Magnificent Optical Properties of Noble Metal Spheres, Rods and Holes Peter Andersen and Kathy Rowlen Department of Chemistry and Biochemistry University of Colorado, Boulder Funded by the National Science Foundation

1970’s  surface enhanced Raman scattering 1980’s  10 6 enhancement of Raman scattering 1980’s  second harmonic generation 1997  enhancement of Raman scattering 2000  10 6 enhancement of fluorescence in nanorods 2001  surface plasmon optics Surface Plasmons: coherent oscillations of electron density at metal/dielectric interface Enhanced Optical Processes from Nanometric Noble Metal Particles

Enhanced Optical Transmission Ebbesen et al. “Extraordinary Optical Transmission Through Sub-Wavelength Hole Arrays” Nature, 1998, 391,

Saloman et al. Phys. Rev. Lett. 2001, 86(6), nm Ag film v.d. onto quartz focused ion beam lithography 150 nm holes 600 nm to micron spacing

Ghaemi et al. Phys. Rev. B 1998, 58(11), 6779

Thio et al., J. Opt. Soc. Am. B., 1999, 16(10), 1743 Measured Near-Field Distribution Closest to simulated c (previous), hole d = 500 nm

Ebbesen et al. Nature 1998, 391, nm thick Ag 150 nm holes 900 nm spacing Transmission efficiency = fraction of light transmitted/ fraction of surface area holes = 2. More than twice the light that impinges on the holes is transmitted through the film!

Ebbesen et al. Nature 1998, 391,667 Hole spacing determines peak position Peak position independent of hole d Independent of metal (Ag, Cr, Au) Must be metal (Ge doesn’t work)

T scales with d 2, independent of versus (d/ ) 4 for Bethe sub- aperture =500 nm

Not cavity resonance since peak position (in spectrum) does not significantly depend on hole dimensions Not waveguiding because film thickness too small (200 nm) Surface plasmon tunneling? Surface plasmon scattering? Enhancement / Transport Mechanism?

For a surface that can support a surface plasmon, the wave vector, k sp is: The difference between the in-plane wave vector of light, k i, and the surface plasmon wave vector, k sp, can be compensated for by diffraction on periodic surface structure:

Grupp et al., Appl. Phys. Lett. 2000, 77(11), 1569 Ag Ag/Ni Ni

Grupp et al., Appl. Phys. Lett. 2000, 77(11), 1569 Transmission relatively independent of wall metal

Sonnichsen et al., Appl. Phys. Lett. 2000, 76(2), 140 Further evidence for surface plasmon involvement

Sonnichsen et al., Appl. Phys. Lett. 2000, 76(2), 140

Saloman et al. Phys. Rev. Lett. 2001, 86(6), 1110 Left: Calculated near-field transmission intensity [(c) = 300 d, 900 nm a, 800 nm ] Calculated intensity enhancement near hole edge ~ 500x 15 nm above 100 nm above

Thio et al., Physica B, 2000, 279, 90

Grupp et al. Adv. Matr. 1999, 11(10), 860

Thio et al., Physica B, 2000, 279, 90 Surface Plasmon Activated Devices

Grupp et al. Adv. Matr. 1999, 11(10), 860 Transmission through single hole with array of dimples Single hole in smooth surface

Thio, Lezec, Ebbesen Physica B, 2000, 279, 90 For coherent 670 nm light T is 60x greater than typical NSOM tapered fiber with 200 nm aperture

Applications, Applications, Applications! Reflection mode? SERS at edges? Field in channel?

Surface Plasmon Optics: use SP’s for manipulation of optical fields SP lenses, mirrors and flashlights (e.g., Smolynaninov et al. Phys. Rev. B. 1997, 56(3) )

Optical Enhancement via Surface Plasmon Coupling h Field enhanced detection region Light harvesting indentations Surface plasmon mirror Transmission channel Surface plasmon lense

Si substrate Spin coat substrate with PMMA resist Expose to electron beam Develop in MIBK/IPA Metalize by vapor deposition Electron-Beam Nanolithography (Peter Andersen)

Reflection Grating Behavior

First Attempt: Top-View AFM

AFM Micrograph of Second Attempt!

target a o 450 nm measured a o 450 nm Grating Constant (a o )

Lens Pinhole Au Mirror Nd:YAG Laser  = / 2sin  Photolithography (Michele Jacobson)

To be continued…..