Optik
125 (2014) 154–
158
Contents
lists
available
at
ScienceDirect
Optik
j
o
ur
nal
hom
epage:
www.elsevier.de/ijleo
Research
on
terahertz
photonic
crystal
fiber
characteristics
with
high
birefringence
Zhigang
Zhang
a,b
,
Jian
Tang
b
,
Deng
Luo
b
,
Ming
Chen
a,b,∗
,
Hui
Chen
a,b
,
Haiou
Li
a,b
,
Mingsong
Chen
a,b
,
Zhiyi
He
a,b
,
Ning
He
a,b
,
Qian
He
c
a
Guangxi
Experiment
Center
of
Information
Science,
Guilin
University
of
Electronic
Technology,
Guilin
541004,
China
b
Photoelectric
Technology
Research
Institute,
School
of
Information
and
Communication,
Guilin
University
of
Electronic
Technology,
Guilin
541004,
China
c
State
key
Laboratory
of
Networking
and
Switching
Technology,
Beijing
University
of
Posts
and
Telecommunication,
Beijing
100876,
China
a
r
t
i
c
l
e
i
n
f
o
Article
history:
Received
29
January
2013
Accepted
5
June
2013
Keywords:
Photonic
crystal
fiber
High
birefringence
Chromatic
dispersion
Confinement
loss
a
b
s
t
r
a
c
t
A
new
high
birefringence
photonic
crystal
fiber
is
proposed
within
the
terahertz
frequency
region.
It
has
two
types
of
claddings,
the
inner
is
composed
of
six
ellipse
air
holes
arranged
in
a
honeycomb
array
and
the
outer
surrounded
by
circle
holes.
By
using
the
full
vector
finite
element
method
with
anisotropic
perfectly
matched
layers
absorption
boundary
condition,
the
birefringence,
chromatic
dispersion
and
confinement
loss
of
the
fundamental
mode
are
evaluated.
The
results
show
that
the
birefringence
can
achieve
10
−3
when
the
wavelength
increases
from
600
m
to
900
m.
This
structure
will
provide
some
reference
value
for
the
designing
of
high
birefringence
terahertz
photonic
crystal
fiber.
© 2013 Elsevier GmbH. All rights reserved.
1.
Introduction
Terahertz
(THz)
radiation
refers
to
the
electromagnetic
waves
covering
the
wavelength
from
30
m
to
3000
m.
Recently
much
attention
has
been
paid
to
the
THz
radiation
since
it
is
widely
used
in
imaging
[1],
medicine
[2],
sensing
[3],
etc.
However,
it
is
difficult
to
control
and
guide
the
THz
radiation
in
the
free
space.
And
the
THz
radiation
is
severely
absorbed
by
the
vapor
in
the
free
space
[4].
To
overcome
these
difficulties,
THz
waveguide
has
been
chosen
for
its
transmission.
Until
now,
many
kinds
of
THz
waveguides
have
been
reported,
such
as
parallel
plates
[5,6],
bare
metal
wires
[7],
traditional
microwave
waveguides
[8]
and
photonic
crystal
fibers
[9,10].
In
this
paper,
we
focus
on
the
photonic
crystal
fibers.
Photonic
crystal
fibers
(PCFs)
have
attracted
growing
interest
over
the
last
decade
since
first
proposed
in
1996
[11].
Compared
with
the
conventional
optical
fibers,
PCFs
possess
many
unique
properties
such
as
broadband
single-mode
operation
[12],
control-
lable
dispersion
[13,14],
high
birefringence
[15,16]
and
so
forth.
According
to
their
propagation
mechanisms,
there
are
two
kinds
of
PCFs,
namely
index-guiding
PCFs
and
photonic
bandgap
guiding
PCFs.
Due
to
the
large
effective
refractive
index
difference
between
the
core
and
the
cladding,
PCFs
become
one
of
the
most
versatile
platforms
for
the
design
of
various
high
birefringence
THz
PCFs.
∗
Corresponding
author
at:
Guangxi
Experiment
Center
of
Information
Science,
Guilin
University
of
Electronic
Technology,
Guilin
541004,
China.
E-mail
address:
mchenqq2011@gmail.com
(M.
Chen).
Several
high
birefringence
THz
PCFs
have
been
reported
previously
[17–20]
.
In
this
paper,
a
traditional
index-guiding
high
birefringence
THz
PCF
is
introduced.
We
consider
that
the
traditional
index-guiding
PCFs
are
relatively
easily
realized.
So
it
is
important
to
investigate
the
traditional
index-guiding
high
birefringence
THz
fiber
for
prac-
tical
applications.
The
properties
of
birefringence,
dispersion
and
confinement
loss
are
studied
by
optimizing
the
structure
param-
eters
of
the
proposed
PCF.
This
structure
may
be
helpful
for
the
design
and
fabrication
of
traditional
index-guiding
high
birefrin-
gence
THz
PCFs
in
the
future.
2.
Structure
of
the
THz
PCF
and
simulation
method
Fig.
1
shows
the
cross
section
structure
of
the
proposed
high
birefringence
THz
PCF.
The
heavy
gray
areas
represent
high-density
polyethylene
(HDPE)
material
with
low
absorption
in
the
THz
fre-
quency
region.
The
white
areas
are
air
holes.
The
refractive
index
of
the
HDPE
material
and
the
surrounding
air
are
1.53
[21]
and
1,
respectively.
The
structural
parameters
of
the
PCF
are
as
follows.
is
the
hole-to-hole
spacing
and
d
represents
the
diameter
of
the
circle
air
holes.
a
and
b
are
the
major
axis
and
minor
axis
of
the
ellip-
tical
air
holes,
respectively.
The
six
elliptical
air
holes
are
arranged
in
a
honeycomb
array
and
have
the
same
parameters.
Several
numerical
simulation
methods
can
be
used
to
cal-
culate
the
PCFs
such
as
the
plane-wave
expansion
method,
localized-function
method,
finite
difference
method,
full-vector
0030-4026/$
–
see
front
matter ©
2013 Elsevier GmbH. All rights reserved.
http://dx.doi.org/10.1016/j.ijleo.2013.06.074