The study of photo-electric sensor based on
the slotted photonic crystal waveguide
Daquan Yang, Huiping Tian, Yuefeng Ji
Key Laboratory of Information Photonics and Optical Communications, Ministry of Education,
Beijing University of Posts and Telecommunications, Beijing
yangdq5896@163.com, hptian@bupt.edu.cn, jyf@bupt.edu.cn
function and localize light is broken, which are
Abstract
necessary for these applications. Designing
We present a novel concept of a compact, more
photonic crystals with strong field confinement
sensitive photoelectric sensor, based on the
[4,10-12], small mode volumes, and low
slotted photonic crystal waveguide structures
extinction
that can be realized in two dimensional photonic
interconnects, and higher sensitivity sensors. At
crystal slabs of silicon in Silicon-on-Insulator
present, there are large number of documents
(SOI) as core material employing a nonlinear
and papers ahout the stress sensors[1,7] and
optical polymer as infiltration and cladding
bio-sensors[6,14-16] based on the photonic
material. By applying three-dimensional (3D)
crystals. However, the search of photo-electric
finite-difference
we
sensor based on the photonic crystals in
simulate the change of optical properties
domestic and international research is still in the
(including wavelength and transmission) of the
exploration
W1 silicon photonic crystal waveguide and the
waveguide[2,4,10-12] photonic crystals recently
slotted photonic crystal waveguide, respectively.
reported, that are able to confine light in a
The sensitivity enhancement of more than 30
nanoscale low index region are becoming crucial
times is demonstrated in the slotted photonic
due to the fact that they provide an ideal
crystal
sensor
platform for mode field concentration in the slot
configuration. Besides , the quality (Q) factor
region where other materials can be inserted to
has also been improved significantly.
provide a myriad of new explorations[2].
Keywords: slotted photonic crystal; SOI;
In this paper, we propose a novel concept of a
FDTD; transmission; sensitivity;
compact, more sensitive photo-electric sensor,
time-domain
waveguide
(FDTD),
photo-electric
photo-electric
sensor; quality factor
losses
stage.
enables
Particularly,
lower
the
loss
slotted
based on the polymer-infiltrated slotted photonic
crystal waveguide structures. The ability of
1
Introduction
electro-optical(EO) [9] active polymers to
infiltrate structures on the scale of hundreds of
Photonic crystals (PhC) is a kind of periodic
nanometers had been previously shown to work
dielectric structure with the capability to
from solution [2,8]. To increase the interaction
manipulate light propagation[9], which have
of the external electric field and optical field (i.e.
been studied extensively for many applications,
TE polarization) in the nonlinear polymer region
including optical waveguides and interconnects,
a slot was introduced into the PhC defect
modulators [2,8] and switches, and sensors
waveguide. Finally, using the three-dimensional
[7-16]. When the defects are introduced in
(3D) finite-difference time-domain (FDTD), we
photonic crystals, the periodicity of the dielectric
simulate the change of optical transmission of
Considering a PhCW photo-electric sensor
the W1 silicon photonic crystal waveguide and
without slot as shown in Figure 1, it is
the
waveguide
constructed in a silicon slab (nsi=3.48) by
respectively when the drive voltage increase at
arranging a triangular lattice of air holes
U =0.2V. The sensitivity enhancement of
infiltrated with the polymer (npoly=1.6), where a
more than 30 times is demonstrated in the slotted
single row of air holes is removed. Two
photonic crystal waveguide photo-electric sensor
electrodes have been placed on each side of the
configuration. Besides, the quality (Q) factor has
waveguide. This means that the electrostatic
also been improved obviously.
field lines are parallel to the y axis, allowing the
slotted
photonic
crystal
largest electro-optic coefficien r33 in polystyrene
2
The simulation methods
to be used. In our design, we consider the drive
Two-dimensional photonic crystal lattice hole
and defect hole positions were integrated to
define the complete photonic crystal structure.
Finite-difference time-domain (FDTD) analysis
of the photonic crystal structure was carried out
using software with subpixel averaging for
increased accuracy (meep). All simulations were
voltage (U) between the electrodes as the
varation parameter. By applying the 3D FDTD
method, U is varied from 0 to 1.0v with
step U =0.2V, the transmission spectrum for
TE polarized light-wave in W1 PhCW can be
numerically calculated and analyzed, as shown
in Figure 2.
carried out at the resolution (resolution=10) in
order to obtain consistent comparison results.
The Gaussian source with center frequency
(   0.27(2 c a) )was used and run for several
periods. The simulation area was surrounded by
one-spatial unit thick perfectly matched layer
(PML), which absorbed the fields leaving the
simulated region in order to prevent reflections.
3 The theoretical model and the
simulation result
Figuer 2
Normalized transmission spectra of
the W1 PhCW photo-electric sensor with six
different drive voltage ranging from U=0v to
3.1 Photo-electric sensor based on photonic
U=1.0v in U =0.2v increments.
crystal waveguide without slot
To make the device operate around 1550 nm, the
lattice constant is tailored to a= 426 nm, the bulk
a
hole radius of the PCW is r=0.32a and the slab
Electrode
thickness H=220 nm. The radii of the first two
rows of holes adjacent to the defect are r1=0.3a,
2r2
2r1
Light
r2=0.36a respectively. When the drive voltage
varies from 0 to 1.0v, because of the Pockels
y
npoly
nsi
x
z
Figure 1
Electrode
Structure model of W1 PhCW
photo-electric sensor without slot, where a=426
nm, r = 0.32a, r1 = 0.3a, r2=0.36a.
effect based on electronic displacement the
refractive index of polymer will be changed. The
relationship between the variation of refractive
index of polymer(△n)and the drive voltage (U)
can be defined as follows:
1
U
n    n3poly   33 
2
d
a
(1)
Electrode
Where r33 is the electro-optic coefficient. By
choosing a state of the art polymer material with
r33=150 pm/v, U is the applied modulated
voltage, and d is the width of the waveguide.
2r2
2r1
w
Light
y
nploy
Based on the sensor’s architecture shown as
Figure 1, using the FDTD simulation method,
nsi
x
z
Electrode
the electric field distribution for the sensor at
operating frequency (   0.27(2 c a) ) is
Figure 4
shown in Figure 3. The FDTD simulation result
r1 = 0.3a, r2=0.36a, w=0.25a.
show that the resonance wavelength shifts up by
U = 0.1V, as plotted in Figure 2.
In Figure 3, the resonance wavelength shift 
0.27nm for
is also plotted as a function of variation of the
drive voltage, the sensor’s sensitivity is defined
as:
S=  / U
(2)
The calculated structural varition rate S of the
W1 PhC waveguide photo-electric sensor is
2.7nm/v in the drive voltage measurement range
0-1.0v.
Structure model of slotted PhCW
photo-electric sensor, where a=426 nm, r = 0.32a,
The structure of the slotted PhC waveguide
photo-electric sensor as shown in Figure 4,
where a single row of air holes is removed and
replaced by a narrow air slot. Two electrodes
have been placed on each side of the waveguide.
We also consider the drive voltage (U) between
the electrodes as the varation parameter. By
applying the 3D FDTD method, U is varied from
0 to 1.0v at the U =0.2V, the transmission
spectrum for TE polarized light-wave in slotted
PhC waveguide photo-electric sensor is shown
in Figure 5.
u=0v
u=0.2v
u=0.4v
u=0.6v
u=0.8v
u=1v
0.8
Transimission---(a.u.)
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
Figure 3
The relationship between the applied
drive voltage and the change of output resonance
wavelength is a linear dependence,the sensitivity
of the W1 PhCW sensor is about 2.7nm/v. Insert:
calculated y component of the electic field
distribution for the W1 PhCW sensor at
operating frequency.
3.2
Photo-electric sensor based on photonic
crystal waveguide with slot
1200
Figuer 5
1400
1600
1800
wavelength---(nm)
2000
2200
Normalized transmission spectra of
the slotted PhCW photo-electric sensor with six
different drive voltage ranging from U=0v to
U=1.0v in U =0.2v increments.
In order to obtain consistent comparison results,
all the structural parameters about the slotted
waveguide sensor , such as the lattice constant a,
the hole radius of the PCW r, r1 and r2, and the
slab thickness H, are the same as the W1
waveguide structural parameters except for the
width of the slotted waveguide w, where the
change of peak wavelength--/nm
slotted waveguide width is 0.25a.
100
95
90
85
80
75
70
65
60
55
50
45
40
35
30
25
20
15
10
5
0
slot波 导 结 构
w1波 导 结 构
线性拟合
0
Figure 7
0.2
0.4
0.6
0.8
the voltage between waveguide--/v
1
The relationship between the applied
drive voltage and the change of output resonance
Figure 6
The relationship between the applied
wavelength. The relationships of the sensor
drive voltage and the change of output resonance
sensitivity for the W1 PhCW sensor and the
wavelength
slotted PhCW sensor are presented.
is
a
linear
dependence,
the
sensitivity of the slotted PhCW sensor is about
87nm/v. Insert: calculated y component of the
electic field distribution for the slotted PhCW
sensor at operating frequency
Based on the sensor’s architecture shown in
Figure 4, by applying the FDTD simulation
method, the electric field distribution for the
sensor at operating frequency (   0.27(2 c a) )
is shown in Figure 6. The FDTD simulation
result shows that the resonance wavelength
shifts up about by 9nm for U = 0.1V, as
plotted in Figure 6. In Figure 6, the resonance
wavelength shift  is also plotted as a
function of variation of the drive voltage. The
calculated structural varition rate S of the slotted
PhC waveguide photo-electric sensor is about
87nm/v in the drive voltage measurement range
5
Conclusions
In conclusion, we present a more sensitive
photo-electricsensor, based on the polymer
infiltrated slotted photonic crystal waveguide
structures. Using the three-dimensional (3D)
finite-difference
time-domain
(FDTD),
we
simulate the change of optical transmission
spectrum properties of the W1 PhCW sensor and
the slotted PhCW sensor, respectively. By
comparing with the two different structures of
the sensor, both simulaition and calculation data
demonstrate that the slotted PhCW sensor
exhibits over 30-times sensitivity enhancement
that benefits from the strong restrict of light in a
nanoscale low index region.
Acknowledgement
0-1.0v. In Figure 7, comparing with the PhCW
sensor without slot, we can come to a conclusion
This research was supported in part by NSFC
that the sensitivity of the slotted PhCW
(No. 60707001, No. 60711140087), National
photo-electric sensor configuration is improved
973 Program (No. 2007CB310705), National
more than 30 times.
863 Program (No. 2009AA01Z214), NCET
(07-0110),
SRFDP(200800130001),
PCSIRT
(No.IRT0609), ISTCP(No.2006DFA11040), P. R.
China.
References
[1] Christopher Kang, Sharon M. Weiss,
“Photonic crystal with multiple-hole defect
for sensor applications, ” Opt. Express 22,
waveguides,” Nature 04210, Vol 438,
18188-18193 (2008).
(2005)
[2] XiaonanChen,AlanX.Wang,SwapnajitChak
[10] A. Di Falco, L. O'Faolain, T. F. Krauss,
ravarty,andRayT.Chen,“Electrooptically-Ac
“Slotted Photonic Crystal waveguides and
tive Slow-Light-Enhanced Silicon Slot
cavities
Photonic
applications,” IEEE,( 2008)
Crystal
Waveguides,”
IEEE
for
slow
light
and
sensing
[11] A.DiFalco,L.O’Faolain,andT.F.Krauss,
Journal 5, (2009)
[3] Xuan Zhang, Huiping Tian, Yuefeng Ji,
“Chemical sensing in slotted photonic
“Group index and dispersion properties of
crystal heterostructure cavities,” APPLIED
photonic crystal waveguides with circular
PHYSIC SLETTERS 94,063503 ,(2009)
and square air-holes,” OC (2010)
[12] JunWu,YanpingLi,ChaoPeng,ZiyuWang,
[4] WU Jun, LI YanPing, YANG ChuanChuan,
“Wide bandand low dispersion slow light in
PENG Chao ,WANG ZiYu, “Slow light in
slotted photonic crystal waveguide,” Optics
tapered slot photonic crystal waveguide,”
Communications, (2010)
Chinese Sci Bull, 54: 3658―3662, (2009)
[13] Mehmet A. Dündar, Els C. I. Ryckebosch,
[5] XiaolingWang, ZhenfengXu, NaiguangLu
Richard Nötzel Fouad Karouta,Leo J. van
“Ultracompact
IJzendoorn, and Rob W. van der Heijden,
bJunZhu
,GuofanJin,
refractive
index
on
“Sensitivities of InGaAsP photonic crystal
microcavity in the sandwiched photonic
membrane nanocavities to hole refractive
crystal
index,” Opt. Express 5, 4049-4056 (2010).
sensor
waveguide
based
structure,”
Optics
Communications 281, 1725–1731, (2008)
[6] S. C. Buswell, V. A. Wright, J. M. Buriak, V.
Van1S.
Evoy,
proteins
“Specific
using
detection
photoni
of
ccrystal
waveguides,”Opt.Express 20, 15949-15957,
(2008).
[7] Tsan-Wen
[14] S. C. Buswe, V. A. Wright, J. M. Buriak2 V.
Van1, S. Evoy, “Specific detection of
proteins
using
photonic
crystal
waveguides,”Opt.Express 20, 15949-15957
(2008).
[15] Carlos A. Barrios, Maria Jose Banuls,
Lu
and
Po-Tsung
Lee,
Victoria
Gonzalez-Pedro,
Kristinn
B.
“Ultra-high sensitivity optical stress sensor
Gylfason, Benito Sanchez, Amadeu Griol,
based on double-layered photonic crystal
A. Maquieira, H. Sohlstrom, M. Holgado,
microcavity,” Opt. Express 3, 1518-1526,
and Casquel, “Label-free optical biosensing
(2009).
with slot-waveguides,” Science 317, 783
[8] Jan Hendrik Wülbern,Alexander Petrov,
(2007).
“Electro-optical
[16] Mindy Lee and Philippe M. Fauchet,
modulator in a polymer-infiltrated silicon
“Two-dimensional silicon photonic crystal
slotted
waveguide
based biosensing platform for protein
heterostructure resonator” Opt. Express, 1,
detection,” Opt. Express 8, 4530-4535
303 -313, (2008).
(2007).
and
Manfred
photonic
Eich,
crystal
[9] YuriiA.Vlasov,MartinO’Boyle,HendrikF.Ha
mann1ShareeJ.McNab, “Active control of
slow light on a chip wit hphotonic crystal