Optics on a Nanoscale Using Polaritonic and Plasmonic MaterialsOptics on a Nanoscale Using Polaritonic and Plasmonic Materials(NSF NIRT 0709323)(NSF NIRT 0709323)

Andrey ChabanovAndrey Chabanov11, Federico Capasso, Federico Capasso22, Vinothan Manoharan, Vinothan Manoharan22, Michael Spencer, Michael Spencer33, Gennady Shvets, Gennady Shvets44, Christian Zorman, Christian Zorman55

11University of Texas-San Antonio, University of Texas-San Antonio, 22Harvard University, Harvard University, 33Cornell University, Cornell University, 44University of Texas-Austin, University of Texas-Austin, 55Case Western Reserve University Case Western Reserve University

Motivation and GoalsMotivation and Goals: Coupling Optical Energy to Nanoscale: Coupling Optical Energy to Nanoscale

Light diffraction prevents confinement of light in regions smaller than half a laser wavelength thus impeding the development of future nanophotonic devices and limiting future nanoimaging applications. Surface polaritons, on the other hand, can have wavelengths that are orders of magnitude shorter than in vacuum. Thus plasmonic/ polaritonic components may enable us to achieve unprecedented focusing of optical energy that can address the needs of nanophotonics, nanomanufacturing, NEMS, nanoscale thermal source development, and nanofluidics.

The Key Challenges in coupling optical energy to nanoscale are addressed by the NIRT:

(i) Creating nanoscale polariton-based building blocks of metamaterials/ metafluids with controlled optical properties;

(ii) Accomplishing strongly subwavelength, nanoscale resolution by designing a mid-infrared polariton-based superlens integrated with a scattering NSOM;

(iii) Demonstration of extraordinary optical energy focusing on a nanoscale through the excitation and guiding of surface polaritons.

The plasmonic/ polaritonic components aimed by the NIRT are to lead to in vivo imaging of nanoscale biological objects and revolutionize label-free detection of biological and chemical substances.

Artificial Plasmonic Molecules-based metafluidsArtificial Plasmonic Molecules-based metafluidsLiquid metamaterials, or metafluids, are based on clusters of metallic nanoparticles, or Artificial Plasmonic Molecules (APMs), which exhibit strong electric and magnetic responses. Colloidal solutions of plasmonic nanoclusters can act as an optical medium with very large, small, or even negative effective permittivity and substantial effective magnetic permeability in the visible and near-infrared spectral bands. The properties of the metafluids can be controlled by an external signal.

130-nm SiO2 core, 25-nm thick gold shell 170-nm SiO2 core, 25-nm thick gold shell

180-nm diameter nanoshell trimer 220-nm diameter nanoshell trimer

Silica cores are synthesized and functionalized with a silane linker

Gold nanoparticles are self-assembled onto the surface and gold shells with controllable shell thickness are created by electroless deposition Gold nanoshells are assembled into trimers using capillary-force clustering or DNA-mediated adhesion

Single nanoshell absorption spectra of particles are measured in air on a glass substrate

Seeing through water: Seeing through water: in vivoin vivo imaging of small imaging of small biological objectsbiological objects

Subsurface imaging through a SiC-superlens microstructureSubsurface imaging through a SiC-superlens microstructure

nanofluidic channel

SiC

PDMS

NSOM tip

SiC film

PDMS

water

Resolution of λ/20 for 2-D objects (holes)

Increased range of frequencies for imaging amplitude or phase

Higher resolution with phase imaging less sensitive to topography

Bonding of SiC membranes to PDMS holder demonstrated

Fluid delivery system (microfluidic channels connect to the nanofluidic sub-surface channel) developed and tested

Presently working on the inscription of small objects (holes, metal discs, etc.) at the bottom of the nanofluidic channel

λ=9.27 µm λ=10.85 µm λ=10.62 µm λ=11.03 µm

Amplitude image Phase image

SEM image500 nm middle holes

continuous silver wires control eff

80 nm

20 nm

320 nm80 nm

50 nm

250 nm

“cut” silver wires control eff

impedance matching

re = re = -1

Perfect impedance matched negative index material absorberPerfect impedance matched negative index material absorber

This structure is subwavelength (period ~

λ/5 ) and operates in ε = μ = -1 regime

Peak absorption varies between 100% and 75% for the 90-deg full-angle spread

Absorption peak is spectrally narrow (10%) and widely tunable (1300nm < λ < 1600nm)

Using high melting temperature metals (e.g. tungsten) shifts the wavelength to λ = 2.4 μm and enables thermovoltaic applications

Using SiC shifts resonances to λ = 11 μm night-vision applications