SPR sensors based on multilayer diffraction gratings and
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 • Sensitivity of SPR sensors using prism couplers • Sensitivity of SPR sensors using diffraction gratings • Discussion • Reference
Three major approaches to optical excitation of SPW prism coupling waveguide coupling grating coupling
A SPR sensor based on diffraction grating 18 nm 652 nm Au 45 nm
AFM image of diffraction grating Cross section of multilayer structures with diffraction grating Upper layer 形成Schottky Junction Au or Ag film Intermediate layer substrate
Δ 65 70 Ψ 75 ε 1 ε 2 The quality of SPR is increased When the void contents decrease.
Schematic diagram of opto-chemical sensor (1) He-Ne laser (2) Polarizer (3) Quartz cuvette with tested solution (4)(5) light beam direction through the cuvette without solution (5) (6) The same as (5), but for cuvette with tested solution (6) (7) Cr film-10 nm / Au film-45 nm (7) (8) Ga. As substrate with diffraction grating
3 nm 650 nm Incident angle vs. reflectance Si. Ox thickness 1. 0 nm 2. 3 nm 3. 6 nm 4. The dependencies of the refractive index on the thickness of Si. Ox film 1. Multi-Angle-of-Incidence ellipsometry 2. SPR technique The SPR photoresponse/angle dependencies for Ag/Ga. As photodetector at different wavelengths 1. 650 nm 2. 625 nm 9 nm 3. 600 nm 5. 12 nm 4. 550 nm 6. 15 nm 5. 500 nm 7. Wavelength at 632. 8 nm 6. Metal thickness is 60 nm
The SPR photoresponse curves for an Au-Cr-Ga. As sensor as function of incidence angle obtained with various concentration Alcohol in water (vol. %) Water in alcohol (vol. %) 1. 0 Note: 2. 7. 3 2. 11. 2 3. 13. 6 3. 20. 2 4. 19. 2 4. 27. 5 5. 24. 0 5. 33. 6 6. 28. 3 6. 38. 8 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. 7. 43. 7
Sensitivity of SPR sensors using prism couplers 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) http: //home. hccnet. nl/ja. marquart/Basic. SPR/Basic. Spr 01. htm
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)
A. Angular interrogation from 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 (50 nm) (na=1. 32)
B. Wavelength interrogation 在短波長時, 很小 所以可以把分母第二項省略 得到 Prism - metal - analyte (50 nm) (na=1. 32)
Sensitivity of SPR sensors using diffraction gratings m the order of diffracted waves θ the angle of incidence of the optical wave Λ the pitch of the grating G grating vector
Resonant angle of incidence as a function of the wavelength for gold coated grating (Λ=800 nm) and two different refractive indices of analyte m=1 na ↑ θ↑ m=-2 na↑ Grating depth 70 nm Grating pitch 800 nm θ↓
A. Angular interrogation from Grating depth 70 nm Grating pitch 800 nm
B. Wavelength interrogation Grating depth 70 nm Grating pitch 800 nm 分子及分母的第二項皆遠小於第一 項, 所以可以簡化為
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=800 nm SGθ只有0. 5倍的SPθ m=2 λ=630 nm SGθ約等於SPθ λ=830 nm SGθ約比SPθ高出 10% 在長波長時, accuracy χ=s/w 較高 w denote the full-width-halfλ=630 nm χP=15 RIU-1 maximum of SPR dip χG=11 RIU-1 s denote the sensitivity -1 λ=830 nm χP=83 RIU χG=48 RIU-1 在長波段時, 金屬材料的選擇(Au或Ag)則較不重要 See P 11
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!!
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