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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.


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Journal ArticleDOI
TL;DR: In this paper, a direct, point-by-point inscription of fibre Bragg gratings by infrared femtosecond laser is reported for the first time, in a non-photosensitised, standard telecommunication fibre and dispersion shifted fibre.
Abstract: Direct, point-by-point inscription of fibre Bragg gratings by infrared femtosecond laser is reported for the first time. Gratings of first to third order have been produced in non-photosensitised, standard telecommunication fibre and dispersion shifted fibre.

419 citations

Journal ArticleDOI
TL;DR: The conical emission is attributed to Cerenkov radiation from a dynamic self-guiding structure consisting of a weakly ionized core surrounded by Kerr cladding.
Abstract: Conical emission in the forward direction is observed from intense femtosecond light pulses propagating through air over long distances. The conical emission is attributed to Cerenkov radiation from a dynamic self-guiding structure consisting of a weakly ionized core surrounded by Kerr cladding.

417 citations

Journal ArticleDOI
16 Mar 1990-Science
TL;DR: Optical control over elementary molecular motion is enhanced with timed sequences of femtosecond pulses produced by pulse-shaping techniques, analogous to repetitively pushing a child on a swing with appropriate timing to build up a large oscillation amplitude.
Abstract: Optical control over elementary molecular motion is enhanced with timed sequences of femtosecond (10-15 second) pulses produced by pulse-shaping techniques. Appropriately timed pulse sequences are used to repetitively drive selected vibrations of a crystal lattice, in a manner analogous to repetitively pushing a child on a swing with appropriate timing to build up a large oscillation amplitude. This process corresponds to repetitively "pushing" molecules along selected paths in the lattice. Amplification of selected vibrational modes and discrimination against other modes are demonstrated. Prospects for more extensive manipulation of molecular and collective behavior and structure are clearly indicated.

417 citations

Journal ArticleDOI
02 Feb 2012-Nature
TL;DR: The generation of extreme-ultraviolet frequency combs, reaching wavelengths of 40 nanometres, is reported by coupling a high-power near-infrared frequency comb to a robust femtosecond enhancement cavity, and the absolute frequency of the argon transition has been determined by direct frequency comb spectroscopy.
Abstract: By coupling a high-power, high-repetition-rate near-infrared frequency comb to a femtosecond optical cavity, a frequency comb operating in the extreme-ultraviolet spectral range has been produced, by high harmonic generation, and provides high-resolution spectroscopy in this spectral region. Laser-based optical frequency combs, so called because they emit evenly spaced spectral lines, are used in precision spectroscopy and other applications requiring accurate measurements, such as atomic clocks. Efforts to extend this capability to shorter wavelengths in the extreme ultraviolet — which would open up exciting new applications, including searches for variation in fundamental constants — have lacked sufficient power for the purpose until now. Jun Ye and co-workers demonstrate a new approach, using a high-power, high-repetition pulsed infrared laser coupled into an optical cavity, to produce an improved extreme UV comb. In a first precision spectroscopy demonstration, they use direct frequency comb spectroscopy to determine argon and neon atomic transitions with ultra-high precision. The development of the optical frequency comb (a spectrum consisting of a series of evenly spaced lines) has revolutionized metrology and precision spectroscopy owing to its ability to provide a precise and direct link between microwave and optical frequencies1,2. A further advance in frequency comb technology is the generation of frequency combs in the extreme-ultraviolet spectral range by means of high-harmonic generation in a femtosecond enhancement cavity3,4. Until now, combs produced by this method have lacked sufficient power for applications, a drawback that has also hampered efforts to observe phase coherence of the high-repetition-rate pulse train produced by high-harmonic generation, which is an extremely nonlinear process. Here we report the generation of extreme-ultraviolet frequency combs, reaching wavelengths of 40 nanometres, by coupling a high-power near-infrared frequency comb5 to a robust femtosecond enhancement cavity. These combs are powerful enough for us to observe single-photon spectroscopy signals for both an argon transition at 82 nanometres and a neon transition at 63 nanometres, thus confirming the combs’ coherence in the extreme ultraviolet. The absolute frequency of the argon transition has been determined by direct frequency comb spectroscopy. The resolved ten-megahertz linewidth of the transition, which is limited by the temperature of the argon atoms, is unprecedented in this spectral region and places a stringent upper limit on the linewidth of individual comb teeth. Owing to the lack of continuous-wave lasers, extreme-ultraviolet frequency combs are at present the only promising route to extending ultrahigh-precision spectroscopy to the spectral region below 100 nanometres. At such wavelengths there is a wide range of applications, including the spectroscopy of electronic transitions in molecules6, experimental tests of bound-state and many-body quantum electrodynamics in singly ionized helium and neutral helium7,8,9, the development of next-generation ‘nuclear’ clocks10,11,12 and searches for variation of fundamental constants13 using the enhanced sensitivity of highly charged ions14.

417 citations

Journal ArticleDOI
TL;DR: In this paper, the authors review the generation of broadband THz radiation from femtosecond photo-induced gas plasmas, with an emphasis on the highly efficient AC-bias case where the plasma is generated and driven by a superposition of fundamental and second-harmonic optical fields.
Abstract: We review the generation of broadband THz radiation from femtosecond photo-induced gas plasmas, with an emphasis on the highly efficient "AC-bias" case where the plasma is generated and driven by a superposition of fundamental and second-harmonic optical fields. The dependence on experimental parameters such as pulse energy, air pressure, polarization and focusing are presented, and compared to the predictions from semi-quantitative models for the THz generation process, namely (i) a microscopic photocurrent model and (ii) a four. wave mixing model. We also employ these models to the case of few-cycle pulses, where the observed THz emission is related directly to the carrier-envelope phase of the pulses, and hence provides a mechanism with which to measure this phase.

416 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