Metamaterials provide active control of 'slow light' devices

Feb 12, 2013
Schematic of active optical control of terahertz waves in electromagnetically induced transparency metamaterials.

LANL researchers and collaborators have made the first demonstration of rapidly switching on and off "slow light" in specially designed metamate­rials at room temperature. Metamaterials are assemblies of multiple individual elements fashioned from conventional microscopic materials arranged in periodic patterns. This work opens the possibility to design novel chip-scale, ultrafast devices for applications in terahertz wireless communications and all-optical computing.

Significance of the research

In slow light, a propagating light pulse is substantially slowed down (compared with the velocity of light in a vacuum). This is accomplished by the interaction with the medium in which the propagation takes place. Slow light has potential applications in telecommunications because it could lead to a more orderly traffic flow in networks. Like cars slowing down or speeding up to negotiate an intersection, packets of information can be better managed if their transmission speed is changeable.

Another potential application is the storage of information carried by , leading to a potential all- system. Current used in computing devices are reaching some of their limits, and an all-optical system would potentially enable improvements in size reduction and calculation speeds. The effects of strong light-matter coupling used in slowing down light might be used to create , leading to quantum computing capabilities beyond the capabilities of modern computers.

Research achievements

Electromagnetically induced transparency is a effect that produces a sharp resonance with extremely low loss and dispersion. However, implementing electromagnetically induced transparency in chip-scale applications is difficult due to the demands of stable gas lasers and low-temperature environments. are engineered containing structures that are smaller than the wavelength of the waves they affect. Metamaterial analogues of electromagnetically induced transparency phenomena enable a unique route to endow classical optical structures with aspects of quantum optical systems.

The researchers integrated photoconductive silicon into the metamaterial unit cell. This material enables a switching of the transparency resonance window through the excitation of ultrafast femtosecond optical pulses. This phenomenon causes an optically tunable group delay of the terahertz light. The "slow light" behavior can be controlled at an ultrafast time scale by integrating appropriate semiconductor materials with conventional metamaterial designs.

In this research, the medium is an active metamaterial that supports a sharp resonance, which leads to a rapid change in the refractive index of the medium over a small range of frequencies. This phenomenon causes a dramatic reduction in the velocity of terahertz light propagation. The resonance can be switched on and off on a time scale of a few pico-seconds (a pico-second is 10-12 second). When the resonance transparency is on, the system produces slow light. When the resonance is off, the slow light behavior disappears. This on and off process happens on an ultrafast (pico-second) time scale when a femto-second (10-15 second) laser pulse excites the metamaterial.

Nature Communications published the research.

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User comments : 4

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not rated yet Feb 12, 2013
So if the incoming light is a coherent light source, they could control the phase difference at each point of the screen, right? Couldn't that be used for real-time holographic displays?
not rated yet Feb 12, 2013
Technically speaking, hologram IS a metamaterial mimicking a structured mirror.
1 / 5 (1) Feb 12, 2013
In slow light, a propagating light pulse is substantially slowed down (compared with the velocity of light in a vacuum). This is accomplished by the interaction with the medium in which the propagation takes place. …

This is interesting, but the problem is that we still do not understand why light wave speed is the fastest speed in vacuum! The physical view may help us to visualize its mechanism…
not rated yet Feb 13, 2013
I found this very intersting. Lene Vestergaard Hau was able to stop light at one point. In 2005 IBM was the first to make a microchip that slowed light. I also saw that in this article: a researcher was also slowing light. This slowed light can potentially create all-optical switches, single-photon detectors, and quantum memory devices. This will really improve the efficiency of computers and their memory.

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