Super-Diffraction Limited Wide Field Imaging and Microfabrication Based on Plasmonics

Transcription

1 Super-Diffraction Limited Wide Field Imaging and Microfabrication Based on Plasmonics Peter T. C. So, Yang-Hyo Kim, Euiheon Chung, Wai Teng Tang, Xihua Wang, Erramilli Shyamsunder, Colin J. R. Sheppard MIT, Boston University, National University of Singapore

2 Overview Background Total internal reflection Motivation Theory Surface Plasmon and Photon coupling Experimental Setup Experiment & Results Future work 2

3 Total internal reflection (TIR) z Ez k z z ~ e x [ ] E = E0 exp i ( kxx + kzz ωt ) ( 3

4 TIR imaging z x k High n i( kx ωt) 2 2 = = Ix ( ) Ee E Uniform excitation ) i( 2 i( kx ωt φ) i( kx ωt) Ix ( x ) = Ee + + Ee Ee 2 = 2 E [1 + cos(2 kx)] φ)] Standing wave excitation 2 (Chung et al., Opt. Lett., 2006) 4

5 TIR lithography z x Photosensitive material Ix ( ) = 2 E 2 [1+ cos(2 kx)] z p k p π θ = 2 n sin λ = λ /(2nsin θ ) x (Ecoffet et al., Adv. Mater., 1998) p: period of the pattern, n: refractive index 5

6 Motivation Total internal reflection (TIR) of light Interference Surface Plasmon of Two Resonance Evanescent (SPR) Waves Imaging Lithography Strong field enhancement High S/N ratio Shorter Wavelength Higher Resolution 6

7 Field enhancement by SPR E output air z Ez k z z ~ e metal x E input θ 0 glass E E output input = 20 ~ 200!! (Raether, Surface Plasmons on Smooth and Rough Surfaces and on Gratings.1988, Berlin: Springer) 7

8 Higher resolution by SPR (I) k sp ε 2 ( kphoton ) ε x 1 air metal a ε 0 glass θ 0 ω ksp = ( kphoton ) x = ε0 sin θ0 + mg ( g = 2 π / a) c k: wavevector, a: grating period, m: diffraction order, ε: dielectric constant 8

9 Higher resolution by SPR (II) E p = hω ( h = h/2 π ) = hk ω light line TIR TIR + Grating 1/2 ω εε 1 2 ksurface plasmon = c ε1+ ε2 ω ( kphoton ) x = ε0 sinθ0 + mg c k 0 k TIR k TIR + grating k x 532 nm 104 nm!! k: wavevector, a: grating period, m: diffraction order, ε: dielectric constant (Raether, Surface Plasmons on Smooth and Rough Surfaces and on Gratings. 1988, Berlin: Springer) 9

10 Experimental setup 10

11 SPR field enhancement experiment (I) Bead SiOx (5nm) Au (40 nm) Glass (n=1.522) SPR sample TIR sample Fluorescent beads (d = 40nm) SPR angle (~45 ) Incident power (7.8 mw) N = 48 samples 11

12 SPR field enhancement experiment (II) 12 μm Intensity (A.U.) 12 μm (a) SPR (P pol) (b) SPR (S pol) (c) TIR (P pol) (d) TIR (S pol) 12

13 SPR field enhancement experiment (III) 500 Intensity from 48 beads 400 Intenstiy (A.U.) SPR(P pol) SPR(S pol) TIR(P pol) TIR(S pol) P-value<

14 TIR Lithography experiment (I) Congo Red (n=1.9) (Ohdaira, Y., et al., Colloids Surf. A, 2006) Glass (n=1.522) S-polarization P-polarization Spin coating Congo Red solution with deionized water Exposure (800 mw/cm 2 S-polarization for 30 min) Exposure (2000 mw/cm 2 P-polarization for 10 min) 14

15 TIR Lithography experiment (II) (Ohdaira, Y., et al., Colloids Surf. A, 2006) (a) S-polarization 2.00 μm (b) P-polarization (Kim, Y., et al., In preparation) μm 15

16 Summary Interference of two surface plasmon waves for imaging and lithography. 1) Strong field enhancement (high S/N ratio) 2) Longer wave vector (higher resolution) The results: 1) SPR strong field enhancement (bead imaging) 2) P-polarization Congo Red lithography is possible. 16

17 Future Work Make a corrugated gold coated glass sample The high resolution (~50 nm) imaging and lithography with the sample 17

18 Thank you! & Questions? 18

19 Future Work (II) ~200 nm ~80 nm (Maier, Plasmonics: Fundamentals and Applications. 2007, Springer) 19

20 Future Work (II) 0.7 SP dispersion relation of glass-au-air nm Air Au Glass W (10 15 Hz) Surface plasmon light line TIR TIR+grating nm excitation k x (10 8 /m) 508 nm 105 nm 20

21 Future Work (II) 0.7 SP dispersion relation of glass-au-congo Red 0.6 Congo Red nm Au Glass W (10 15 Hz) Surface plasmon light line TIR TIR+grating nm excitation k x (10 8 /m) 513 nm 104 nm 21

22 Resolution I ~ 0.2λ ~ 0.2λ ( ) ( ) h x + + h x NA NA r = 0.4 λ < 0.61 x λ ( NA) ( NA) (MIT Optics lecture note) 22

23 Resolution II Rayleigh resolution criterion (imaging) 0.61 λ λ = 0.61 NA n sin θ Optical Projection Lithography resolution λ λ κ1 = κ1 NA n sinθ Objective lens θ Numerical Aperture NA= n sin θ Κ1: constant for a specific lithographic process (Chiu at al., IBM Journal of Research and Development, ) 23

24 Polarization E i E r k r E i E r k r B i k i B r B i k i B r Interface E t kt Interface E t B t B t k t S-polarization P-polarization

25 Linear polarizer (Collett, Edward. Field Guide to Polarization, SPIE Field Guides vol. FG05, SPIE (2005)) 25

26 Surface Plasmon-Coupled Emission (E. Chung, thesis, MIT, 2007) 26

27 AFM Deflection of the cantilever is measured. Feedback mechanism prevent the collision of the tip and the surface. Humphris at al., A mechanical microscope: High-speed atomic force microscopy, Applied Physics Letters 86, (2005). 27

28 Piezoelectric effect The unit cell of crystal silicon dioxide deformation (+) (-) (-) A pushing force: (aka: compression) ( + (+) A pulling force: (aka: tension) 28

29 Fluorescence ( 29

30 Congo Red (Ohdaira, Y., et al., Colloids Surf. A, 2006) ( 30

31 Spin coating Centrifugal force spread a fluid resin. 31

32 CCD & CMOS Uniform image quality High fill factor Low noise Simple Cost less Consume less power Many function Integration on one chip 32

33 t-test Population Mean: µ Standard deviation: σ Sample Mean: X Standard deviation: S Number of samples: n T = X µ S/ n P value : the provability that X µ when random sampling small P value : we can trust X as µ with higher probability. 33

34 Original experimental setup 34

35 Fringe spacing ( ) x = f / M nsinθ 2 TB 1 p(x 1)= 2 f f λ x TB 1 M f2 1 λ p= sinθ 2n (E. Chung, thesis, MIT, 2007) 35

36 SPR field enhancement experiment (IV) (E. Chung, thesis, MIT, 2007) 36

37 ω Surface plasmon and photon coupling (I) light line TIR ω light line Grating k 0 k TIR 1/2 ω εε 1 2 ksurface plasmon = c ε1+ ε2 ω ( k photon ) x = ε0 sinθ0 c ' k x k 0 k grating 1/2 ω εε 1 2 ksurface plasmon = c ε1+ ε2 ω ( k ) = ε sinθ + c photon x 0 0 m g ' k x k: wavevector, a: grating period, m: diffraction order, ε: dielectric constant (Raether, Surface Plasmons on Smooth and Rough Surfaces and on Gratings. 1988, Berlin: Springer) 37

38 ω Surface plasmon and photon coupling (II) light line TIR k 0 k TIR 1/ 2 ω εε 1 2 k = surface plasmon c ε1 + ε2 ω ( k photon ) x = ε0 sinθ0 c ' k x k: wavevector, a: grating period, m: diffraction order, ε: dielectric constant (Raether, Surface Plasmons on Smooth and Rough Surfaces and on Gratings. 1988, Berlin: Springer) 38

39 Wave vector change by grating A a D θ i B C θ m AB CD = a(sinθ sin θ ) = mλ m i 2π mλ 2π ( kout ) x ( kin ) x = k0(sinθm sin θi ) = = m mg λ a = a (Hecht, OPTICS, 2001, Addison Wesley) 39

40 Wavelength dependence of various materials (Hecht, Optics. 2002, Addison-Wesley) 40

41 Dispersion in atom (Hecht, Optics. 2002, Addison-Wesley) 41

42 Dispersion relation of SP (I) (Raether, Surface Plasmons on Smooth and Rough Surfaces and on Gratings.1988, Berlin: Springer) 42

43 Dispersion relation of SP (II) (Raether, Surface Plasmons on Smooth and Rough Surfaces and on Gratings.1988, Berlin: Springer) 43

44 Dispersion relation of SP (III) (Raether, Surface Plasmons on Smooth and Rough Surfaces and on Gratings.1988, Berlin: Springer) 44

45 Dielectric function of gold (Raether, Surface Plasmons on Smooth and Rough Surfaces and on Gratings.1988, Berlin: Springer) 45

46 Source of Noise in Optical Detectors (1) Optical shot noise (N s ) inherent noise in counting a finite number of photons per unit time (2) Dark current noise (N d ) thermally induced firing of the detector (3) Johnson noise (N J ) thermally induced current fluctuation in the load resistor Since the noises are uncorrelated, the different sources of noise add in quadrature 2 2 S 2 d N N + N + N 2 J (MIT Optics lecture note)