226 research outputs found
Quantum beats in the polarization response of a dielectric to intense few-cycle laser pulses
We have investigated the polarization response of a dielectric to intense
few-cycle laser pulses with a focus on interband tunnelling. Once charge
carriers are created in an initially empty conduction band, they make a
significant contribution to the polarization response. In particular, the
coherent superposition of conduction- and valence-band states results in
quantum beats. This quantum-beat part of the polarization response is affected
by the excitation dynamics and attosecond-scale motion of charge carriers in an
intense laser field. Our analysis shows that, with the onset of Bloch
oscillations or tunnelling, the nonlinear polarization response becomes
sensitive to the carrier-envelope phase of the laser pulse.Comment: 10 pages, 5 figure
Strong-field Phenomena in Periodic Systems
The advent of visible-infrared laser pulses carrying a substantial fraction
of their energy in a single field oscillation cycle has opened a new era in the
experimental investigation of ultrafast processes in semiconductors and
dielectrics (bulk as well as nanostructured), motivated by the quest for the
ultimate frontiers of electron-based signal metrology and processing. Exploring
ways to approach those frontiers requires insight into the physics underlying
the interaction of strong high-frequency (optical) fields with electrons moving
in periodic potentials. This Colloquium aims at providing this insight.
Introduction to the foundations of strong-field phenomena defines and compares
regimes of field--matter interaction in periodic systems, including (perfect)
crystals as well as optical and semiconductor superlattices, followed by a
review of recent experimental advances in the study of strong-field dynamics in
crystals and nanostructures. Avenues toward measuring and controlling
electronic processes up to petahertz frequencies are discussed
Laserwire at the Accelerator Test Facility 2 with Sub-Micrometre Resolution
A laserwire transverse electron beam size measurement system has been
developed and operated at the Accelerator Test Facility 2 (ATF2) at KEK.
Special electron beam optics were developed to create an approximately 1 x 100
{\mu}m (vertical x horizontal) electron beam at the laserwire location, which
was profiled using a 150 mJ, 71 ps laser pulse with a wavelength of 532 nm. The
precise characterisation of the laser propagation allows the non-Gaussian
transverse profiles of the electron beam caused by the laser divergence to be
deconvolved. A minimum vertical electron beam size of 1.07 0.06 (stat.)
0.05 (sys.) {\mu}m was measured. A vertically focussing quadrupole just
before the laserwire was varied whilst making laserwire measurements and the
projected vertical emittance was measured to be 82.56 3.04 pm rad.Comment: 17 pages, 26 figures, submitted to Phys. Rev. ST Accel. Beam
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