Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Terahertz waves generation using the isomorphs of PPKTP crystal: a
  theoretical investigation   Highly efficient terahertz (THz) wave sources based on difference frequency
generation (DFG) process in nonlinear optical crystals play an important role
for the applications of THz wave. In order to find more novel nonlinear
crystals, here we theoretically investigate the generation of THz wave using
the isomorphs of periodically poled $\mathrm{KTiOPO_4}$ (PPKTP), including
periodically poled RTP, KTA, RTA and CTA. By solving the cascaded difference
frequency coupled wave equations, it is found that the intensities of the THz
wave generated from the cascaded difference frequency processes are improved by
5.27, 2.87, 2.82, 3.03, and 2.76 times from the non-cascaded cases for KTP,
RTP, KTA, RTA and CTA, respectively. The effects of the crystal absorption, the
phase mismatch and the pump intensity are also analyzed in detail. This study
might help to provide a stronger THz radiation source based on the nonlinear
crystals.

11
The categories of this paper are: hep-lat
25
The categories of this paper are: patt-sol
14
The categories of this paper are: math-ph
31
The categories of this paper are: ao-sci
9
The categories of this paper are: nlin
17
The categories of this paper are: q-fin
18
The categories of this paper are: econ
10
The categories of this paper are: q-bio
4
The categories of this paper are: cond-mat
22
The categories of this paper are: chao-dyn
6
The categories of this paper are: astro-ph
0
The categories of this paper are: hep-ph
32
The categories of this paper are: atom-ph
20
The categories of this paper are: acc-phys
21
The categories of this paper are: adap-org
27
The categories of this paper are: comp-gas