Monday, September 17, 2012

Faster Photodetector


Researchers have developed a new type of hot electron bolometer that acts as sensitive detector of infra red light. It can be used in application ranging from detection of chemical and bio-chemical weapons from a distance to chemical analysis in the laboratory and studying the structure of the universe through improved telescopes. 
Fast photodetector
They have developed the bolometer using bilayer graphene - two atom-thick sheets of carbon. The bolometer is likely to be sensitive to a very broad range of light energies, ranging from terahertz frequencies or submillimeter waves through infra red to visible light.

Graphene, a single-atom-thick plane of graphite, has some unique properties. Due to band gap of exactly zero energy, it can absorb photons of any energy. This means graphene can even absorb very low energy photons which can pass through most of the semiconductors. Interestingly, it has another, attractive property as photon absorber..The electrons which absorbs the energy are able to retain it efficiently, rather than losing it to the vibrations of the atoms of the material. This property leads to extremely low resistance in graphene.

Researchers exploited these two unique properties of graphene to devise the hot-electrons bolometer. The bolometer works by measuring the change in the resistance that results from the heating of the electron as they absorb light.

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