Make the measurement of as pulses difficult!
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(III-1) Measurement of as pulse trains
(1) RABITT (Reconstruction of Attosecond harmonic Beating by Interference of Two-photon Transitions) (2) Intensity autocorrelation (3) SPIDER (Spectral Phase Interferometry for Direct Electronic field Reconstruction ) (as pulse trains & single as pulses)
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Single as pulses
(1’)The ‘‘atomic Pockels cell’’ generation
(Polarization gating)
E E0 f (t)cos(1t)x cos(2t)y
2
E E0 f (t) cos(t) cos(t / 2)x' sin(t) sin(t / 2)y'
3
(I) Introduction
Processes and intervals on different time scales.
4
1 attosecond ~ 10-18 s Characteristic timescale: 150as (Hydrogen atom, Bohr’s Model)
Coherently superposing a broad band of harmonic from the plateau region where all harmonics have nearly equal amplitudes.
9
Production of as pulse trains
nc
E(t) En cos(n0t) nnp
2
nc
E
2
(t
)
En
c
os(n0t
)
nnp
N– number of odd harmonics of the plateau (N=np-nc) np, nc– the first and last component of the plateau
radiation including a broad continuum) emitted only at the peak of the femtosecond laser pulse (5’) Multifrequency Cascaded Stimulated Raman Scattering (CSRS) (as pulse trains & single as pulses)
(as pulse trains & single as pulses)
8
Production of
(1) Fourier synthesis of laser induced multipleas pulse trains harmonics
~ 1/ ~ 1/(2N) ~ 30as
~ 1.81015 s1
(1exp[(t / T )2 ]
T=10 periods of the fundamental
time-dependent ellipticity f(t) describes an ultrashort pulse
t 0, n Linear polarized
-e +
5
2007-10-24
6
Outline
(I) Introduction (II) Generation (III) Detection (IV) Applications
7
(II-1) Production of as pulse trains
(1) Fourier synthesis of laser induced multiple harmonics
Attosecond Pulses: Generation, Detection and Applications
1
Outline
(I) Introduction (II) Generation (III) Detection (IV) Applications
2
Outline
(I) Introduction (II) Generation (III) Detection (IV) Applications
(1) Fourier synthesis of laser induced multiple harmonics (continued)
Experimental scheme
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(II-2) A single attosecond pulse generation
(1’) The ‘‘atomic Pockels cell’’ (Polarization gating) (2’) High harmonic generation with few cycle laser pulses (3’) From a multi-cycle two-color laser (4’) Selecting the harmonic radiation (implying all the
(2) Harmonic emission, within a laser oscillation period, confined to a small fraction of To/2 (within a limited frequency band near the cutoff)
(3) Multifrequency Cascaded Stimulated Raman Scattering (CSRS)
12
Outline
(I) Introduction (II) Generation (III) Detection (IV) Applications
13
(III) Detection
Short wavelength Low intensity Short duration
Spatiotemporal shape of an as pulse (r is the transverse coordinate)