Synopsis: Proactive metamaterials

Structurally engineered electromagnetic materials have now been made from active elements, expanding the range of possible optical effects in such so-called “metamaterials.”
Synopsis figure
Credit: Adapted from M. Wegener and S. Linden, Physics 2, 3 (2009)

When fabricated with structural patterning such as holes or twists, normal materials can acquire completely new electromagnetic properties, including perfect focusing (superlensing) and cloaking. These “metamaterials” are generally constructed from passive metals and insulators, deriving their unusual properties from structure rather than intrinsic composition. But as Alexander Katko, Shi Gu, John P. Barrett, Bogdan-Ioan Popa, and Steven Cummer of Duke University, and Gennady Shvets of the University of Texas at Austin, both in the US, report in Physical Review Letters, an entirely new set of possibilities emerges when metamaterials are made from active nonlinear elements whose inherent properties can be adjusted by external control or react dynamically to incident fields.

One basic building block of metamaterials is the split-ring resonator (SRR), a pair of notched annular metal rings. These are then assembled in 2D or 3D arrays to create the structured material with desired properties. Katko et al. combine the split in the ring with varactor diodes, which act as a combination of a diode and a voltage-controlled capacitor. Calculations predict, and experiments confirm, that an array of SRRs incorporating these nonlinear circuit elements will produce phase conjugation, in which an incoming microwave signal is converted into its time-reversed mirror image. Such effects can be used to correct wave fronts that propagate through distorting media. The authors propose that such active nonlinear metamaterials will find use in rf imaging much like superlensing with negative refractive index materials. – David Voss


Announcements

More Announcements »

Subject Areas

OpticsMetamaterials

Previous Synopsis

Particles and Fields

Uncertain sources

Read More »

Next Synopsis

Cosmology

Cosmic nudity

Read More »

Related Articles

Synopsis: The Helical Factor
Optics

Synopsis: The Helical Factor

An array of helical elements absorbs radiation of a certain frequency while casting no shadow in light over a range of other frequencies. Read More »

Focus: Nanoscale Device Amplifies Fiber-Optic Signals
Optics

Focus: Nanoscale Device Amplifies Fiber-Optic Signals

Researchers have demonstrated an amplifier for near-infrared light that is 20 times more powerful than previous devices and small enough to fit on an integrated circuit. Read More »

Focus: Metamirror Generates Interference at a Distance
Atomic and Molecular Physics

Focus: Metamirror Generates Interference at a Distance

A proposed metasurface made of tiny gold antennas could act as either a flat mirror or a concave, focusing mirror, depending on the radiation pattern of the source, which could lead to new ways to control quantum systems. Read More »

More Articles