Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Spectral dynamics of THz pulses generated by two-color laser filaments
  in air: The role of Kerr nonlinearities and pump wavelength   We theoretically and numerically study the influence of both instantaneous
and Raman-delayed Kerr nonlinearities as well as a long-wavelength pump in the
terahertz (THz) emissions produced by two-color femtosecond filaments in air.
Although the Raman-delayed nonlinearity induced by air molecules weakens THz
generation, four-wave mixing is found to impact the THz spectra accumulated
upon propagation via self-, cross-phase modulations and self-steepening.
Besides, using the local current theory, we show that the scaling of
laser-to-THz conversion efficiency with the fundamental laser wavelength
strongly depends on the relative phase between the two colors, the pulse
duration and shape, rendering a universal scaling law impossible. Scaling laws
in powers of the pump wavelength may only provide a rough estimate of the
increase in the THz yield. We confront these results with comprehensive
numerical simulations of strongly focused pulses and of filaments propagating
over meter-range distances.

18
The categories of this paper are: econ
20
The categories of this paper are: acc-phys
0
The categories of this paper are: hep-ph
19
The categories of this paper are: eess
28
The categories of this paper are: alg-geom
12
The categories of this paper are: nucl-th
26
The categories of this paper are: bayes-an
6
The categories of this paper are: astro-ph
29
The categories of this paper are: funct-an
13
The categories of this paper are: quant-ph
4
The categories of this paper are: cond-mat
27
The categories of this paper are: comp-gas
21
The categories of this paper are: adap-org
32
The categories of this paper are: atom-ph
37
The categories of this paper are: supr-con
10
The categories of this paper are: q-bio