Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Extraction of higher-order nonlinear electronic response to strong field
  excitation in solids using high harmonic generation   State-of-the-art experiments employ strong ultrafast optical fields to study
the nonlinear response of electrons in solids on an attosecond time-scale.
Notably, a recent experiment retrieved a 3rd order nonlinear susceptibility by
comparing the nonlinear response induced by a strong laser field to a linear
response induced by the otherwise identical weak field. In parallel,
experiments have demonstrated high harmonic generation (HHG) in solids, a
highly nonlinear process that until recently had only been observed in gases.
The highly nonlinear nature of HHG has the potential to extract even higher
order nonlinear susceptibility terms, and thereby characterize the entire
response of the electronic system to strong field excitation. However, up till
now, such characterization has been elusive due to a lack of direct
correspondence between high harmonics and nonlinear susceptibilities. Here, we
demonstrate a regime where such correspondence can be clearly made, extracting
nonlinear susceptibilities (7th, 9th, and 11th) from sapphire of the same order
as the measured high harmonics. The extracted high order susceptibilities show
angular-resolved periodicities arising from variation in the band structure
with crystal orientation. Nonlinear susceptibilities are key to ultrafast
lightwave driven optoelectronics, allowing petahertz scaling manipulation of
the signal. Our results open a door to multi-channel signal processing,
controlled by laser polarization.

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The categories of this paper are: cond-mat
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The categories of this paper are: hep-ex
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The categories of this paper are: hep-lat
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The categories of this paper are: nlin
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The categories of this paper are: eess
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The categories of this paper are: acc-phys
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The categories of this paper are: patt-sol
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The categories of this paper are: bayes-an
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The categories of this paper are: q-fin
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The categories of this paper are: solv-int
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The categories of this paper are: funct-an
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The categories of this paper are: adap-org
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The categories of this paper are: econ
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The categories of this paper are: astro-ph
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The categories of this paper are: q-bio
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The categories of this paper are: q-alg