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Sensors and Actuators B: Chemical
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ensitivity enhancement of a surface plasmon resonance based biomoleculesensor using graphene and silicon layers
oli Vermaa, Banshi D. Guptaa,∗, Rajan Jhab
Physics Department, Indian Institute of Technology Delhi, New Delhi 110016, IndiaSchool of Basic Sciences, Indian Institute of Technology Bhubaneswar, 751013, India
r t i c l e i n f o
rticle history:eceived 1 May 2011eceived in revised form 2 August 2011ccepted 17 August 2011vailable online 24 August 2011
a b s t r a c t
A surface plasmon resonance based biomolecules sensor using silicon and graphene layers coated overthe base of the high index prism sputtered with gold has been analyzed. The graphene layer has been usedto enhance the adsorption of biomolecules while the addition of silicon layer between gold and grapheneincreases the sensitivity. The thicknesses of gold and silicon layers along with the number of graphenelayers have been optimized to achieve the best performance of the sensor in terms of sensitivity and
eywords:urface plasmonensorensitivityraphene
Full Width at Half Maximum (FWHM). To see the effect of wavelength of the light source, simulationshave been carried out for three different wavelengths. The best performance is obtained for 633 nmwavelength with optimized thicknesses of gold and silicon layers as 40 nm and 7 nm respectively whilethe optimum number of graphene layers is 2. The sensitivity obtained with optimized parameters andadditional silicon layer, is more than twice the value reported in the literature.
iomolecules
. Introduction
During the last two decades remarkable progress has beenade in the development of biosensors for medical diagnostics [1],
nzyme detection, food safety [2], drug diagnostics, etc. These sen-ors utilize various techniques and methods for sensing. Surfacelasmon resonance (SPR) is one of these techniques that have beensed for sensing various chemical and biological parameters includ-
ng refractive index. Surface plasmons are basically the chargeensity oscillations that propagate along the metal–dielectric inter-ace with electric field decaying exponentially in both the medium.he surface plasmons are transverse magnetic (TM) polarized andan be excited by p-polarized light when the propagation con-tant of incident light wave along the interface becomes equalo the propagation constant of the surface plasmon wave (SPW)3,4]. To excite surface plasmons, Kretschmann configuration alongith attenuated total reflection spectroscopy is used [5,6]. Inretschmann configuration, a thin film of a metal is coated on
he base of a high index prism and a p-polarized light of par-icular wavelength impinges from one of the sides of the prismt an angle greater than the critical angle of the prism–metal
nterface. The dielectric medium to be sensed is kept in contact
ith the metal film. The incident light penetrates through theetal film evanescently and excites surface plasmon waves at
metal–dielectric interface resulting in the transfer of energy to theSPW. At a particular angle of incidence, the intensity of the reflectedlight from the prism base is found to be the minimum. This particu-lar angle is called the resonance angle. At this angle the propagationconstants of evanescent wave and of surface plasmon wave becomeequal. The resonance angle depends on the refractive index of thedielectric medium in contact of the metal layer. In a conventionalSPR based sensor, a thin film of noble metal such as gold [7] or sil-ver [8] is used. Out of these two, gold is preferred because of its lowoxidation and high sensitivity.
Surface plasmon resonance based sensor can be used to detectbiomolecules in a liquid sample. When the sample contain-ing biomolecules comes in contact to the metal surface, thebiomolecules get adsorbed on its surface and create a layer of refrac-tive index higher than that of the sample (water) resulting in thechange in resonance angle. The overall performance of the sen-sor depends on the adsorption of the biomolecules. Therefore, thenature of the surface to which biomolecules get adsorbed playsan important role. The disadvantage with gold is that it is a pooradsorbent of biomolecules, thereby limiting the sensitivity of thebiosensor. Recently graphene has emerged as another option toimprove the sensitivity of different types of biosensors. It has beenreported that the addition of graphene layer over gold improvesthe sensitivity of the biosensor [9]. Graphene, discovered recently,
is a single layer of graphite and one atom thick two dimensionalplane of sp2 bonded carbon atoms arranged in honeycomb lattice[10]. It possesses very fascinating optical, mechanical and electricalproperties which have attracted many researchers and scientists all
Fig. 1. Schematic diagram of a prism based SPR probe.
ver the world [11]. The properties include zero band gap [12,13],igh electron mobility, the same mobility for charge carriers (i.e.lectrons and holes), the lowest resistivity of the order of 10−6 [14]nd 2D structure. Due to these properties and relatively low cost,raphene may be used in fabrication of excellent sensors. Further,ts surface to volume ratio is very high for exposing to its surround-ng and hence it is very efficient adsorbent of the biomolecules inomparison to gold. The graphene adsorbs biomolecules stronglyith its carbon based atomic ring structure due to the � stacking
nteraction between its hexagonal cells and the carbon-based ringtructures widely present in bio molecules [15]. Another advantagef graphene is that a number of its layers can be coated on suitableurface in controlled manner. Moreover these layers are quite sta-le because the two layers of graphene are attached with Van deraal forces.Recently, a layer of high refractive index dielectric material such
s silicon over gold has been used to enhance the sensitivity of thePR sensor [16]. This occurs because silicon layer enhances the fieldntensity of the excitation light at the silicon–analyte interface [17].n the present study, to enhance the sensitivity of the SPR sensor foriomolecules, we have added another layer of high index dielectric,ilicon (Si), between gold (Au) and graphene layer. The simulationas been carried out for different thicknesses of gold and silicon
ayers and number of graphene layers. The thicknesses of theseayers and the number of graphene layers have been judiciouslyptimized to obtain the best performance of the sensor. To see theffect of wavelength, the simulations have also been carried out forifferent wavelengths of the light source. The sensitivity obtainedith optimized thicknesses of gold and silicon and the number of
raphene layers is more than two times of that reported recently inhe literature [9]. In addition, the effects of refractive index and thehickness of the adsorbed layer of biomolecules on the sensitivityf the sensor have been reported. The use of silicon layer may alsoelp in sensing of biomolecules efficiently because it increases theobility of electrons in graphene at the surface [18].
. Theory
For simulation, we consider a high index prism coated with thinlm of gold on its base. The base is further coated with silicon andhen graphene. The sensing medium, containing biomolecules toe detected, is placed in contact to graphene layer. As mentionedbove, graphene is a good adsorbent of biomolecules and henceiomolecules get adsorbed at the graphene surface, resulting in andditional layer of slightly higher refractive index than the sens-ng medium. In all, the system consists of six layers namely, prism,
old, silicon, graphene, biomolecules and the analyte that containsiomolecules, as shown in Fig. 1. In addition to these, there cane more than one graphene layer. To excite surface plasmons, p-olarized monochromatic light is incident through one of the faces
tors B 160 (2011) 623– 631
of the prism at an angle greater than the critical angle on the mul-tilayer structure at the base of the prism. The reflected light iscollected through another face of the prism as shown in Fig. 1. Whenthe light is incident on an atomic monolayer of graphene it showshigh opacity [19]. A monolayer of graphene absorbs 2.3% of whitelight and transmits 97.7% [20]. For L numbers of graphene layers,the absorption is L × 2.3% of white light. Therefore it is obvious thattransmission decreases as the number of graphene layers increases.The present SPR sensor is based on angular interrogation method.In this method, the light source is considered as monochromaticwhile the angle of incidence is varied to determine the angle atwhich the intensity of the reflected light reaches minimum. Thedispersive behaviours of all the layers for a given wavelength ofthe light source have been used for calculation and simulation.
2.1. Refractive indices of various layers
In the present study simulations have been carried out for threedifferent wavelengths, 600 nm, 633 nm and 660 nm, of the lightsource. For these three wavelengths of light source, the refrac-tive indices (n1) of the SF10 glass prism used are 1.7276, 1.7230and 1.7205, respectively [21]. The refractive indices of gold (n2)for these wavelengths are obtained from the experimental data ofPalik [22]. The refractive indices of gold used are 0.22028 + i3.0412for 600 nm, 0.1726 + i3.4218 for 633 nm, and 0.16422 + i3.6353 for660 nm wavelengths. The refractive indices (n3) of silicon for threewavelengths used were determined from the following relation[16]:
n3 = A + A1e−�/t1 + A2e−�/t2 (1)
where A = 3.44904, A1 = 2271.88813, A2 = 3.39538, t1 = 0.058304 andt2 = 0.30384; � is the wavelength in �m.
The complex refractive index of graphene is given as [23]
n4 = 3 + iC
3� (2)
where � is the wavelength in �m and the constant C is equal to5.446 �m−1. A single layer of graphene has thickness (dg) equal to0.34 nm and hence for L number of layers its total thickness willbe d4 = L × 0.34 nm[23]. The refractive index of sensing medium isconsidered as 1.33. After the adsorption of biomolecules on thegraphene layer, the change in refractive index and the thicknessof the local sensing medium (biomolecules layer) [24] are denotedby �nbm and d5 respectively.
2.2. Reflection coefficient
We consider the planer waveguide approach and N-layer modelas shown in Fig. 2 to find the reflectivity of the incident p-polarizedlight [25]. In the present study, the number of layers is 6 (N = 6)and all the layers are stacked along the z-direction. The arbitrarymedium layer is defined by thickness dk, dielectric constant εk, per-meability �k, and refractive index nk. The tangential field at the firstboundary Z = Z1 = 0 and the last boundary Z = ZN–1 are related as[
U1V1
]= M
[UN−1VN−1
](3)
where U1 and V1 are the components of electric and magnetic fieldsrespectively at the boundary of the first layer of structure, UN−1and VN−1 are the fields at the boundary of Nth layer and M is thecharacteristic matrix of this structure which is given by
M =N−1∏k=2
Mk (4)
R. Verma et al. / Sensors and Actua
w
fi
r
i
R
aidccit
S
3
astbFdti
Fig. 2. Schematic diagram of an N-layer model.
here
Mk =(
cos ˇk −i sin ˇk/qk
−iqk sin ˇk cos ˇk
)
qk = (εk − n2 sin2 �)1/2
ˇk = dk(2�/�)(εk − n2 sin2 �)1/2
� is the angle of incidence of light with the normal to the inter-ace. The amplitude reflection coefficient (rp) for p-polarized lights
The reflection coefficient of N layer model for p-polarized lights
=∣∣rp
∣∣2(6)
To know the resonance angle, reflection coefficient R is plotteds a function of incident angle �. The angle corresponding to min-mum reflection coefficient (Rmin), called resonance angle (�res), isetermined from the plot. The resonance angle changes with thehange in the refractive index of the sensing medium. Larger thehange better is the performance. If the change in resonance angles ��res corresponding to the change in refractive index �n, thenhe sensitivity of the sensor is defined as
=(
��res
�n
)(7)
. Results and discussion
There are number of design parameters of the sensor that mayffect the performance of the sensor considered in the presenttudy. Some of the critical parameters are thicknesses and refrac-ive indices of different layers such as gold, silicon, graphene andiomolecules in addition to the wavelength of the light source.
or the biomolecules layer we have chosen �nbm = 0.005 and5 = 100 nm. The values of refractive indices of different layers andhe thickness of a single layer of graphene have been discussedn Section 2.1. Using these values, we carried out optimization of
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the thicknesses of gold (d2) and silicon (d3) layers and the num-ber of graphene layers (L) for three different wavelengths (600 nm,633 nm and 660 nm) of the light source [26]. To optimize, we firstdetermine the reflectivity as a function of resonance angle using Eq.(6) and then plot SPR curve to determine the minimum reflectivity(Rmin) and the resonance angle (�res) for a given set of parametersand the refractive index of the biomolecules layer. We then plotRmin and the change in resonance angle for a given change in therefractive index of the biomolecules layer as a function of numberof graphene layers for different sets of values of gold and siliconthicknesses for a given wavelength of the light source. For the opti-mum thicknesses of these layers we focus on the minimum widthof the SPR curve, lowest value of the minimum reflectivity and themaximum change in the resonance angle.
In the angular interrogation method, the reflectivity, as outputsignal, is measured as a function of incident angle and a dip in SPRcurve is obtained at the resonance angle (�res). The energy conser-vation requires that the sum of the absorbance (A), transmittance(T) and the reflectance (R) should be equal to 1. At attenuated totalreflection (ATR) condition, T = 0, and hence A + R = 1. At resonanceangle, ideally reflectance R is also zero (R = 0) which implies A = 1. Itmeans that the total energy of the incident light is absorbed in themedium and the sharpest SPR curve is obtained. This occurs whenthe light beam incident on the prism traverses through metal layeras surface plasmons are generated at the interface which radiateslight back into the metal film. If the thickness of the metal layeris small, the backscattered field increases and since backscatteredwave is out of phase with incident light wave, these two wavesinterfere destructively. Due to this the reflectance reduces to mini-mum and for the optimum thicknesses of layers these compensateeach other and the reflectance becomes zero or the total absorptionoccurs [27]. However, the reflectivity also depends on the wave-length of the incident light in addition to angle of incidence andthe thicknesses of the various layers.
As mentioned earlier, in the present sensor, the prism base iscoated with gold, silicon and graphene sequentially and hence ithas three layers over the prism base. When a sensing sample con-sisting of biomolecules comes in contact to graphene layer, thebiomolecules from sensing sample get adsorbed on the graphenelayer resulting in the formation of a fourth layer of biomoleculeswith refractive index ns + �nbm; ns is the refractive index of thesensing medium or the sample. To optimize parameters, simula-tions have been carried out for different numbers of graphene layersfor given thicknesses of gold and silicon layers. Figs. 3(a)–(c) showthe variations of Rmin with number of graphene layers (L) for differ-ent thicknesses of gold layer assuming no silicon layer for 600 nm,633 nm and 660 nm wavelengths respectively. It may be noted thatthe complete transfer of energy of the incident light to surface plas-mons (R = 0) for a given thickness of gold layer depends on the valueof L. As the thickness of the gold layer decreases the number ofgraphene layers required to transfer complete energy increases.For a given thickness of the gold layer, the number of graphene lay-ers required for the complete transfer of energy further depends onthe wavelength of the light source. As the wavelength of the lightsource increases the dip in the reflectivity curve corresponding toa fixed thickness of the gold film shifts towards the higher numberof graphene layers. In the wavelength range studied, no graphenelayer for minimum reflectivity is required for 50 nm thickness ofgold film, a fact reported in the literature for 50 nm as the opti-mized thickness for gold film. The decrease in the thickness of thegold layer is compensated by the addition of graphene layers forachieving complete transfer of energy to surface plasmons. Fur-
thermore, the increase in the total graphene layers thickness islesser than the decrease in the gold film thickness which may bedue to the higher refractive index of the graphene in comparisonto gold.
626 R. Verma et al. / Sensors and Actuators B 160 (2011) 623– 631
Fig. 3. Variation of minimum reflectivity in SPR curve with different layers ofgraphene for various thicknesses of gold and no layer of silicon for wavelengths (a)6ft
caoid6tnl
Fig. 4. Variation of change in resonance angle due to the adsorption of biomoleculeswith different layers of graphene for various thicknesses of gold and no layer of sili-
00 nm, (b) 633 nm and (c) 660 nm. The symbols correspond to the values obtainedrom the simulated results while the continuous lines are the best fit curves throughhese symbols.
To check the performance of the sensor, we determine thehange in resonance angle (��res) obtained before and after thedsorption of biomolecules present in the sensing medium (water)ver the graphene layer. Figs. 4(a)–(c) show the variations of changen resonance angle as a function of number of graphene layers forifferent thicknesses of gold film and no silicon layer for 600 nm,
33 nm and 660 nm wavelengths respectively. It is observed thathe change in resonance angle increases with the increase in theumber of graphene layers. Further, for a fixed number of graphene
ayers, the change in resonance angle increases with the increase in
con for wavelengths (a) 600 nm, (b) 633 nm and (c) 660 nm. The symbols correspondto the values obtained from the simulated results while the continuous lines are thebest fit curves through these symbols.
the thickness of the gold film. In addition, the change in resonanceangle decreases for fixed values of the thickness of gold film and thenumber of graphene layer as the wavelength increases. However,in all these observations, we have not considered complete transferof energy to surface plasmons that is required for the optimizationof film thickness, number of graphene layers and the wavelength
of the light source for best performance.
The simulations, similar to the above, have also been carriedout for different thicknesses of the silicon layer for the same threewavelengths. Fig. 5 shows the variation of Rmin with the number
R. Verma et al. / Sensors and Actuators B 160 (2011) 623– 631 627
F5
o5tntriwanF
R < 0.03, and the corresponding change in resonance angle for each
ig. 5. Same as Fig. 3 except that in this case the thickness of the silicon layer is nm.
f graphene layers (L) for diffrent thicknesses of gold layer and nm thickness of silicon layer. Comparison of results in Fig. 5 withhose in Fig. 3 implies that the addition of silicon layer decreases theumber of graphene layers required for zero reflectivity for a givenhickness of the gold layer. The correponding plots for the change inesonanace angle (��res) for three wavelengths have been shownn Fig. 6. The trends of the plots are different from those obtained
ithout the silicon layer. It is found that �� first increases up to
res
certain value and then starts decreasing with the increase in theumber of graphene layers for all the thicknesses of the gold layer.urther, the increase in the wavelength of the light source shifts the
Fig. 6. Same as Fig. 4 except that in this case the thickness of the silicon layer is5 nm.
maximum change in resonance angle towards the higher numberof graphene layers and also results in the decrease in its value. InFigs. 7 and 8 we have plotted results similar to Figs. 5 and 6 but for7 nm thickness of the silicon layer. The interpretation of the resultsis the same as for 5 nm thickness of the silicon layer except that thepeak corresponding to maximum change in resonance angle shiftstowards the lower number of graphene layers.
The required number of graphene layers for the complete trans-fer of energy to surface plasmons under the resonance condition,
case are given in Tables 1–3 for wavelengths 600 nm, 633 nm and660 nm respectively. It may be noted that the data presented inthese tables correspond to nearly zero reflectivity only and hence
628 R. Verma et al. / Sensors and Actuators B 160 (2011) 623– 631
Fig. 7. Same as Fig. 3 except that in this case the thickness of the silicon layer is7 nm.
Fig. 8. Same as Fig. 4 except that in this case the thickness of the silicon layer is7 nm.
Table 1Optimized values of thicknesses of gold and silicon and the number of graphene layers with corresponding change in resonance angle and FWHM for zero reflectivity in SPRcurves for 600 nm wavelength.
R. Verma et al. / Sensors and Actuators B 160 (2011) 623– 631 629
Table 2Optimized values of thicknesses of gold and silicon and the number of graphene layers with corresponding change in resonance angle and FWHM for zero reflectivity in SPRcurves for 633 nm wavelength.
Table 3Optimized values of thicknesses of gold and silicon and the number of graphene layers with corresponding change in resonance angle and FWHM for zero reflectivity in SPRcurves for 660 nm wavelength.
sensor as shown in Fig. 11. Thus, any increase in the thickness ofthe biomolecules layer will increase the change in the resonanceangle and hence the sensitivity of the sensor.
nly those combinations of thicknesses and number of grapheneayers are tabulated. In all the tables we have also tabulatedWHM of SPR curves. The maximum change in resonance anglesbtained are 0.56◦, 0.673◦ and 0.544◦ for 600 nm, 633 nm and60 nm wavelengths, respectively. The corresponding FWHM are0.310◦, 17.975◦ and 17.418◦; the last two are nearly the same.hese results imply that the combination of 40 nm gold and 7 nmilicon layer thicknesses with optimized number of graphene lay-rs as 2 and 633 nm as the wavelength of the light source is theptimum to achieve the best performance of the sensor. We havelso carried out simulations for higher thicknesses of silicon layerut for higher thicknesses the SPR curves become broad and fur-her, in none of the cases, complete transfer of energy takes place.rom the tabulated values it can be noted that the change in res-nance angle is lowest when the sensor has only gold layer (noilicon and no graphene layer). If graphene layers are coated overold (no silicon layer) then it marginally increases the change in res-nance angle. If silicon layer is coated over gold layer (no grapheneayer) then the change in resonance angle becomes twice of thatf the gold layer only. Moreover, the addition of graphene layerver silicon further increases the change in resonance angle. Thehange in resonance angle is more than twice of that reported inhe literature [9]. According to these simulations the optimum val-es of the parameters for sensitivity and FWHM for biomoleculesPR sensor are the following: gold layer thickness = 40 nm, sili-on layer thickness = 7 nm, the number of graphene layers = 2 and
= 633 nm.It may be noted that the addition of silicon layer enhances the
aximum value of the change in resonance angle for a particu-ar number of graphene layers. The reason of enhancement of thehange in resonance angle or the sensitivity is the high refractivendex of the silicon layer which increases the field intensity at the
nterface and hence the field penetrates strongly in the analyte17,28]. Based on the studies reported in the literature on the addi-ion of silicon layer, the schematic of the field intensity with the
distance in the direction perpendicular to the prism base may bedepicted as shown in Fig. 9.
In the above simulations we have considered �nbm = 0.005and d4 = 100 nm irrespective of the number of graphene layers. Ifthe change in the local refractive index due to the adsorption ofbiomolecules on graphene layer increases, then the change in res-onance angle (��res) also increases as shown in Fig. 10. This willfurther increase the change in resonance angle and hence the sen-sitivity of the sensor. Rather than this consideration, if we suppose,that the thickness of the biomolecules layer is more than what wehave considered (100 nm thickness of the biomolecules layer), thenmore change in the thickness of the biomolecules layer increasesthe change in the resonance angle and hence the sensitivity of the
Fig. 9. Schematic diagram of the field intensity along the direction perpendicularto the prism base.
630 R. Verma et al. / Sensors and Actua
Fig. 10. Variation of change in resonance angle with the change in refractive indexof the biomolecules layer for 2 layers of graphene with 40 nm and 7 nm thicknessesof gold and silicon layers respectively.
Fig. 11. Variation of change in resonance angle with the thickness of thebg
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iomolecules layer for 2 layers of graphene with 40 nm and 7 nm thicknesses ofold and silicon layers respectively.
. Conclusions
We have analyzed and numerically simulated a surface plasmonesonance based prism sensor using silicon and graphene layersn addition to conventionally used gold layer for the detection ofiomolecules. The graphene layer is used to enhance the adsorptionf biomolecules over it while the addition of silicon layer betweenold and graphene increases the sensitivity significantly. The sim-lations have been carried out for three different wavelengths ofhe light source. The present sensor shows highest sensitivity andetection accuracy for 40 nm thickness of gold, 7 nm thickness ofilicon, 2 layers of graphene and 633 nm wavelength of the lightource. The present study will open a new window for chemicalnd biochemical sensing applications by riding on the advantage ofatest fabrication and characterization techniques to design a highlyensitive and accurate biosensor.
cknowledgements
The present work is partially supported by the Department ofcience and Technology (DST), India. Roli Verma is thankful toouncil of Scientific and Industrial Research (CSIR), India for pro-iding research fellowship.
tors B 160 (2011) 623– 631
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Biographies
Roli Verma received her M.Sc. degree in Physics (2006) and B.Ed. (2007) from C.S.J.M.University Kanpur (India). Since January 2010, Ms. Verma is a full time Ph.D. studentat the Physics Department, Indian Institute of Technology Delhi. Ms. Verma is astudent member of Optical Society of America and holds the position of treasurer of
IIT Delhi student chapter of OSA.
B.D. Gupta received his M.Sc. degree in Physics (1975) from Aligarh Muslim Uni-versity (India) and a Ph.D. degree in Physics (1979) from the Indian Institute ofTechnology, New Delhi. In 1978 he joined the Indian Institute of Technology, NewDelhi, where he is currently a Professor in Physics. In addition, Prof. Gupta has
orked at the University of Guelph (Canada) in 1982–1983, the University of TorontoCanada) in 1985, the Florida State University (USA) in 1988, the University of Strath-lyde (UK) in 1993 and the University of Birmingham (UK) in 2010. In 1992, he waswarded the ICTP Associateship by the International Centre for Theoretical Physics,rieste (Italy), which he held for 8 consecutive years. In this capacity, he visited ICTPItaly) in 1994 and 1996. Prof. Gupta is a recipient of the 1991 Gowri Memorial Awardf the Institution of Electronics and Telecommunication Engineers (India). He hasublished more than 80 research papers including 5 review articles in International
ournal of Repute. Prof. Gupta authored a book entitled Fiber Optic Sensors: Princi-les and Applications (NIPA New Delhi, 2006) and is the co-editor of the Proceedingsf SPIE (USA), vol. 3666 (1998) and Advances in Contemporary Physics and Energysupplement volume) (Allied Publishers, New Delhi). His current areas of interestre plasmonics and fiber optic sensors. He is a regular member of the Optical Society
tors B 160 (2011) 623– 631 631
of America and life member of the Optical Society of India and the Indian Chapterof ICTP.
Rajan Jha received his M.Sc. and Ph.D. degrees from Indian Institute of TechnologyDelhi, India in 2001 and 2007, respectively. From early 2008 to July 2009, he wasa post doctoral researcher at ICFO – The Institute of Photonics Sciences, Barcelona,Spain. He was awarded JSPS (Japanese Society for Promotion of Science) fellowshipin 2009. He is currently working as Assistant Professor in Physics in School of Basic
Sciences at Indian Institute of Technology Bhubaneswar, India. He is a regular mem-ber of Optical Society of America (OSA) and is a life member of Optical Society of India(OSI). His areas of research are optical sensors, nano- & bio-photonics, spectroscopyand imaging, solar cell, waveguide & interferometer. He has published more than20 research articles including a review article in International Journal of Repute.
