A.V. Krasavin

Active plasmonics: Controlling signals in Au/Ga waveguide using nanoscale structural transformations

We have developed a concept for active plasmonics that exploits nanoscale structural transformations which is supported by rigorous numerical analysis. We show that surface plasmon-polariton signals in a metal-on-dielectric waveguide, containing a gallium section a few microns long, can be effectively controlled by switching the structural phase of gallium. The switching may be achieved by either changing the waveguide temperature or by external optical excitation. The signal modulation depth could exceed 80% and switching times are expected to be in the picosecond–microsecond time scale.

Broken time reversal of light interaction with planar chiral nanostructures.

We report unambiguous experimental evidence of broken time-reversal symmetry for the interaction of light with an artificial nonmagnetic material. Polarized color images of planar chiral gold-on-silicon nanostructures consisting of arrays of gammadions show intriguing and unusual symmetry: structures, which are geometrically mirror images, lose their mirror symmetry in polarized light. The symmetry of images can be described only in terms of antisymmetry (black-and-white symmetry) appropriate to a time-odd process. The effect results from a transverse chiral nonlocal electromagnetic response of the structure and has some striking resemblance with the expected features of light scattering on anyon matter.

High-contrast modulation of light with light by control of surface plasmon polariton wave coupling

We have demonstrated a mechanism for modulating light with light by controlling the efficiency with which light is coupled into a plasmon polariton wave. An optical fluence of 15mJ∕cm2 in the control channel is sufficient to achieve nearly a ten-fold intensity modulation of the signal beam reflected from a Glass ∕MgF2∕Ga structure. The mechanism depends on a nanoscale light-induced structural transformation in the gallium layer and has transient switching times of the order of a few tens of nanoseconds. It offers high modulation contrast for signals in the visible and near infrared spectral ranges.

Active control of surface plasmon–polariton waves

We outline a new concept for active plasmonics that exploits light-induced nanoscale structural transformations in the waveguide material. The concept is illustrated by numerical modelling and test experiments on a gallium–dielectric interface. We also discuss other possible implementations of the concept such as an electro-plasmon modulator, a plasmon detector and a switch that controls one plasmon wave with another.

Polarization conversion and “focusing” of light propagating through a small chiral hole in a metallic screen

Propagation of light through a thin flat metallic screen containing a hole of twisted shape is sensitive to whether the incident wave is left or right circularly polarized. The transmitted light accrues a component with handedness opposite to the incident wave. The efficiency of polarization conversion depends on the mutual direction of the hole’s twist and the incident light’s wave polarization handedness and peaks at a wavelength close to the hole overall size. We also observed a strong transmitted field concentration at the center of the chiral hole when the handedness of the chiral hole and the wave’s polarization state are the same.

Extraordinary properties of light transmission through a small chiral hole in a metallic screen

The true three-dimensional finite element numerical solution of Maxwells equations shows that the propagation of light through a thin flat free-standing metallic screen containing a hole of twisted shape is sensitive to whether the incident wave is left or right circularly polarized. The intensity map and polarization state of light are dramatically changed depending on the mutual direction of the holes twist and the incident lights wave polarization handedness. We also observed a strong concentration of the transmitted field at the centre of the chiral hole when light in the object plane rotates against the twist of the investigated gammadion type structure.

Gallium/aluminum nanocomposite material for nonlinear optics and nonlinear plasmonics

We report on a new type of composite metallic structure for nonlinear optics and nonlinear plasmonics, created by grain boundary penetration of gallium into an aluminum film. These composite films form mirrorlike interfaces with silica and show an exceptionally broadband phase-transition-based nonlinear response to optical excitation.

Chapter 4 – Active plasmonics

Publisher Summary This chapter discusses various aspects of the concept of active plasmonics. It numerically analyses the performance of different components of the generic active plasmonic switch. The coupling and decoupling of light to and from surface plasmon–polariton (SPP) waves using gratings are explained in the chapter. The angle at which an output light beam is decoupled is determined by the period of the decoupling grating. The efficiency with which light can be coupled to and decoupled from SPP waves by gratings on metal/dielectric waveguides depends strongly on the geometric profiles of the gratings. Detailed numerical investigations of the plasmonic switching device have been conducted for the case where SPP waves are incident normally on the gold/gallium boundary in two-dimensional simulations. The experimental tests designed to validate the active plasmonics concept, and to determine the energy requirements and response characteristics for plasmonic switching in gallium through a nanoscale light-induced structural transformation, is also elaborated in the chapter.

Gallium/aluminium nano-composite for nonlinear-optical and plasmonic switching applications

Placing a small drop of gallium on an aluminium film starts a nanoscale grain boundary penetration process that creates a robust, highly nonlinear, switchable mirror suitable for plasmonic and nonlinear optical applications.

Ga-Al and Ga-Ag nano-structured films for active plasmonics applications

Surface plasmon-polariton waves, promising information carriers for highly integrated photonic devices, can be controlled through nanoscale structural transformations in the waveguide material. Here we propose and investigate new nano-structured material suitable for this application.