Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Terahertz Strong-Field Physics in Light-Emitting Diodes for Terahertz
  Detection and Imaging   Intense terahertz (THz) electromagnetic fields have been utilized to reveal a
variety of extremely nonlinear optical effects in many materials through
nonperturbative driving of elementary and collective excitations. However, such
nonlinear photoresponses have not yet been discovered in light-emitting diodes
(LEDs), letting alone employing them as fast, cost effective,compact, and
room-temperature-operating THz detectors and cameras. Here we report
ubiquitously available LEDs exhibited gigantic and fast photovoltaic signals
with excellent signal-to-noise ratios when being illuminated by THz field
strengths >50 kV/cm. We also successfully demonstrated THz-LED detectors and
camera prototypes. These unorthodox THz detectors exhibited high responsivities
(>1 kV/W) with response time shorter than those of pyroelectric detectors by
four orders of magnitude. The detection mechanism was attributed to
THz-field-induced nonlinear impact ionization and Schottky contact. These
findings not only help deepen our understanding of strong THz field-matter
interactions but also greatly contribute to the applications of strong-field
THz diagnosis.

7
The categories of this paper are: hep-th
1
The categories of this paper are: cs
6
The categories of this paper are: astro-ph
19
The categories of this paper are: eess
24
The categories of this paper are: dg-ga
0
The categories of this paper are: hep-ph
10
The categories of this paper are: q-bio
29
The categories of this paper are: funct-an
27
The categories of this paper are: comp-gas
21
The categories of this paper are: adap-org
12
The categories of this paper are: nucl-th
33
The categories of this paper are: plasm-ph
23
The categories of this paper are: solv-int
17
The categories of this paper are: q-fin
2
The categories of this paper are: math
32
The categories of this paper are: atom-ph