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: Position Detector Approaches the Heisenberg Limit
Quantum Physics

Synopsis: Position Detector Approaches the Heisenberg Limit

The light field from a microcavity can be used to measure the displacement of a thin bar with an uncertainty that is close to the Heisenberg limit. Read More »

Viewpoint: Next Generation Clock Networks
Atomic and Molecular Physics

Viewpoint: Next Generation Clock Networks

Free-space laser links have been used to synchronize optical clocks with an unprecedented uncertainty of femtoseconds. Read More »

Focus: How to Make an Intense Gamma-Ray Beam
Optics

Focus: How to Make an Intense Gamma-Ray Beam

Computer simulations show that blasting plastic with strong laser pulses could produce gamma rays with unprecedented intensity, good for fundamental physics experiments and possibly cancer treatments. Read More »

More Articles