Plasmonics

Plasmonics is a growing field in science & technology that is devoted to the study and applications of a wide variety fo phenomena that originates from the unusual optical properties of nano-sized metals.

While "bulk" metals like silver and gold have shiny reflective surfaces, suspensions of tiny particles made with these chemical elements have very different optical properties.

The vastly distinct colours exhibited by metal nanoparticles arise due to the excitation of localised surface plasmon resonances.

Surface plasmons are coherent (in phase) collective oscillations of electrons with respect to the lattices of atoms making up metal. Plasmons characterised by the appearance of surface charges that oscillate at optical frequencies. These surface-charge oscillations lead to enhanced electromagnetic fields, which are strongly localised at metal surfaces and interfaces.

Self-Assembly of Plasmonic Near-Perfect Absorbers of Light: The Effect of Particle Size

Structures capable of perfect light absorption promise technological advancements in varied applications, including sensing, optoelectronics, and photocatalysis. While it is possible to realize such structures by placing a monolayer of metal nanostructures above a reflecting surface, there remains limited studies on what effect particle size plays on their capacity to absorb light. Here, we fabricate near-perfect absorbers using colloidal Au nanoparticles, via their electrostatic self-assembly on a TiO2 film supported by a gold mirror. This method enables the control of interparticle spacing, thus minimizing reflection to achieve optimal absorption. Slightly altering the nanoparticle size in these structures reveals significant changes in the spectral separation of hybrid optical modes. We rationalize this observation by interpreting data with a coupled-mode theory that provides a thorough basis for creating functional absorbers using complex colloids and outlines the key considerations for achieving a broadened spectral response.

Plasmonic Near‐Complete Optical Absorption and Its Applications

This review paper reports recent progress on the development of metasurfaces and thin film structures that produce strong absorption bands in the visible and longer wavelength regions of the electromagnetic spectrum, due in part to the excitation of plasmonic resonances.

Plasmonic edge states

By using our "Eigenmode" model, we have theoretically predicted, and experimentally demonstrated how a collection of Gold nanorods can focus incident energy into an extremely small volume. The full story can be found here

The Dark side of plasmonics

Not all that glitters is gold! And not all spatial arrangements of Gold nanoparticles glitter... We show from theory, nanofabrication and spectroscopy, how certain arrangements of metal nanostructures posses "dark" plasmon modes. These modes can trap light energy for applications in energy conversion. More details here

Symmetry

Symmetry plays a significant role in nature. It also controls how artificial structures interact with light. Using our "eigenmode" theory, we demonstrated how the tools of group theory can be used for designing metal nanostructures. Full story here

ColloquiumLocalized surface plasmons are collective modes of the conduction electrons excited by light in metal nanoparticles. Although plasmons have been known for some time, their use for controlling light at the nanometer scale only became possible with developments in near field optics. To model interactions between such collective modes is a complex problem that requires heavy computation. In this Colloquium an algebraic model for plasmons is discussed that elucidates the physics of these collective modes and their interactions.

Plasmonics by design: design principles to structure–function relationships with assemblies of metal nanoparticles

We present an overview on how a simple and analytical theoretical method, namely the Electrostatic Eigenmode Method (EEM), can be used for designing or interpreting the phenomena that results from plasmon coupling. This presentation is complemented with select examples on our successful application of this theory to experiments highlighting the physical insights obtained.

This article is part of the themed collection: Emerging Investigators