SPM Surface Plasmon Microscopy - Utah ECEblair/T/ece6460/papers/Lecture_19.pdf · Surface Plasmon...

Surface Plasmon MicroscopyJosh KaufmanKate WooleyKevin O’Brien

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Where we are headed

Intro – to the plasmon, the resolution, the revolution

Nostalgia – of back in the day: Kretschmann & SP’s

Getting serious – resolution enhancement

Maneuvering – around propagation lengths

Measuring up – to expectations: λsp/2

Showing off – new tricks: super/hyper-lens

Concluding – the future

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JOSH’S PART - SPMInnovative and Vital – But a bit old-fashioned

What is SPM?

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Uses Surface Plasmon Polaritons (SPPs)Allows for high contrast without sacrificing spatial resolutionSPP coupling very sensitive to optical thickness variation

“Vertical Resolution” very good – few AngstromsShift in resonance detected

Yeatman, E. Biosensors & Bioelectronics 11, 635-649 (1996)

Why use SPM?

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Fluorescence Microscopy- Need additional contrast enhancement

mechanism*

Phase Contrast Microscopy- Thickness or index contrast not enough*

Image by Steve Karl – Olympus BX Fluorescence Microscopy

Image by Asylum Research*Rothenhausler, B. & Knoll, W. Nature 332, 615-617 (1988)

Early days of plasmons

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R.H. Ritchie – 1950sTheoretical work on plasma losses by fast

electrons redefined how looked at plasmons in a thin metal foil

Condensed interactions between conduction electrons and incident electrons to 1 equation

Changed boundary conditions to have more realistic results.

Theory for SPP excitation

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Kretchmann Geometry:

Need to match momenta across surface

Grating Coupling Geometry:

Images and Equations from Lecture 10, ECE695s, Purdue University, Shalaev V.

Where we are…are you here?Questions invited








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First SPM demonstration

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1987 – Eric M. Yeatman, et. al. propose idea of Surface Plasmon Microscopy

Resonance observed from beam of given diameter –represents the result of an average in this area.

Smaller spot size = larger angular spectrum

Can reduce spot size to 10um while only halving maximum resonance

Yeatman, E. & Ash, E. Electron. Lett., 23, 1091-1092 (1987)

SPM confirmed

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Early Configuration

- Test to see where SPPs couple out

At chosen angle, only film is at resonance and excites SPPs

Rothenhausler, B. & Knoll, W. Nature 332, 615-617 (1988)

Viewing from the prism side

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Different angles excited SPPs in different materials

Material at resonance does not reflect light – EM energy fed into SPPs

Propagation length increases contrast but decreases spatial resolution

Lx = (2kx’)^-1

Rothenhausler, B. & Knoll, W. Nature 332, 615-617 (1988)

Other possibilities with SPM

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SPPs can be excited in two different layers, so one can get an idea of the unseen interface.

This is done in the near field with a photon scanning tunneling microscope

Bozhevolnyi, Smolyaninov, Zayats Phys. Rev. B 51 916-924

Bright spots form where there is roughness:

Internal interface imaging

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Bozhevolnyi, Smolyaninov, Zayats Phys. Rev. B 51 916-924

Bumps and pits cause scattering

Bumps from internal interface cause interference at external interface

Pits give bright spot, but no interference at external interface

KATE’S PART - SPMModern and Sleek – But not quite cutting edge









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Gaining Serious Resolution – In the wide-field

~2 micron resolutionKEY: Masking incident light in back focal plane for excellent image contrast

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G. Stabler, M.G. Somekh, C.W. See, J. Microscopy, Vol.214, Pt 3, June 2004, pp.328-333

High Res, Wide-field SPM

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Angle of Incidence

Back focal plane distribution and corresponding calculated intensity reflection coefficients.

(a) Back focal plane distribution on a uniform gold sample.

The horizontal direction corresponds to p-incidence and the vertical to s-incidence.

(b) Intensity reflection coefficients for p-(solid)


(a) Image of fibronectin sample obtained using the mask (black representing transmission) shown in the inset. Angular range of excitation angles of incidencefrom 30.6° to 34.6°, azimuthal angle varied from −50.5° to +50.5° from pure p-illumination.The BFP Mask – Changing polarization – Enhancing Contrast

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(b) Image of fibronectin sample, mask as for (a), but rotated through 90°. Image width approximately 110 µm.

J. Zhang, et. al. App. Phys. Lett., Vo. 85, No. 22, Nov. 2004 pg. 5451.

High Res, Wide-field SPM, Cont.

Fig.1.Back focal plane distribution obtained on grating structure; input light is horizontally polarized, parallel to the grating vector.Fig.2. The back focal plane distribution is used to form an image corresponding to an intermediate plane in the microscope, which is used to form an image on the CCD camera.

an annular mask is placed conjugate with the back focal plane to enhance contrast by blocking s-polarization.

Lateral resolution ~1-2µm

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Fig. 1.

Fig. 2.


Solid Immersion Lens (SIL) Technique

Schematic diagram of microscope system.

Inset: Ray path in aplanatic SIL used for exciting surface plasmons.

N/A~1.95

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Sample placed on Au

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Benefit of SIL – Aqueous Imaging

Image of fibronectin sample backed with water, obtained with annular mask, shown in (a), allowing incident excitation angles from 45.5° to 49.8°.

Image width approximately 70 µm.

Same sample as previous shown (in air). Contrast level between (a) and (b) as expected.

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(a) (b)

Wide-field SPM (WSPM), Oil Immersion

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(a) Image of individual fixed HaCaTs cells cultured on SPR gold coated substrate; Imaged with Differential Interference Contrast imaging (scale bar 35μm).

(e) The same individual cells as in (a) imaged with WSPR system; (scale bar 25μm).

M.M.A. Jamil, et.al.BioMed 06, IFMBE Proceedings 15, 2007

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State of the Art for WSPM ~ 500nmIn this system they combine wide-field phase confocal microscopy[1] with high resolution scanning SPR microscopy [2].Benefit of WSPM, the band like structures indicate the degree ofcell attachment to the substrate (i.e. height sensitivity).

[1] G. Stabler, M.G. Somekh, C.W. See, J. Microscopy, Vol.214, Pt 3, June 2004, pp.328-333[2] M.G. Somekh, C.W. See, J. Goh, Optics Communications, vol. 174, pp. 75-80. 2000.









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Demonstration of Defocus Technique

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MOVIE

R. Kiyan, et.al., OPTICS EXPRESS, Vol. 15, No. 7 2007 pp. 4205 4/22/2008

Maneuvering around propagation lengths – V(z) for high-resolution SPM

Defocus enhances the contrast and does not degrade lateral resolution because SPs appear to focus from a ring source.

Could improve contrast by controlling range of incident azimuthal angles, reducing s-polarized light (which does not excite SPs)

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(a) Schematic diagram showing the principal ray paths when the sample is defocused.

(b) Light polarization above the microscope objective, showing continuous variation between pure s and pure p polarization and the corresponding change in SP excitation.

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M.G. Somekh, S. Lui, T.S.Velinov, and C.W. See, Opt. Lett. Vol. 25, No.11 823-825 (2000)

Defocus Technique, V(z)26

4/22/2008M.G. Somekh, S. Lui, T.S.Velinov, and C.W. See, Opt. Lett. Vol. 25, No.11 823-825 (2000)

V(z) Interferometric Technique27

Fig. 1. Schematic diagram of the scanning heterodyne interferometer used in the experiments.

Fig. 2. Diagram showing different polarization components in the field that is reflected in the back focal plane of the microscope objective.

Fig. 1 Fig. 2

M.G. Somekh, S. Lui, T.S.Velinov, and C.W. See, Opt. Lett. Vol. 25, No.11 823-825 (2000)

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V(z) Summary28

SPM imaging with lateral resolution limited by diffraction rather than propagation distance

Advantage over Optical: SP’s are sensitive to dielectric properties, and sensitivity > reflection/interference techniques

But, V(z) is still a scanning technique. Wide-field has not been demonstrated

M.G. Somekh, S Lui, T.S.Velinov, and C.W. See, App. Opt. 39, No. 34 pg 6279-6287(Dec 2000) M.G. Somekh, S Lui, T.S.Velinov, and C.W. See, Opt. Lett. 25, 823-825 (2000)

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KEVIN’S PART - SPMNovel and State of the Art - But is it the future?









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Surface Plasmon Polariton Enhanced Optical Microscopy

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SPP used to enhance resolution instead of contrast!Resolution of optical microscope is around:

near Plasmons reflected off edges of liquid drop through total internal reflection.

n2/λ

Smolyaninov et al, PRL (2005)

Plasmonic dispersion relation assuminglow losses. (Drude model)


lightsp λλ < spω

Surface Plasmon Polariton Enhanced Optical Microscopy

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Nanoholes on square of gold foil “emit” SPPs when illuminated.

Parabolic glycerin drop used like a mirror to guide and magnify SPPs.

Points on sample mapped to magnified points on drop.

Points are magnified enough that separations are large enough to be seen by an optical microscope.

Plasmons are viewed in an optical microscope when they scatter off of surface roughness and become propagating waves.

Smolyaninov and Davis, Phys Rev B (2005)


Experiment:

Simulation:


Resolved group of holes.

SEM Image:Nanohole array as viewed in liquid drop:

Nanoholes:100 nm diameter 40nm separation.

30um

Application of SPP Enhanced Optical Microscopy

Example: Imaging of a T4 phage virus with 502 nm light.Nanohole array provides the SPPs for imaging.Glycerin lens magnifies. Optical microscope picks up light emitted by plasmons after magnification.Virus looks as if viewed with a 50 nm resolution optical microscope.

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~200nm

SEM Image

~80-100 nmSmolyaninov et al, PRL (2005)

~50 nm resolution

Virus as seen in liquid drop

Foil grid and glycerin drop

Digital Resolution Enhancement

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~70 nm resolution not good enough for biological applicationsWith a known PSF, can get higher resolution by deconvolution.“Laplacian filter matrix deconvolution”Resolution of ~30 nm obtained

Smolyaninov et al, Appl. Phys. B (2006)

Deconvolution

Resolution=64nm Resolution=32nm

Review of Imaging Theory:

⊗ =Stars Telescope PSF

Image you see in your telescope.

Another Approach to SPP Enhanced Microscopy

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Can also use Bragg mirror to magnify SPP. Bragg mirror built from closely spaced gold protrusions.Photonic crystal for plasmons.SPPs imaged by leakage radiation microscopy (LRM)Resolution is on the order of:

Plasmon wavelength so much smaller than structure that geometric optics can be used.Magnification = F2/F1

nma SP 3902/ =≅ λ2/SPλ

Drezet et al, Optics Letters (2007)

SEM Image of Reflector

“Plasmonic Crystal”

Another Approach to SPP Enhanced Microscopy continued …

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Advantage: More controlled structure than glycerin drop.Disadvantages: 1D and must place sample very precisely at focus.Not as useful as liquid drop method for imaging applications.

Drezet et al, Optics Letters (2007)

Gold protrusion(s) at center of F1

nmSP 3902/ =λ 2/400 SPnm λ≅









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Super-Resolution Review

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Zubin J, Alekseyev L, Narimanov E., Optics Express (2006)Idea for layout from Lecture 15,

ECE695s, Purdue University, Shalaev V.

Regular lens:Evanescent waves lost.

Superlens:Evanescent waves amplified but still decay.

Hyperlens:Converts evanescent waves into propagating waves which do not interfere with other propagating waves.

The Role of SPPs in Super and Hyperlenses

SPPs used to amplify evanescent waves in Pendry’s silver slab superlens.SPPs are generated by the p-polarized incoming light and couple with the evanescent field emerging from the object and amplify it.

Pendry, PRL (2000)In visible frequency hyperlens designs SPPs couple the light between the layers.

Liu et al, Science (2007), Smolyaninov et al, Science (2007)

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Smolyaninov et al, Science (2007)

Liu et al, Science (2007)

Idea: Pendry, PRL (2000)Graphic: Smith D., Science (2005)

Far Field Superlens Theory

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Silver slab based super-lens + scattering structure to enable far field imaging.Combines super-lensing and far-field imaging capability.

Lee, Zhang et al, Solid State Electronics (2008)

Liu, Zhang et al, Nanoletters (2007)

Durant et al, J. Opt. Soc. Am. B (2006)

The physics behind it: The design:Surface for specimen

Far Field Superlens continued …

s-polarization used to obtain image from propagating waves.

s-polarization does not excite plasmons so it can pass through the silver with smaller losses.

s+p polarizations used to obtain image from evanescent waves.

Images combined for a complete picture of the object.

<70 nm resolution at a wavelength of 377 nm.

Lens is flat and easy to make!

Can be generalized to produce 2D magnification using a more complex scattering structure.

Silver slab is lossy => resolution limit

If ti h t

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Liu, Zhang et al, Nanoletters (2007)

Benefits:

Function:

Downsides:









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Future of Super-resolution Imaging

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Resolution of SPP enhanced optical lens is higher than current hyperlenses or far field superlenses.This could easily change in the future.All types of Super-resolution imaging have important applications in biology and lithography.Flat hyperlens and Far field superlens (FSL) would be the most convenient for imaging larger areas.

Begin Hidden Backup Slides

All slides after this will be hidden during the presentation and can be used to answer particularly difficult questions.

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Hyperlens Theory

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Based on anisotropic metamaterialsWave vectors can become arbitrarily large.

Zubin J, Alekseyev L, Narimanov E. , Optics Express (2006)

Zubin J, Alekseyev L, Narimanov E. , Optics Express (2006)

1D Hyperlens Experiment

~70 nm resolution obtained when hyperlens is illuminated by 495 nm light.Plasmons in anisotropic dispersion propagate radially and spread far enough to be imaged with an optical microscope.Propagate when n1*d1=-n2*d2 => radial propagation.

Magnification based SPM 4/22/08

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SEM of Hyperlens Optical Image of Hyperlens

Smolyaninov et al, Science (2007)

PMMA rings on gold

1D Hyperlens Experiment

130 nm resolution obtained with ~364 nm light.Magnification only occurs in one directionSPPs used to large k light between metallic layers.

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Far Field Superlens: Evanescent Band Shifting

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Demonstrates how a FSL operates by shifting a selected evanescent band to the propagating band.Depending on the OTF of the FSL the shifting evanescent band can be changed. This gives different spatial information about the object.

Lee, Zhang et al, Solid State Electronics (2008)

SPP Enhanced Optical Microscopy

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air glycerin

)( goldglycerinsp −ω

)( goldairsp −ω

Operating frequency

ω

k

air glycerin

)( goldglycerinsp −ω

)( goldairsp −ωOperating frequency

ω

k

SPM Surface Plasmon Microscopy - Utah ECEblair/T/ece6460/papers/Lecture_19.pdf · Surface Plasmon...

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Transcript of SPM Surface Plasmon Microscopy - Utah ECEblair/T/ece6460/papers/Lecture_19.pdf · Surface Plasmon...