamental limit on ballistic imaging thickness based on quantum noise considerations.

286 citations

Journal ArticleDOI
TL;DR: In this paper, the interaction of ultrashort laser pulses with materials involves a number of special features that are different from laser-matter interaction for longer pulse durations, and the fundamental physical processes such as energy deposition, melting and ablation are separated in time.
Abstract: The interaction of ultrashort laser pulses with materials involves a number of special features that are different from laser–matter interaction for longer pulse durations. For femtosecond laser excitation the fundamental physical processes such as energy deposition, melting, and ablation are separated in time. By choosing proper time windows, the various processes can be investigated separately. We present selected examples of theoretical studies of free electron excitation in metals, timescales of different melting processes, and peculiarities of near-threshold ablation. Depending on the timescales and intensity ranges, the discussed processes are combined in an overall picture of possible pathways of the material from excitation to ablation.

285 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
20231,403
20223,116
20211,239
20201,571
20191,715
20181,651