Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Ultra-Broadband Visible and Infrared Light Generation Driven by Far
  Infrared Light in the Broad Region from 8{\mu}m to 240{\mu}m   The most commonly used nonlinear optical process is the conversion of
infrared light at 1064nm to green light at 532nm, as performed in common laser
pointers. However, more relevant for future applications are nonlinear optical
processes that generate a broad spectrum, a so called supercontinuum. A
desirable goal is generating a spectrum that covers the whole visible range
(400 -900nm), i.e., white light. Nowadays, white-light generation is usually
achieved in specially designed photonic fibres requiring high laser
intensities. However, in previous studies we showed that amorphous powders of
$(PhSn)_4S_6$ cluster-molecules generate white light when they are irradiated
by low-intensity near-infrared light. In this study, we use the mid- and
far-infrared radiation of a free-electron laser to investigate the same
molecules. White-light generation is observed for excitation with wavelength
between 8 and 240$\mu$ m. While the emitted radiation shows only slight
variations, its intensity strongly depends on the excitation wavelength. We
then match the wavelength dependent efficiency with the infrared absorption
spectra of the material. This comparison shows: whenever the excitation can
introduce molecular vibrations, less white light is generated. For all other
wavelengths the excitation interacts mostly with the electron system. This
shows that the electron system and the molecular backbone are decoupled to a
large extent. Our work contributes to the understanding of the nonlinear
process that underlies white-light generation in $(PhSn)_4S_6$ cluster
molecules. Additionally, it shows the high potential of this material in
applications where a broad laser spectrum is desired.

16
The categories of this paper are: stat
1
The categories of this paper are: cs
36
The categories of this paper are: cmp-lg
31
The categories of this paper are: ao-sci
26
The categories of this paper are: bayes-an
13
The categories of this paper are: quant-ph
27
The categories of this paper are: comp-gas
23
The categories of this paper are: solv-int
37
The categories of this paper are: supr-con
15
The categories of this paper are: nucl-ex
12
The categories of this paper are: nucl-th
22
The categories of this paper are: chao-dyn
25
The categories of this paper are: patt-sol
34
The categories of this paper are: chem-ph
24
The categories of this paper are: dg-ga
8
The categories of this paper are: hep-ex