International Journal of Advancements in Research & Technology, Volume 4, Issue 1, January ISSN

International Journal of Advancements in Research & Technology, Volume 4, Issue 1, January -2015 ISSN 2278-7763 37 LAYOUT DESIGN OF PHOTONIC CRYSTAL...
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International Journal of Advancements in Research & Technology, Volume 4, Issue 1, January -2015 ISSN 2278-7763

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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

[email protected],[email protected]

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.

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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,

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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.

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……(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.

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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.

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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

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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

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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-

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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

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International Journal of Advancements in Research & Technology, Volume 4, Issue 1, January -2015 ISSN 2278-7763

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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

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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)

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International Journal of Advancements in Research & Technology, Volume 4, Issue 1, January -2015 ISSN 2278-7763

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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).

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[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

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[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.

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