Plasmons Used in Optical Communications

When ripples in the fluid-like free electrons in conducting metals form oscillations, they can act like virtual particles and are called “plasmons”, a category of quasiparticles. Controlling plasmons which interact with light allows fast and efficient modulation of light based communications.

What is a plasmon? – []

A plasmon is a collective excitation of the electronic “fluid” in a piece of conducting material, like ripples on the surface of a pond are a collective mode of the water molecules of the liquid. The simile here isn’t too far off, because like water, the electronic fluid in a metal is pretty close to incompressible. If you push down on the surface of a pond somewhere with a float, the density of the water doesn’t change; instead the water elsewhere is displaced, because the water molecules have finite volume and push each other out of the way. The electronic fluid acts similarly, not because of any finite size or even the Coulomb repulsion of the electrons, but mostly because of the Pauli exclusion principle, which tends to keep the electrons out of each others’ way.

Plasmonics: revolutionizing light-based technologies via electron oscillations in metals – []

Concentrating light

Plasmonics demonstrates how light can be guided along metal surfaces or within nanometer-thick metal films. It works like this: on an atomic level, metal crystals have a very organized lattice structure. The lattice contains free electrons, not closely associated with the metal atoms, that interact with the light that hits them.

These free electrons collectively start to oscillate with respect to the fixed position of positively charged nuclei in the metal lattice. Like the density of air molecules in a sound wave, the electron density fluctuates in the metal lattice as a plasmon wave.

Visible light, which has a wavelength of approximately half a micrometer, can thus be concentrated by a factor of nearly 100 to travel through metal films just a few nanometers (nm) thick. That’s 1,000 times smaller than a human hair. The new mixed light-electron-wave-state empowers intense light-matter interactions with unprecedented optical properties.

‘Plasmonic’ material could bring ultrafast all-optical communications – []

Researchers have created a new “plasmonic oxide material” that could make possible devices for optical communications that are at least 10 times faster than conventional technologies.

In optical communications, laser pulses are used to transmit information along fiber-optic cables for telephone service, the Internet and cable television.

Researchers at Purdue University have shown how an optical material made of aluminum-doped zinc oxide (AZO) is able to modulate – or change – how much light is reflected by 40 percent while requiring less power than other “all-optical” semiconductor devices.

Liquid Crystal Phonon Lenses

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