Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Directional terahertz emission from diffusion-engineered InAs structures   We have designed and fabricated a new type of terahertz (THz) emitter that
radiates THz waves along the surface-normal direction because of the lateral
distributions of the transient electric dipoles. The excitation and
measurements were performed using a conventional THz time-domain spectroscopy
scheme with femtosecond optical pulses. The corrugated mirror patterns on the
InAs layers made the radiation directional along the surface-normal direction,
and the emission efficiency was controlled by adjustment of the pattern width.

14
The categories of this paper are: math-ph
25
The categories of this paper are: patt-sol
15
The categories of this paper are: nucl-ex
13
The categories of this paper are: quant-ph
12
The categories of this paper are: nucl-th
33
The categories of this paper are: plasm-ph
20
The categories of this paper are: acc-phys
34
The categories of this paper are: chem-ph
2
The categories of this paper are: math
26
The categories of this paper are: bayes-an
36
The categories of this paper are: cmp-lg
18
The categories of this paper are: econ
35
The categories of this paper are: mtrl-th
0
The categories of this paper are: hep-ph
27
The categories of this paper are: comp-gas
23
The categories of this paper are: solv-int