Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Interband impact ionization and nonlinear absorption of terahertz
  radiations in semiconductor heterostructures   We have theoretically investigated nonlinear free-carrier absorption of
terahertz radiation in InAs/AlSb heterojunctions. By considering multiple
photon process and conduction-valence interband impact ionization (II), we have
determined the field and frequency dependent absorption rate. It is shown that
(i) electron-disorder scatterings are important at low to intermediate field,
and (ii) most importantly, the high field absorption is dominated by II
processes. Our theory can satisfactorily explain a long standing experimental
result on the nonlinear absorption in THz regime.

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
32
The categories of this paper are: atom-ph
28
The categories of this paper are: alg-geom
2
The categories of this paper are: math
21
The categories of this paper are: adap-org
25
The categories of this paper are: patt-sol
24
The categories of this paper are: dg-ga
3
The categories of this paper are: physics
18
The categories of this paper are: econ
5
The categories of this paper are: gr-qc
14
The categories of this paper are: math-ph
10
The categories of this paper are: q-bio
29
The categories of this paper are: funct-an
19
The categories of this paper are: eess