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Pulse duration

About: Pulse duration is a research topic. Over the lifetime, 19429 publications have been published within this topic receiving 286507 citations.


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Journal ArticleDOI
TL;DR: It is shown how the extra degrees of freedom (pump-pulse duration, intensity, frequency, and time delay), which are absent in a conventional steady-state experiment, provide additional information about electronic structure and dynamics that improve characterization of a system.
Abstract: Molecular absorption and photo-electron spectra can be efficiently predicted with real-time time-dependent density-functional theory (TDDFT). We show here how these techniques can be easily extended to study time-resolved pump-probe experiments in which a system response (absorption or electron emission) to a probe pulse, is measured in an excited state. This simulation tool helps to interpret the fast evolving attosecond time-resolved spectroscopic experiments, where the electronic motion must be followed at its natural time-scale. We show how the extra degrees of freedom (pump pulse duration, intensity, frequency, and time-delay), which are absent in a conventional steady state experiment, provide additional information about electronic structure and dynamics that improve a system characterization. As an extension of this approach, time-dependent 2D spectroscopies can also be simulated, in principle, for large-scale structures and extended systems.

92 citations

Patent
03 Dec 2002
TL;DR: In this article, a method for material modification using laser (302) bursts including appropriately timed laser pulses (702, 704) to enhance material (314, 366) modification is described.
Abstract: Methods and apparatus for material modification using laser (302) bursts including appropriately timed laser pulses (702, 704) to enhance material (314, 366) modification. In one implementation, a method for material modification comprises the steps of: providing bursts of laser pulses, wherein each burst comprises at least two laser pulses (702, 704), wherein each laser pulse has a pulse duration within a range of between approximately 10 ps and 100 ns, wherein a time between each laser pulse of each burst is within a range of between approximately 5 ns and 5 us; a time between successive bursts is greater than the time between each laser pulse comprising each burst; and directing the bursts upon a workpiece (314, 366), wherein an intensity of a primary laser pulse (702) of each burst exceeds a damage threshold (802) of the workpiece.

92 citations

Journal ArticleDOI
TL;DR: In this article, the impact of laser pulses with lengths ranging from 5 ps down to 10 fs on a target of approximately 100A x 100A × 50A was investigated, and the ablation shows a strong dependence on pulse length, on pulse energy and on the number of laser shots.
Abstract: Molecular Dynamics (MD) simulation has been employed in order to study laser ablation of silicon surfaces. The impact of laser pulses with lengths ranging from 5 ps down to 10 fs on a target of approximately 100A x 100A x 50A was investigated. The ablation shows a strong dependence on pulse length, on pulse energy and on the number of laser shots. With decreasing pulse length the amount of removed particles increases, and with decreasing pulse energy the holes become narrower. Especially in multishot ablations, holes with a diameter of just a fraction of the focus could be observed. This can be attributed mainly to ablation of atoms from lower areas and their redeposition close to the surface, leading to amorphous areas around the ablation hole. For pulses of picosecond duration, and even for femtosecond pulses, the main material removal occurs on a timescale of a few ps. Interestingly, the simulations show two thresholds: the onset of damage at the surface. which depends on the pulse energy but only insignificantly on the pulse length; and the onset of the removal of particles, which shows a strong dependence on the pulse length of the laser.

92 citations

Journal ArticleDOI
TL;DR: In this article, the Lamb9s problem is considered for a version of point force on the surface of a uniform half-space and the resulting surface disturbance is computed as vertical and horizontal components of displacement, particle velocity, acceleration, and strain.
Abstract: We consider a version of Lamb9s Problem in which a vertical time-dependent point force acts on the surface of a uniform half-space. The resulting surface disturbance is computed as vertical and horizontal components of displacement, particle velocity, acceleration, and strain. The goal is to provide numerical solutions appropriate to a comparison with observed wave forms produced by impacts onto granite and onto soil. Solutions for step- and delta-function sources are not physically realistic but represent limiting cases. They show a clear P arrival (larger on horizontal than vertical components) and an obscure S arrival. The Rayleigh pulse includes a singularity at the theoretical arrival time. All of the energy buildup appears on the vertical components and all of the energy decay , on the horizontal components. The effects of Poisson9s ratio upon vertical displacements for a step-function source are shown. For fixed shear velocity, an increase of Poisson9s ratio produces a P pulse which is larger, faster, and more gradually emergent, an S pulse with more clear-cut beginning, and a much narrower Rayleigh pulse. For a source-time function given by cos 2 ( πt / T ), − T /2 ≦ T /2, a × 10 reduction in pulse width at fixed pulse height yields an increase in P and Rayleigh-wave amplitudes by factors of 1, 10, and 100 for displacement, velocity and strain, and acceleration, respectively. The observed wave forms appear somewhat oscillatory, with widths proportional to the source pulse width. The Rayleigh pulse appears as emergent positive on vertical components and as sharp negative on horizontal components. We show a theoretical seismic profile for granite, with source pulse width of 10 µsec and detectors at 10, 20, 30, 40, and 50 cm. Pulse amplitude decays as r −1 for P wave and r − 1 2 for Rayleigh wave. Pulse width broadens slightly with distance but the wave form character remains essentially unchanged.

92 citations

Journal ArticleDOI
TL;DR: An efficient all-fiber saturable absorber (SA) that evanescently interacts with a graphene monolayer by employing an over-cladding structure on high-quality monolayers that uniformly covered the side-polished fiber is demonstrated.
Abstract: We demonstrate an efficient all-fiber saturable absorber (SA) that evanescently interacts with a graphene monolayer. Strong nonlinear interaction between the graphene sheet and evanescent wave was realized in both experiments and numerical calculations by employing an over-cladding structure on high-quality monolayer graphene that uniformly covered the side-polished fiber. A passively mode-locked Er-doped fiber laser was built, including our in-line graphene SA, which stably generated ultrashort pulses with pulse duration of 377 fs at a repetition rate of 37.7 MHz. The corresponding 3-dB spectral bandwidth of the laser was measured to be 8.6 nm at the central wavelength of 1607.7 nm. We also experimentally observed that the spectral bandwidth and pulse duration of the laser output could be controlled by proper selection of the refractive index of the over-cladding material on the monolayer-graphene SA.

92 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
2023175
2022408
2021543
2020619
2019668
2018665