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SPR sensors based on multilayer diffraction gratings and comparison with prism couplers. 指導教授 : 林啟萬 研究生 : 蘇明啟 日期 : 2004/3/24. outline. Introduction to SPR sensor based on diffraction gratings Characterization of gratings Application of multilayer gratings as optochemical sensors - PowerPoint PPT Presentation
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SPR sensors based on multilayer diffraction gratings and comparison with prism couplers
指導教授 : 林啟萬研究生 : 蘇明啟日期 : 2004/3/24
outline• Introduction to SPR sensor based on diffraction g
ratings• Characterization of gratings• Application of multilayer gratings as optochemica
l sensors• Sensitivity of SPR sensors using prism couplers• Sensitivity of SPR sensors using diffraction grati
ngs• Discussion• Reference
Three major approaches to optical excitation of SPW
prism coupling waveguide coupling
grating coupling
A SPR sensor based on diffraction grating
2
2
)sin(amr
amra n
nmn
Au 45nm652nm
18nm
AFM image of diffraction grating
Cross section of multilayer structures with diffraction grating
形成 Schottky Junction
Au or Ag film
Upper layer
Intermediate layer
substrate
6570
75Ψ
Δ
ε1
ε2
The quality of SPR is increased
When the void contents decrease.
(1) He-Ne laser
(2) Polarizer
(3) Quartz cuvette with tested solution
(4)(5) light beam direction through the cuvette without solution
(6) The same as (5), but for cuvette with tested solution
(7) Cr film-10nm / Au film-45nm
(8) GaAs substrate with diffraction grating
Schematic diagram of opto-chemical sensor
Incident angle vs. reflectance
SiOx thickness
1. 0 nm
2. 3 nm
3. 6 nm
4. 9 nm
5. 12 nm
6. 15nm
Wavelength at 632.8nm
650nm
3nm
The dependencies of the refractive index on the thickness of SiOx film
1. Multi-Angle-of-Incidence ellipsometry
2. SPR technique
The SPR photoresponse/angle dependencies for Ag/GaAs photodetector at different wavelengths
1. 650 nm
2. 625 nm
3. 600 nm
4. 550 nm
5. 500 nm
Metal thickness is 60nm
The SPR photoresponse curves for an Au-Cr-GaAs sensor as function of incidence angle obtained with various concentration
Alcohol in water (vol.%)
1. 0
2. 7.3
3. 13.6
4. 19.2
5. 24.0
6. 28.3
Water in alcohol (vol.%)
1. 0
2. 11.2
3. 20.2
4. 27.5
5. 33.6
6. 38.8
7. 43.7
Note:
Just measure the angle relative to one for a standard sample, instead of measuring absolute angle, because the accuracy of the absolute angular measurement is lower than that of the relative angular measurement.
http://home.hccnet.nl/ja.marquart/BasicSPR/BasicSpr01.htm
ko free space wavenumber
na refractive index of the dielectric (analyte)
np refractive index of the prism coupler
θ the angle of incidence (in the prism)
metal) theofconstant c(dielectri mimrm i
Sensitivity of SPR sensors using prism couplers
spwamr
amrpx k
n
nknkk
2
2
00 )sin(
0k
kn spwef
The effective index of SPW as a function of the wavelength for SPW propagating along the metal-analyte interface for two different values of the refractive index of analyte.
在相同的 na 下 ,Au 的 nef 都比 Ag高
因為 εmr(Au) < εmr(Ag)
nnndn
dS
amramr
mrmr
aP
22
A. Angular interrogation
from spwamr
amrpx k
n
nknkk
2
2
00 )sin(
22
1
aP
PPnn
SS
短波長時 , 有較高的 sensitivity
長波長時 ,sensitivity 較不隨波長變化而改變
故可簡化為
Prism - metal - analyte
(50nm) (na=1.32)
B. Wavelength interrogation
P
aPmramr
mra
mr
aP
nn
ddn
nddndn
dS
23
2
2
dd
nSS
mra
mrPP
3
22
在短波長時 , 很小
所以可以把分母第二項省略
得到
ddnP
Prism - metal - analyte
(50nm) (na=1.32)
Sensitivity of SPR sensors using diffraction gratings
2
2
)sin(
'
amr
amra
xmx
n
nmn
kmGk
m the order of diffracted waves
θ the angle of incidence of the optical wave
Λ the pitch of the grating
G grating vector
Grating depth 70 nm
Grating pitch 800nm
Resonant angle of incidence as a function of the wavelength for gold coated grating (Λ=800nm) and two different refractive indices of analyte
m=1 na ↑ θ↑
m=-2 na↑ θ↓
A. Angular interrogation
)sin()cos(
1
coupler grating th thecontact wiin not is analyte theif
)sin()cos(
1
coupler grating th thecontact wiin is analyte theif
2
2
3
2
amr
mr
aaG
amr
mr
aaG
nndn
dS
nndn
dS
from
2
2
)sin(amr
amra n
nmn
Grating depth 70 nm
Grating pitch 800nm
B. Wavelength interrogation
aG
mr
amrmr
a
amr
a
amr
mr
a
aG
nS
dd
n
nm
n
nnn
m
dn
dS
2 2
32
3
2
2
2
分子及分母的第二項皆遠小於第一項 , 所以可以簡化為
Grating depth 70 nm
Grating pitch 800nm
Discussion I• 利用角度調變時 在短波長時 , 靈敏度較高 但 grating-based 較為複雜 SPθdepends on na/np
SGθdepends on m
m=1 λ=800nm SGθ 只有 0.5 倍的 SPθ
m=2 λ=630nm SGθ 約等於 SPθ
λ=830nm SGθ 約比 SPθ 高出 10%
在長波長時 ,accuracy χ=s/w 較高 λ=630nm χP=15RIU-1
χG=11RIU-1
λ=830nm χP=83RIU-1
χG=48RIU-1
在長波段時 , 金屬材料的選擇 (Au 或 Ag) 則較不重要 See P11
w denote the full-width-half-
maximum of SPR dip
s denote the sensitivity
• 利用波長調變時 在長波段有較高的靈敏度 但 grating-based 的方式遠小於 prism-coupler
λ=630nm χP=108RIU-1
χG=48RIU-1
和角度調變比較 , 利用波長調變的方式 , 可得到較佳的 accuracy, 因此 resolution 也較高
但和角度調變相同的是 χP > χG
Discussion II
Discussion III• grating-based sensor 雖然靈敏度不如 prism-coupled sensor, 但擁有
體積微小化的優點 , 更適合於可攜式系統或植入式系統的應用。
Reference• N.L. Dmitruk, O.I. Mayeva, S.V. Mamykin, O.B. Yastrubchak, M. Klopfleisch,
Characterization and application of multilayer diffraction gratings as optochemical sensors, Institute for Physics of Semiconductors, National Academy of Sciences, Ukraine; Technical University, Germany, Sensors and Actuators A. Physical, September 2000
• Jiri Homola, Ivo Koudela, Sinclair S. Yee, Surface plasmon resonance sensors based on diffraction gratings and prism couplers: sensitivity comparison, Electrical Engineering Department, UW,USA; Institute of Radio Engineering and Electronics, Czech Republic, Sensors and Actuators B. Chemical, 1999
• N.L. Dmitruk, O.I. Mayeva, O.B. Yastrubchak, S.V. Mamykin, Multilayer Gratings: Characterization and Application, Institute of semiconductor physics of NAS of Ukraine, IEEE 1999
• Jiri Homola, On the sensitivity of surface plasmon resonance sensors with spectral interrogation, Institute of Radio Engineering and Electronics AS CR, Czech Republic, Sensors and Actuators B. Chemical, 1997
Thank You!!