Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Study of the spatial and temporal coherence of high order harmonics   We apply the theory of high-order harmonic generation by low-frequency laser
fields in the strong field approximation to the study of the spatial and
temporal coherence properties of the harmonics. We discuss the role of
dynamically induced phases of the atomic polarization in determining the
optimal phase matching conditions and angular distributions of harmonics. We
demonstrate that the phase matching and the spatial coherence can be controlled
by changing the focusing parameters of the fundamental laser beam. Then we
present a detailed study of the temporal and spectral properties of harmonics.
We discuss how the focusing conditions influence the individual harmonic
spectra and time profiles, and how the intensity dependence of the dynamically
induced phase leads to a chirp of the harmonic frequency. This phase modulation
can be used to control the temporal and spectral properties of the harmonic
radiation. Temporally, the harmonic chirped pulse can be recompressed to very
small durations. Spectrally, chirping of the fundamental beam may be employed
to compensate for the dynamically induced chirp and to control the individual
harmonic spectrum. Finally, we discuss the short pulse effects, in particular
nonadiabatic phenomena and the possibility of generating attosecond pulses.

11
The categories of this paper are: hep-lat
16
The categories of this paper are: stat
35
The categories of this paper are: mtrl-th
6
The categories of this paper are: astro-ph
26
The categories of this paper are: bayes-an
12
The categories of this paper are: nucl-th
17
The categories of this paper are: q-fin
4
The categories of this paper are: cond-mat
34
The categories of this paper are: chem-ph
15
The categories of this paper are: nucl-ex
23
The categories of this paper are: solv-int
33
The categories of this paper are: plasm-ph
2
The categories of this paper are: math
0
The categories of this paper are: hep-ph
3
The categories of this paper are: physics
19
The categories of this paper are: eess