A new graphene-based light detector is capable of measuring wavelengths of light much to long for the human eye to see.
Terahertz radiation, sometimes called submillimeter radiation, is located in between infrared and microwave frequencies on the electromagnetic spectrum. Development of transmitters and detectors able to function at these frequencies would produce more sensor equipment with much greater sensitivity than today's technology.
Graphene, a sheet of carbon one atom thick, has remarkable electronic and physical properties. Among these is the ability to absorb a wide range of electromagnetic frequencies, making it ideal for use as a terahertz detector. T-Waves can pass through most materials with ease, and can be used to identify the substances through which they pass.
"University of Maryland researchers have discovered a way to control magnetic properties of graphene that could lead to powerful new applications in magnetic storage and magnetic random access memory," the Center for Nanophysics and Advanced Materials, stated on their Web site.
Light striking graphene in the detector excites atoms of carbon in the material. This excess energy is quickly drained to surrounding molecules. If electrical contacts are placed on the graphene, this energy will head toward the metal. Using two different materials for the contacts, such as chromium and gold, creates a current in the device. Measurement of the electrical flow allows a measurement of the amount of terahertz energy is being absorbed by the detector.
"Light is absorbed by the electrons in graphene, which heat up but don't lose their energy easily. So they remain hot while the carbon atomic lattice remains cold," says Dennis Drew, a research scientist at the University of Maryland, said.
The graphene detector is just as sensitive, and several times faster than similar devices based on current technology.
Uses of the new technology could include advances in food and drug inspection, high-speed communications and security scanning equipment. People attempting to smuggle drugs or explosives through airports could easily be examined using T-waves, without fear of harm or inconvenience to other travelers.
Golay cells are able to reliably detect T-waves, but they can take an entire second to react to a change in radiation. Pyroelectric detectors are significantly faster, but are significantly less sensitive.
Future development will look at ways of improving the efficiency of the new device. This will include experiemts using various materials for use in contacts, as well as "stacking" layers of graphene, in an effort to increase sensitivity beyond those currently available levels.
Development of the graphene detector for T-waves was profiled in the journal Nature Nanotechnology.
