<s>
A	O
terahertz	B-Algorithm
metamaterial	I-Algorithm
is	O
a	O
class	O
of	O
composite	O
metamaterials	O
designed	O
to	O
interact	O
at	O
terahertz	B-Architecture
(	O
THz	B-Architecture
)	O
frequencies	O
.	O
</s>
<s>
The	O
terahertz	B-Architecture
frequency	O
range	O
used	O
in	O
materials	O
research	O
is	O
usually	O
defined	O
as	O
0.1	O
to	O
10	O
THz	B-Architecture
.	O
</s>
<s>
This	O
bandwidth	B-Algorithm
is	O
also	O
known	O
as	O
the	O
terahertz	B-Architecture
gap	O
because	O
it	O
is	O
noticeably	O
underutilized	O
.	O
</s>
<s>
This	O
is	O
because	O
terahertz	B-Architecture
waves	I-Architecture
are	O
electromagnetic	O
waves	O
with	O
frequencies	O
higher	O
than	O
microwaves	O
but	O
lower	O
than	O
infrared	O
radiation	O
and	O
visible	O
light	O
.	O
</s>
<s>
These	O
characteristics	O
mean	O
that	O
it	O
is	O
difficult	O
to	O
influence	O
terahertz	B-Architecture
radiation	I-Architecture
with	O
conventional	O
electronic	O
components	O
and	O
devices	O
.	O
</s>
<s>
Likewise	O
,	O
the	O
terahertz	B-Architecture
gap	O
also	O
borders	O
optical	B-Algorithm
or	O
photonic	B-Application
wavelengths	I-Application
;	O
the	O
infrared	O
,	O
visible	O
,	O
and	O
ultraviolet	B-Application
ranges	O
(	O
or	O
spectrums	O
)	O
,	O
where	O
well	O
developed	O
lens	O
technologies	O
also	O
exist	O
.	O
</s>
<s>
However	O
,	O
the	O
terahertz	B-Architecture
wavelength	O
,	O
or	O
frequency	O
range	O
,	O
appears	O
to	O
be	O
useful	O
for	O
security	O
screening	O
,	O
medical	B-Application
imaging	I-Application
,	O
wireless	O
communications	O
systems	O
,	O
non-destructive	O
evaluation	O
,	O
and	O
chemical	O
identification	O
,	O
as	O
well	O
as	O
submillimeter	O
astronomy	O
.	O
</s>
<s>
Finally	O
,	O
as	O
a	O
non-ionizing	O
radiation	O
it	O
does	O
not	O
have	O
the	O
risks	O
inherent	O
in	O
X-ray	B-Library
screening	I-Library
.	O
</s>
<s>
Yet	O
,	O
the	O
interaction	O
achieved	O
is	O
below	O
the	O
dimensions	O
of	O
the	O
terahertz	B-Architecture
radiation	I-Architecture
wave	O
.	O
</s>
<s>
This	O
results	O
in	O
common	O
optical	B-Algorithm
limitations	O
such	O
as	O
a	O
diffraction	O
barrier	O
.	O
</s>
<s>
Terahertz	B-Architecture
frequencies	O
,	O
or	O
submillimeter	O
wavelengths	O
,	O
which	O
exist	O
between	O
microwave	O
frequencies	O
and	O
infrared	O
wavelengths	O
can	O
be	O
metaphorically	O
termed	O
"	O
unclaimed	O
territory	O
"	O
where	O
almost	O
no	O
devices	O
exist	O
.	O
</s>
<s>
Because	O
there	O
are	O
limits	O
to	O
propagating	O
the	O
terahertz	B-Architecture
band	I-Architecture
through	O
the	O
atmosphere	O
,	O
the	O
commercial	O
sector	O
has	O
remained	O
uninvolved	O
with	O
such	O
technological	O
development	O
.	O
</s>
<s>
However	O
,	O
terahertz	B-Architecture
devices	O
have	O
been	O
useful	O
in	O
the	O
remote	B-Application
sensing	I-Application
and	O
spectroscopy	O
areas	O
.	O
</s>
<s>
Indeed	O
,	O
the	O
cosmos	O
is	O
suffused	O
in	O
terahertz	B-Architecture
energy	O
,	O
and	O
meanwhile	O
,	O
almost	O
all	O
of	O
it	O
appears	O
to	O
be	O
overlooked	O
,	O
disregarded	O
,	O
or	O
simply	O
unidentified	O
.	O
</s>
<s>
Development	O
of	O
metamaterials	O
has	O
traversed	O
the	O
electromagnetic	O
spectrum	O
up	O
to	O
terahertz	B-Architecture
and	O
infrared	O
frequencies	O
,	O
but	O
does	O
not	O
yet	O
include	O
the	O
visible	O
light	O
spectrum	O
.	O
</s>
<s>
The	O
fundamental	O
elements	O
for	O
terahertz	B-Architecture
and	O
infrared	O
frequencies	O
have	O
been	O
progressively	O
scaled	O
to	O
smaller	O
sizes	O
.	O
</s>
<s>
Along	O
with	O
the	O
ability	O
to	O
now	O
interact	O
at	O
terahertz	B-Architecture
frequencies	O
is	O
the	O
desire	O
to	O
build	O
,	O
deploy	O
,	O
and	O
integrate	O
THz	B-Architecture
metamaterial	O
applications	O
universally	O
into	O
society	O
.	O
</s>
<s>
This	O
is	O
because	O
,	O
as	O
explained	O
above	O
,	O
components	O
and	O
systems	O
with	O
terahertz	B-Architecture
capabilities	O
will	O
fill	O
a	O
technologically	O
relevant	O
void	O
.	O
</s>
<s>
Research	O
has	O
begun	O
with	O
first	O
,	O
demonstrating	O
the	O
practical	O
terahertz	B-Algorithm
metamaterial	I-Algorithm
.	O
</s>
<s>
Moreover	O
,	O
since	O
,	O
many	O
materials	O
do	O
not	O
respond	O
to	O
THz	B-Architecture
radiation	I-Architecture
naturally	O
,	O
it	O
is	O
necessary	O
then	O
to	O
build	O
the	O
electromagnetic	O
devices	O
which	O
enable	O
the	O
construction	O
of	O
useful	O
applied	O
technologies	O
operating	O
within	O
this	O
range	O
.	O
</s>
<s>
These	O
are	O
devices	O
such	O
as	O
directed	O
light	O
sources	O
,	O
lenses	O
,	O
switches	O
,	O
modulators	B-Application
and	O
sensors	O
.	O
</s>
<s>
Terahertz	B-Algorithm
metamaterial	I-Algorithm
devices	O
have	O
been	O
demonstrated	O
in	O
the	O
laboratory	O
as	O
tunable	O
far-infrared	O
filters	O
,	O
optical	B-Algorithm
switching	O
modulators	B-Application
,	O
and	O
metamaterial	O
absorbers	O
.	O
</s>
<s>
The	O
recent	O
existence	O
of	O
a	O
terahertz	B-Architecture
radiating	O
source	O
in	O
general	O
are	O
THz	B-Architecture
quantum	O
cascade	O
lasers	O
,	O
optically	O
pumped	O
THz	B-Architecture
lasers	O
,	O
backward	O
wave	O
oscillators	O
(	O
BWO	O
)	O
and	O
frequency	O
multiplied	O
sources	O
.	O
</s>
<s>
However	O
,	O
technologies	O
to	O
control	O
and	O
manipulate	O
THz	B-Architecture
waves	I-Architecture
are	O
lagging	O
behind	O
other	O
frequency	O
domains	O
of	O
the	O
spectrum	O
of	O
light	O
.	O
</s>
<s>
Furthermore	O
,	O
research	O
into	O
technologies	O
which	O
utilize	O
THz	B-Architecture
frequencies	O
show	O
the	O
capabilities	O
for	O
advanced	O
sensing	B-Architecture
techniques	I-Architecture
.	O
</s>
<s>
In	O
areas	O
where	O
other	O
wavelengths	O
are	O
limited	O
,	O
THz	B-Architecture
frequencies	O
appear	O
to	O
fill	O
the	O
near	O
future	O
gap	O
for	O
advancements	O
in	O
security	O
,	O
public	O
health	O
,	O
biomedicine	O
,	O
defense	O
,	O
communication	O
,	O
and	O
quality	O
control	O
in	O
manufacturing	O
.	O
</s>
<s>
This	O
terahertz	B-Architecture
band	I-Architecture
has	O
the	O
distinction	O
of	O
being	O
non-invasive	O
and	O
will	O
therefore	O
not	O
disrupt	O
or	O
perturb	O
the	O
structure	O
of	O
the	O
object	O
being	O
radiated	O
.	O
</s>
<s>
Terahertz	B-Algorithm
metamaterials	I-Algorithm
,	O
because	O
they	O
interact	O
at	O
the	O
appropriate	O
THz	B-Architecture
frequencies	O
,	O
seem	O
to	O
be	O
one	O
answer	O
in	O
developing	O
materials	O
which	O
use	O
THz	B-Architecture
radiation	I-Architecture
.	O
</s>
<s>
Researchers	O
believe	O
that	O
artificial	O
magnetic	O
(	O
paramagnetic	O
)	O
structures	O
,	O
or	O
hybrid	O
structures	O
that	O
combine	O
natural	O
and	O
artificial	O
magnetic	O
materials	O
,	O
can	O
play	O
a	O
key	O
role	O
in	O
terahertz	B-Architecture
devices	O
.	O
</s>
<s>
Some	O
THz	B-Architecture
metamaterial	O
devices	O
are	O
compact	O
cavities	O
,	O
adaptive	O
optics	B-Algorithm
and	O
lenses	O
,	O
tunable	O
mirrors	O
,	O
isolators	O
,	O
and	O
converters	O
.	O
</s>
<s>
Without	O
available	O
terahertz	B-Architecture
sources	O
,	O
other	O
applications	O
are	O
held	O
back	O
.	O
</s>
<s>
Visible	O
and	O
infrared	O
lasers	O
are	O
at	O
the	O
core	O
of	O
information	B-General_Concept
technology	I-General_Concept
.	O
</s>
<s>
However	O
,	O
applications	O
for	O
the	O
terahertz	B-Architecture
regime	O
,	O
previously	O
defined	O
as	O
the	O
terahertz	B-Architecture
gap	O
of	O
0.1	O
to	O
10	O
THz	B-Architecture
,	O
is	O
an	O
impoverished	O
regime	O
by	O
comparison	O
.	O
</s>
<s>
Sources	O
for	O
generating	O
the	O
required	O
THz	B-Architecture
frequencies	O
(	O
or	O
wavelength	O
)	O
exist	O
,	O
but	O
other	O
challenges	O
hinder	O
their	O
usefulness	O
.	O
</s>
<s>
Terahertz	B-Architecture
laser	O
devices	O
are	O
not	O
compact	O
and	O
therefore	O
lack	O
portability	O
and	O
are	O
not	O
easily	O
integrated	O
into	O
systems	O
.	O
</s>
<s>
In	O
addition	O
,	O
low-power-consumption	O
,	O
solid	O
state	O
terahertz	B-Architecture
sources	O
are	O
lacking	O
.	O
</s>
<s>
Additionally	O
,	O
this	O
lack	O
of	O
appropriate	O
sources	O
hinders	O
opportunities	O
in	O
spectroscopy	O
,	O
remote	B-Application
sensing	I-Application
,	O
free	O
space	O
communications	O
,	O
and	O
medical	B-Application
imaging	I-Application
.	O
</s>
<s>
Meanwhile	O
,	O
potential	O
terahertz	B-Architecture
frequency	O
applications	O
are	O
being	O
researched	O
globally	O
.	O
</s>
<s>
Two	O
recently	O
developed	O
technologies	O
,	O
Terahertz	B-Architecture
time-domain	O
spectroscopy	O
and	O
quantum	O
cascade	O
lasers	O
could	O
possibly	O
be	O
part	O
of	O
a	O
multitude	O
of	O
development	O
platforms	O
worldwide	O
.	O
</s>
<s>
However	O
,	O
the	O
devices	O
and	O
components	O
necessary	O
to	O
effectively	O
manipulate	O
terahertz	B-Architecture
radiation	I-Architecture
require	O
much	O
more	O
development	O
beyond	O
what	O
has	O
been	O
accomplished	O
to	O
date	O
(	O
2012	O
)	O
.	O
</s>
<s>
Compared	O
to	O
interaction	O
with	O
the	O
electric	O
field	O
,	O
the	O
magnetic	O
component	O
is	O
imperceptible	O
when	O
in	O
terahertz	B-Architecture
,	O
infrared	O
,	O
and	O
visible	O
light	O
.	O
</s>
<s>
So	O
,	O
a	O
notable	O
step	O
occurred	O
with	O
the	O
invention	O
of	O
a	O
practical	O
metamaterial	O
at	O
microwave	O
frequencies	O
,	O
because	O
the	O
rudimentary	O
elements	O
of	O
metamaterials	O
have	O
demonstrated	O
a	O
coupling	B-Application
and	O
inductive	O
response	O
to	O
the	O
magnetic	O
component	O
commensurate	O
with	O
the	O
electric	O
coupling	B-Application
and	O
response	O
.	O
</s>
<s>
This	O
demonstrated	O
the	O
occurrence	O
of	O
an	O
artificial	O
magnetism	O
,	O
and	O
was	O
later	O
applied	O
to	O
terahertz	B-Architecture
and	O
infrared	O
electromagnetic	O
wave	O
(	O
or	O
light	O
)	O
.	O
</s>
<s>
In	O
the	O
terahertz	B-Architecture
and	O
infrared	O
domain	O
,	O
it	O
is	O
a	O
response	O
that	O
has	O
not	O
been	O
discovered	O
in	O
nature	O
.	O
</s>
<s>
Moreover	O
,	O
because	O
the	O
metamaterial	O
is	O
artificially	O
fabricated	O
during	O
each	O
step	O
and	O
phase	O
of	O
construction	O
,	O
this	O
gives	O
ability	O
to	O
choose	O
how	O
light	O
,	O
or	O
the	O
terahertz	B-Architecture
electromagnetic	O
wave	O
,	O
will	O
travel	O
through	O
the	O
material	O
and	O
be	O
transmitted	O
.	O
</s>
<s>
The	O
control	O
is	O
also	O
derived	O
from	O
electrical-magnetic	O
coupling	B-Application
and	O
response	O
of	O
rudimentary	O
elements	O
that	O
are	O
smaller	O
than	O
the	O
length	O
of	O
the	O
electromagnetic	O
wave	O
travelling	O
through	O
the	O
assembled	O
metamaterial	O
.	O
</s>
<s>
Electromagnetic	O
radiation	O
,	O
which	O
includes	O
light	O
,	O
carries	O
energy	O
and	O
momentum	B-Algorithm
that	O
may	O
be	O
imparted	O
to	O
matter	O
with	O
which	O
it	O
interacts	O
.	O
</s>
<s>
The	O
magnetic	O
interaction	O
,	O
or	O
induced	O
coupling	B-Application
,	O
of	O
any	O
material	O
can	O
be	O
translated	O
into	O
permeability	O
.	O
</s>
<s>
A	O
few	O
years	O
later	O
,	O
negative	O
permeability	O
was	O
demonstrated	O
in	O
the	O
terahertz	B-Architecture
regime	O
.	O
</s>
<s>
Materials	O
which	O
can	O
couple	O
magnetically	O
are	O
particularly	O
rare	O
at	O
terahertz	B-Architecture
or	O
optical	B-Algorithm
frequencies	O
.	O
</s>
<s>
This	O
reduces	O
the	O
possible	O
useful	O
terahertz	B-Architecture
devices	O
.	O
</s>
<s>
It	O
was	O
noted	O
that	O
the	O
realization	O
of	O
magnetism	O
at	O
THz	B-Architecture
and	O
higher	O
frequencies	O
will	O
substantially	O
affect	O
terahertz	B-Architecture
optics	B-Algorithm
and	O
their	O
applications	O
.	O
</s>
<s>
This	O
has	O
to	O
do	O
with	O
magnetic	O
coupling	B-Application
at	O
the	O
atomic	O
level	O
.	O
</s>
<s>
This	O
drawback	O
can	O
be	O
overcome	O
by	O
using	O
metamaterials	O
that	O
mirror	O
atomic	O
magnetic	O
coupling	B-Application
,	O
on	O
a	O
scale	O
of	O
magnitudes	O
larger	O
than	O
the	O
atom	B-Language
.	O
</s>
<s>
The	O
first	O
terahertz	B-Algorithm
metamaterials	I-Algorithm
able	O
to	O
achieve	O
a	O
desired	O
magnetic	O
response	O
,	O
which	O
included	O
negative	O
values	O
for	O
permeability	O
,	O
were	O
passive	O
materials	O
.	O
</s>
<s>
However	O
,	O
the	O
notable	O
advance	O
,	O
or	O
practical	O
achievement	O
,	O
is	O
actually	O
demonstrating	O
the	O
manipulation	O
of	O
terahertz	B-Architecture
radiation	I-Architecture
with	O
metamaterials	O
.	O
</s>
<s>
However	O
,	O
the	O
demonstration	O
showed	O
a	O
range	O
of	O
0.6	O
to	O
1.8	O
terahertz	B-Architecture
.	O
</s>
<s>
The	O
results	O
were	O
believed	O
to	O
also	O
show	O
that	O
the	O
effect	O
can	O
be	O
tuned	O
throughout	O
the	O
terahertz	B-Architecture
frequency	O
regime	O
by	O
scaling	O
the	O
dimensions	O
of	O
the	O
structure	O
.	O
</s>
<s>
This	O
was	O
followed	O
by	O
a	O
demonstrations	O
at	O
6	O
THz	B-Architecture
,	O
and	O
100	O
THz	B-Architecture
.	O
</s>
<s>
With	O
the	O
first	O
demonstration	O
,	O
scaling	O
of	O
elements	O
,	O
and	O
spacing	O
,	O
allowed	O
for	O
success	O
with	O
the	O
terahertz	B-Architecture
range	O
of	O
frequencies	O
.	O
</s>
<s>
Since	O
it	O
was	O
designed	O
to	O
operate	O
at	O
terahertz	B-Architecture
frequencies	O
,	O
photolithography	O
is	O
used	O
to	O
etch	O
the	O
elements	O
onto	O
a	O
substrate	O
.	O
</s>
<s>
Magnetic	O
responses	O
(	O
permeability	O
)	O
at	O
terahertz	B-Architecture
frequencies	O
can	O
be	O
achieved	O
with	O
a	O
structure	O
composed	O
of	O
non-magnetic	O
elements	O
,	O
such	O
as	O
copper-wire	O
SRR	O
,	O
which	O
demonstrate	O
different	O
responses	O
centered	O
around	O
a	O
resonant	O
frequency	O
.	O
</s>
<s>
Split	O
ring	O
resonators	O
show	O
a	O
capability	O
for	O
tuning	O
across	O
the	O
terahertz	B-Architecture
regime	O
.	O
</s>
<s>
Furthermore	O
,	O
the	O
repeating	O
structure	O
made	O
up	O
the	O
constituent	O
materials	O
follows	O
the	O
same	O
strategy	O
of	O
averaging	O
the	O
electromagnetic	O
field	O
as	O
it	O
manipulates	O
and	O
transmits	O
the	O
terahertz	B-Architecture
radiation	I-Architecture
This	O
averaging	O
technique	O
is	O
called	O
an	O
effective	O
medium	O
response	O
.	O
</s>
<s>
In	O
this	O
terahertz	B-Architecture
experiment	O
ellipsometry	O
is	O
applied	O
,	O
rather	O
than	O
waveguides	O
.	O
</s>
<s>
This	O
fraction	O
is	O
proportional	O
to	O
the	O
field	O
strength	O
and	O
this	O
explains	O
the	O
linear	O
dependency	B-Application
.	O
</s>
<s>
Later	O
,	O
a	O
magnetic	O
response	O
in	O
these	O
materials	O
were	O
demonstrated	O
at	O
100	O
terahertz	B-Architecture
,	O
and	O
in	O
the	O
infrared	O
regime	O
.	O
</s>
<s>
Finally	O
,	O
negative	O
index	O
of	O
refraction	O
was	O
achieved	O
for	O
terahertz	B-Architecture
wavelengths	O
at	O
200	O
terahertz	B-Architecture
using	O
layer	O
pairs	O
metallic	O
nanorods	O
in	O
parallel	O
.	O
</s>
<s>
This	O
work	O
is	O
also	O
complemented	O
by	O
surface	O
plasmon	O
studies	O
in	O
the	O
terahertz	B-Architecture
regime	O
.	O
</s>
<s>
Electromagnetic	O
metamaterials	O
show	O
promise	O
to	O
fill	O
the	O
Terahertz	B-Architecture
gap	O
(	O
0.1	O
–	O
10	O
THz	B-Architecture
)	O
.	O
</s>
<s>
The	O
terahertz	B-Architecture
gap	O
is	O
caused	O
by	O
two	O
general	O
shortfalls	O
.	O
</s>
<s>
First	O
,	O
almost	O
no	O
naturally	O
occurring	O
materials	O
are	O
available	O
for	O
applications	O
which	O
would	O
utilize	O
terahertz	B-Architecture
frequency	I-Architecture
sources	I-Architecture
.	O
</s>
<s>
Second	O
is	O
the	O
inability	O
to	O
translate	O
the	O
successes	O
with	O
EM	O
metamaterials	O
in	O
the	O
microwave	O
and	O
optical	B-Algorithm
domain	O
,	O
to	O
the	O
terahertz	B-Architecture
domain	O
.	O
</s>
<s>
Moreover	O
,	O
the	O
majority	O
of	O
research	O
has	O
focused	O
on	O
the	O
passive	O
properties	O
of	O
artificial	O
periodic	O
THz	B-Architecture
transmission	I-Architecture
,	O
as	O
determined	O
by	O
the	O
patterning	O
of	O
the	O
metamaterial	O
elements	O
e.g.	O
,	O
the	O
effects	O
of	O
the	O
size	O
and	O
shape	O
of	O
inclusions	O
,	O
metal	O
film	O
thickness	O
,	O
hole	O
geometry	O
,	O
periodicity	O
,	O
etc	O
.	O
</s>
<s>
However	O
,	O
little	O
work	O
has	O
focused	O
on	O
the	O
"	O
active	O
"	O
manipulation	O
of	O
the	O
extraordinary	O
optical	B-Algorithm
transmission	O
though	O
it	O
is	O
essential	O
to	O
realize	O
many	O
applications	O
.	O
</s>
<s>
These	O
methods	O
lead	O
to	O
the	O
possibilities	O
of	O
high-sensitive	O
spectroscopy	O
,	O
higher	O
power	O
terahertz	B-Architecture
generation	O
,	O
short-range	O
secure	O
THz	B-Architecture
communication	O
,	O
an	O
even	O
more	O
sensitive	O
detection	O
through	O
terahertz	B-Architecture
capabilities	O
.	O
</s>
<s>
Furthermore	O
,	O
these	O
include	O
the	O
development	O
of	O
techniques	O
for	O
,	O
more	O
sensitive	O
terahertz	B-Architecture
detection	O
,	O
and	O
more	O
effective	O
control	O
and	O
manipulation	O
of	O
terahertz	B-Architecture
waves	I-Architecture
.	O
</s>
<s>
By	O
combining	O
metamaterial	O
elements	O
–	O
specifically	O
,	O
split	O
ring	O
resonators	O
–	O
with	O
Microelectromechanical	B-Architecture
systems	I-Architecture
technology	O
–	O
has	O
enabled	O
the	O
creation	O
of	O
non-planar	O
flexible	O
composites	O
and	O
micromechanically	O
active	O
structures	O
where	O
the	O
orientation	O
of	O
the	O
electromagnetically	O
resonant	O
elements	O
can	O
be	O
precisely	O
controlled	O
with	O
respect	O
to	O
the	O
incident	O
field	O
.	O
</s>
<s>
Terahertz	B-Algorithm
metamaterials	I-Algorithm
are	O
making	O
possible	O
the	O
study	O
of	O
novel	O
devices	O
.	O
</s>
<s>
In	O
the	O
terahertz	B-Architecture
compact	O
moderate	O
power	O
amplifiers	O
are	O
not	O
available	O
.	O
</s>
<s>
These	O
are	O
designs	O
that	O
involve	O
folded	O
waveguide	O
,	O
slow-wave	O
circuits	O
,	O
in	O
which	O
the	O
terahertz	B-Architecture
wave	I-Architecture
meanders	O
through	O
a	O
serpentine	O
path	O
while	O
interacting	O
with	O
a	O
linear	O
electron	O
beam	O
.	O
</s>
<s>
In-house	O
work	O
at	O
the	O
NASA	O
Glenn	O
Research	O
Center	O
has	O
investigated	O
the	O
use	O
of	O
metamaterials	O
—	O
engineered	O
materials	O
with	O
unique	O
electromagnetic	O
properties	O
to	O
increase	O
the	O
power	O
and	O
efficiency	O
of	O
terahertz	B-Architecture
amplification	O
in	O
two	O
types	O
of	O
vacuum	O
electronics	O
slow	O
wave	O
circuits	O
.	O
</s>
<s>
The	O
possibility	O
of	O
controlling	O
radiations	O
in	O
the	O
terahertz	B-Architecture
regime	O
is	O
leading	O
to	O
analysis	O
of	O
designs	O
for	O
sensing	O
devices	O
,	O
and	O
phase	O
modulators	B-Application
.	O
</s>
