Surface plasmons are waves that propagate along the surface of a conductor. By altering the structure of a metal's surface, the properties of surface plasmons--in particular their interaction with light--can be tailored, which offers the potential for developing new types of photonic device. This could lead to miniaturized photonic circuits with length scales that are much smaller than those currently achieved. Surface plasmons are being explored for their potential in subwavelength optics, data storage, light generation, microscopy and bio-photonics.

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Surface plasmon subwavelength optics

Fundamentals of Plasmonics.- Electromagnetics of Metals.- Surface Plasmon Polaritons at Metal / Insulator Interfaces.- Excitation of Surface Plasmon Polaritons at Planar Interfaces.- Imaging Surface Plasmon Polariton Propagation.- Localized Surface Plasmons.- Electromagnetic Surface Modes at Low Frequencies.- Applications.- Plasmon Waveguides.- Transmission of Radiation Through Apertures and Films.- Enhancement of Emissive Processes and Nonlinearities.- Spectroscopy and Sensing.- Metamaterials and Imaging with Surface Plasmon Polaritons.- Concluding Remarks.

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Plasmonics: Fundamentals and Applications

The unprecedented ability of nanometallic (that is, plasmonic) structures to concentrate light into deep-subwavelength volumes has propelled their use in a vast array of nanophotonics technologies and research endeavours. Plasmonic light concentrators can elegantly interface diffraction-limited dielectric optical components with nanophotonic structures. Passive and active plasmonic devices provide new pathways to generate, guide, modulate and detect light with structures that are similar in size to state-of-the-art electronic devices. With the ability to produce highly confined optical fields, the conventional rules for light-matter interactions need to be re-examined, and researchers are venturing into new regimes of optical physics. In this review we will discuss the basic concepts behind plasmonics-enabled light concentration and manipulation, make an attempt to capture the wide range of activities and excitement in this area, and speculate on possible future directions.

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Plasmonics for extreme light concentration and manipulation.

1. Introduction 2. Theoretical foundations 3. Propagation and focusing of optical fields 4. Spatial resolution and position accuracy 5. Nanoscale optical microscopy 6. Near-field optical probes 7. Probe-sample distance control 8. Light emission and optical interaction in nanoscale environments 9. Quantum emitters 10. Dipole emission near planar interfaces 11. Photonic crystals and resonators 12. Surface plasmons 13. Forces in confined fields 14. Fluctuation-induced phenomena 15. Theoretical methods in nano-optics Appendices Index.

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Principles of nano-optics

Metals such as silver support surface plasmons: electromagnetic surface excitations localized near the surface that originate from the free electrons of the metal. Surface modes are also observed on highly conducting surfaces perforated by holes. We establish a close connection between the two, showing that electromagnetic waves in both materials are governed by an effective permittivity of the same plasma form. The size and spacing of holes can readily be controlled on all relevant length scales, which allows the creation of designer surface plasmons with almost arbitrary dispersion in frequency and in space, opening new vistas in surface plasmon optics.

https://science.sciencemag.org/content/sci/305/5685/847.full.pdf

Mimicking Surface Plasmons with Structured Surfaces

We report on the experimental observation of near-field optical effects close to Au nanoparticles using a photon scanning tunneling microscope (PSTM). Constant height operation of the PSTM allowed an unprecedented direct comparison with theoretical computations of the distribution of the optical near-field intensity. An unexpected squeezing of the optical near field due to plasmon coupling was observed above a chain of Au nanoparticles.

Squeezing the Optical Near-Field Zone by Plasmon Coupling of Metallic Nanoparticles

The implementation of optical tweezers1 at a surface opens a huge potential towards the elaboration of future lab-on-a-chip devices entirely operated with light2. The transition from conventional three-dimensional (3D) tweezers to 2D is made possible by exploiting evanescent fields bound at interfaces3,4,5. In particular, surface plasmons (SP) at metal/dielectric interfaces are expected to be excellent candidates to relax the requirements on incident power and to achieve subwavelength trapping volumes6,7. Here, we report on novel 2D SP-based optical tweezers formed by finite gold areas fabricated at a glass surface. We demonstrate that SP enable stable trapping of single dielectric beads under non-focused illumination with considerably reduced laser intensity compared with conventional optical tweezers. We show that the method can be extended to parallel trapping over any predefined pattern. Finally, we demonstrate how SP tweezers can be designed to selectively trap one type of particles out of a mixture, acting as an efficient optical sieve.

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Parallel and selective trapping in a patterned plasmonic landscape

Using the Green’s dyadic method, we investigated numerically the heat generation in gold nanoparticles when illuminated at their plasmonic resonance Two kinds of structures are discussed—colloidal-like nanoparticles and lithographic planar nanostructures—putting special emphasis on the influence of the object’s morphology at a constant metal volume The mechanism of heating is explained and discussed by mapping the heating power density inside the structures This work aims at giving an intuitive and original understanding of the relative heating efficiency of a wide set of morphologies and could stand for a basis recipe to design optimized plasmonic nanoheaters

Heat generation in plasmonic nanostructures: Influence of morphology

One‐Dimensional Plasmon Coupling by Facile Self‐Assembly of Gold Nanoparticles into Branched Chain Networks

The development of near-field optics theory is reviewed. We first recall that near-field optics is not limited to near-field microscopy. Broadly speaking, it concerns phenomena involving evanescent electromagnetic waves. The importance of such waves was ignored for a long time in optical and surface physics until the emergence of scanning near-field optical microscopes. Taking evanescent waves into account prevents the use of any simple approximation in the set of Maxwell's equations. The various theoretical approaches of near-field optics are discussed from the point of view of their ability to assess evanescent electromagnetic waves. We discuss the main results of the application of the various practical schemes which all rely on a numerical procedure. This review was received in February 1996.

https://iopscience.iop.org/article/10.1088/0034-4885/59/5/002/pdf

Christian Girard

Papers

Squeezing the Optical Near-Field Zone by Plasmon Coupling of Metallic Nanoparticles

Parallel and selective trapping in a patterned plasmonic landscape

Heat generation in plasmonic nanostructures: Influence of morphology

One‐Dimensional Plasmon Coupling by Facile Self‐Assembly of Gold Nanoparticles into Branched Chain Networks

Near-field optics theories