SURFACE PLASMON POLARITONS

1. SURFACE PLASMON POLARITONS

2. SPPs • Pioneering work of Ritchie (1957) • Propagate along the surface of a conductor • Trapped on the surface because of their interaction with the free e- • photons plasmons manipulate the original light wave properties plasmons photons

3. SPs have a combined electromagnetic wave and surface charge character Evanescent field reflects non-radiative nature of SPs, prevents power from propagating away from the surface

4. For propagation along the x-direction and homogeneity in the y direction This system allows two sets of self-consistent solutions with different polarization properties of the propagating waves.

5. For TM For TE Look for propagating wave solutions confined to the interface, with evanescent decay in the perpendicular z-direction.

6. look at TM solutions For z>0 For z< 0 For continuity of Hyand Ezat the interface A1 = A2 Confinement to the surface demands Re [ε1] < 0 if ε2 > 0 The surface waves exist only at interfaces between materials with opposite signs of the real part of their dielectric permittivities Expression for Hy has to fulfill the wave equation

7. Interaction between the surface charge density and the electromagnetic field results in the momentum of the SP mode being greater than that of a free-space photon of the same frequency.

8. Three main techniques: • Prism coupling to enhance the momentum of the incident light • Scattering from a topological defect on the surface, such as a subwavelength hole • Use of a periodic corrugation in the metal’s surface

9. The propagation length sets the upper size limit for any photonic circuit based on SPs The decay length in the dielectric material dictates the maximum height of any individual features The decay length in the metaldetermines the minimum feature size that can be used thus highlighting the need for good control of fabrication at the nanometer scale.

10. Surface plasmon band structure and periodic surfaces PBG: Using wavelength-scale periodic structures to manipulate the interaction between light and matter Periodically structured insulating and semiconducting materials Making use of SPs, metals too can be used as PBG materials a, equal to half the wavelength of the SP

11. Two SP standing wave solutions Within a bandgap, the density of SP modes is zero At the band edges, dispersion is flat and the associated density of SP modes is high

12. Kall et al. Nanoletters 2005 Sensitivity of SPR sensors: The shift per refractive index unit (RIU)

13. References • Plasmonics: Fundamentals and Applications, by Stefan Maier • Nature insight review articles: Surface Plasmon subwavelength optics, by Barnes et al. • Applied Physics Reviews- Focused Review: Plasmonics: Localization and guiding of electromagnetic energy in metal/ dielectric structures, Maier et al. • Nano Letters: Plasmonic Sensing Characteristics of Single Nanometric Holes, by Kall et al. • IEEE Journal of Selected Topics in Quantum Electronics: Plasmonics: Metal Nanostructures for Subwavelength Photonic Devices, by Stefan A. Maier • Sensors and Actuators B: Surface plasmon resonance sensors: review,Homola et al.