International Journal of Advancements in Research & Technology, Volume 4, Issue 1, January -2015
ISSN 2278-7763
37
LAYOUT DESIGN OF PHOTONIC CRYSTAL
BASED LIQUID REFRACTIVE INDEX SENSOR
Harshada J Patil1, Indumathi T.S2, Preeta Sharan3
1
Vemana Institute of Technology,Bangalore,India
2
3
VTU, Bangalore, India
TOCE, Bangalore, India
jharshadap@gmail.com1,sharanpreeta@gmail.com3
Abstract: A simple fluid detection scheme based on
light propagation through 2D photonic crystal having
line defect to create a linear waveguide is proposed
for various fluids. Line defect offers a significant
increase in defect surface area without the trade-off
of the photonic crystal. Because of the sharp
spectrum signal and relatively larger testing region
for liquids the sensor response is faster and was
highly sensitive which offered the sensitivity of
0.000288 RIU. The Q-factor calculated as 134897.
The defect is simulated using finite difference time
domain (FDTD) method using MEEP and MPB
tools. Case studies for Kerosene, Heptanes, Cotton
seed oil, Methanol, Cresol, Acetic acid are done.
Thus the two dimensional photonic crystal based
liquid sensor has been designed to provide the easy to
operate and real time mode measurement in chemical
industries where these liquids are either the part of
the manufacturing process or the part of the final
product.
optoelectronics, μ-wave technologies, quantum
engineering, bio-photonics, acoustics, and so on.
Photonic bandgap devices are used in many
applications such as waveguides and interconnect
optical modulation and switching, light emission and
sensor applications [2-6]. The optical analogy is the
photonic crystal, in which the atoms or molecules are
replaced by macroscopic media with differing
dielectric constants, and the periodic potential is
replaced by a periodic dielectric function (or,
equivalently, a periodic index of refraction). If the
dielectric constants of the materials in the crystal are
sufficiently different, and if the absorption of light by
the materials is minimal, then the refractions and
reflections of light from all of the various interfaces
can produce many of the same phenomena for
photons (light modes) that the atomic potential
produces for electrons [1]. One solution to the
problem of optical control and manipulation is thus a
photonic crystal, a low-loss periodic dielectric
medium. In particular, we can design and construct
photonic crystals with photonic band gap, preventing
light from propagating in certain directions with
specified frequencies (i.e., a certain range of
wavelengths, or “colours,” of light). Photonic crystal
can allow propagation in anomalous and useful ways.
Sensing application requires the defect to be an air
hole of size sufficiently different than the
surrounding photonic crystalic holes [6]. In order to
increase the light interaction in photonic crystals with
air hole defects, we propose a line defect which
increases the surface area in the defect region as well
as maintained the high quality factor.
IJOART
Keywords: 2D photonic crystal, line defect, FDTD,
photonic band gap
Introduction:
Photonic crystals are artificial multi-dimensional
periodic structures with a period of the order of
optical wavelength [1]. They have many analogies to
solid state crystals. The most important one is the
band of photons, which is a powerful theory for the
understanding of light behaviour in a complex
photonic crystal structure. It enables us to create the
photonic band gap and the localization of light. They
have great potentials for novel applications in optics,
Copyright © 2015 SciResPub.
IJOART
International Journal of Advancements in Research & Technology, Volume 4, Issue 1, January -2015
ISSN 2278-7763
The most important feature of photonic
crystal is the existence of a photonic band gap, which
is a forbidden gap of photons. In this gap, light
cannot enter the crystal and electrons cannot emit
photons inside the crystal[4]. The doping of an
impurity optical atom or defect creates the opposite
situation, the strong localization of a resonant photon.
These phenomena will allow a perfect control of light
propagation and radiation. Since the photonic band
gap crystal acts as an insulator of light, flexible and
dense photonic circuit similar to VLSI will be
realized.
The light velocity will be changed from
vacuum velocity c to zero (stopping condition), so the
light matter interaction will be arbitrarily controlled.
The spontaneous emission, which is normally
dominated by the random thermal process, will be
artificially engineered so that it perfectly contributes
to a useful emission [3].
Other unique phenomena are also found in
complex photonic bands. A careful design of a crystal
provides the super prism phenomenon that indicates
an extraordinary large steering of light beam, a
guiding of light beam with no waveguide structures, a
negative refraction that enables peculiar focusing and
imaging of light, the left-handed light propagation
supported by the negative permeability and
permittivity, an extraordinary large group velocity
dispersion that manipulates an optical pulse, etc.
38
……(1)
Here, 'P' is power, 'E' and 'H' is electric and
Magnetic fields,' ' is the frequency.
iii) Sensor design
The design of the sensor consists of the two
dimensional square lattice photonic crystal structure
[f]with line defect carved,in rods (silicon) in air
configuration. The designed model is illustrated in
the Fig 1.
IJOART
ii) Algorithm
The Finite difference Time Domain (FDTD) method
is implemented using the simulation tool MEEP. The
Finite Difference Time Domain method solves the
Input
Source
time domain Maxwell's equation. The method divides
Fig 1: Design of photonic crystal based liquid
the field in time and space and solves for electric and
sensor.
magnetic fields. MEEP is a simulation tool developed
The design and simulation is done with the help of
by MIT for design, model and stimulate various
MEEP tool. The design parameters are given below:
photonic crystal structures [14]. It is a time domain
tool and implements the FDTD method. The
transmission and the reflection spectrum are obtained
using the MEEP tool [d]. MEEP solves the Poynting
vector (Equation 1) and computed the fluxes.
Copyright © 2015 SciResPub.
Photonic
crystal
spectrum
analyzer
1) Rods in air configuration
2) Square lattice structure
3) Lattice constant 'a'=1μm
4) Radius of rods 'r'=0.19μm
IJOART
International Journal of Advancements in Research & Technology, Volume 4, Issue 1, January -2015
ISSN 2278-7763
5)
Dielectric constant of silicon rods =11.56
6)
Dielectric constant of back ground is changed
39
with respect to chemicals
7)
Wavelength of light=1550nm.
As the liquids are adsorbed on the photonic
crystal [12], the refractive index profile of the
photonic crystal changes, as a result the transmitted
and reflected flux values changes. The change [13] in
the transmitted flux is observed for the different
liquids.
iv.Results
The transmission spectrum plot for frequency
Fig 2: transmission spectrum for frequency shift
spectrum is illustrated in the Fig 2. The x-axis
indicates normalised frequency and the y-axis
The x-axis indicates the wavelength in μm and the y-
IJOART
indicates transmission flux for the corresponding
axis represents transmission flux values for the
wavelength. It can be observed that as the change in
corresponding wavelengths in Fig 3 and Fig 4.
the refractive index is slight; the change in the
transmission spectrum is visibly distinct, proving the
sensor to be very sensitive to sense different liquids
from
Fig
2.
The transmission
spectrum
for
wavelength spectrum is illustrated in Fig 3. Distinct
shifts are observed for different liquids. The region at
peak wavelength was derived from Fig 3 and it is
shown in Fig 4.
Fig 3 :wavelength shift for different liquids
Copyright © 2015 SciResPub.
IJOART
International Journal of Advancements in Research & Technology, Volume 4, Issue 1, January -2015
ISSN 2278-7763
40
Table I. peak wavelength and shift in wavelength
observed after simulation
The designed sensor is converted into GDSII file
using IPKISS software using python tool and it is
viewed in GDSII viewer (OWLVISION) and it is
shown in Fig 5. Then it can be easily translated into
ASCII format which will be used for fabrication.The
GDSII file was then verified with respect to its
rulings with the help of K-layout tool and it is shown
in Fig 6.
Fig 4 : transmission spectrum for wavelength shift
IJOART
Analyzing these graphs, it can be said that the design
sensor is very sensitive to chemical variation in air.
The Q-factor has been calculated for the proposed
design & its value is 134837. The sensitivity is
calculated as 0.000288 RIU. The sensitivity was
calculated using the formula, S 

where  =

change in wavelength in nm and  = change in
Fig 5: GDSII file from OWLVISION (GDS viewer
tool)
refractive index.
The shift in wavelength for different liquids is
described in the table I. By maintaining this data one
can easily differentiate liquids present in air or water.
Material
Peak
frequency
Peak
wavelength
air
0.2725
1.835
acetic acid
0.2833
1.7464
cresol
0.2729
1.832
cotton seed oil
0.3015
1.658
hepthane
0.30149
1.6579
kerosene
0.3051
1.639
methanol
0.2831
1.766
Fig 6: GDSII file from K-layout (GDS viewer tool)
Copyright © 2015 SciResPub.
IJOART
International Journal of Advancements in Research & Technology, Volume 4, Issue 1, January -2015
ISSN 2278-7763
41
detection”, Optics Express 15, 4530- 4535(2007).
V.Conclusion
The sensor design consists of a two dimensional
square lattice photonic crystal structure with a line
defect. It is simulated and analysed for detecting
different liquids in air and water. Visibly distinct shift
in both wavelength and frequency are observed,
proving the sensor to be sensitive to even a smallest
change in the input liquid. Photonic crystal
structurewith line defect provides better sensitivity as
compared to other photonic crystal design or other
optical fiber sensor design. The sensor has sensitivity
of the order of 0.000288 /RIU and the spectrum
shows distinct shifts in both frequency and
wavelength. The design meets the fabrication
requirements as the quality factor obtained is 134837.
References
[1].Optical properties of photonic crystals – K
Sakoda.
[7].Photonic crystals modeling the flow of light by
John D.Joannopoulos ,Steven G.Johnson, Robert D.
Meade.
[8].Guided modes in photonic crystal slabs- Steven G.
Johnson, Shanhui Fan, Pierre R. Villeneuve, and J.
D. Joannopoulos, Department of Physics,
Massachusetts Institute of Technology,
Cambridge,Massachusetts 02139 -- PHYSICAL
REVIEW B – AUGUST 1999.
[9].Structural Tuning of Guiding Modes of LineDefect Waveguides of Silicon-on-Insulator Photonic
Crystal Slabs -Masaya Notomi, A Shinya, K
Yamada,J Takahashi, C Takahashi, and I YokohamaIEEE JOURNAL OF QUANTU
ELECTRONICS, VOL. 38, NO. 7, JULY 2002.
[10].Existence of a photonic band gap in two
dimensions-- R. D.Meade, A. M. Rappe, K. D.
Brommer and J. D. Joannopoulos - Appl. Phys. Lett.
61, 495 (1992).
IJOART
[2].Mekis A, Chen J C, Kurland I, Fan S, Villeneuve
P R and Jonnopoulous J D, “High transmission
through sharp bends in photonic crystal
waveguides,” Phys. Rev. Lett.77, 3787- 3790(1996).
[3].Baba T, Fukaya N. And Yonekura J,
“Observation of light propagation in photonic crystal
optical waveguides
with bends”, Electron.Lett.35,654- 655(1999).
[4]. Chutinan A, and Noda S, “Highly confined
waveguides and waveguide bends in threedimensional photonic crystal”, Appl. Phys. Lett.
75,3739-3741(2000).
[5].Tokushima M, Kosaka H, Tomita A and Yamada
H, “Lightwave propagation through a 1200 sharply
bent single-line-defect photonic crystal waveguide”
Appl. Phys. Lett. 76, 952-954(2000).
[6].Lee M, and Fauchet P M, “Two-dimensional
silicon photonic crystal based biosensing platform
for protein
Copyright © 2015 SciResPub.
[11]. “optics and MEMS”, Walker and Nagel, Naval
Research Labs, NRL/MR-99-6336- 7975 (downloadable).
[12]“Fiber Optic Sensors for Detection of Toxic and
BiologicalThreats” Mahmoud El-Sherif *, alitkumar
Bansal and Jianming Yuan ISSN 1424-8220© 2007
by MDPIwww.mdpi.org/sensors.
[13]“Fibre Optic Sensors for Selected Wastewater
Characteristics “Su Sin Chong 1, A. R. Abdul Aziz
1,* and Sulaiman W. Harun2 .ISSN 14248220.www.mdpi.com/journal/sensors .
[14]“Tunableultracompact electro-optical photonic
crystal ring resonator” Cheng-Yang Liu* Journal of
Modern Optics, 2013Vol. 60, No. 16, 1337–1342,
http://dx.doi.org/10.1080/09500340.2013.837979.
[15]“Photonic Crystals: From Theory to Practice”
bySteven G. Johnson.
IJOART