Nanoscale trampoline-like sensor measures light mechanically
The technology, known as a “graphene nanomechanical bolometer,” offers an alternative to the conventional way of using electricity to measure light – such as found in devices like a smartphone’s camera – by leveraging a mechanical method and new material to detect nearly every color of light at high speeds and high temperatures. The tool, say the researchers, is the fastest and most sensitive in its class.
The new method captures the vibrations of infinitesimally thin drums that occur when they are hit by light. Measurements are obtained by listening to the sound of the light absorbed by the drumhead, an effect similar to that of banging a drum on a hot day – as the instrument heats up under the hot sun the drumhead membrane expands and its pitch changes, emitting a different tone than it would at cooler temperatures.
The same thing occurs with the mechanical bolometers: as the waves of light hits the device’s drumhead, the membrane heats up, expands, and the vibrational pitch changes. The researchers can track these pitch changes to measure how much light hits the device.
“This is a very new way of detecting light,” says David Miller, a doctoral student in the University’s experimental physics lab. “We’re using a purely mechanical method to turn light into sound. This has the advantage of being able to see a much broader range of light.”
While conventional detectors are very reliable at reading high-energy light, like visible light or X-rays, say the researchers, they are less adept at measuring the longer wavelengths on the electromagnetic spectrum, including infrared and radio waves. Their mechanical device fills that void and allows detection of light of nearly any wavelength, which could be especially useful in astronomical observations, thermal and medical body imaging, and seeing deep into the infrared.
The device was constructed by first stretching a thin sheet of graphene – which consists of a single layer of atoms – over a hole etched into a piece of silicon. The sheet was then cut to resemble a miniscule trampoline (image).
The mechanical properties of graphene, say the researchers, allow the material to respond to temperature changes incredibly fast, which enables it to measure light at equally speedy rates.
“Graphene offered a tantalizing prospect for ultrasensitive and ultrafast light detection,” says Andrew Blaikie, another doctoral student in the lab and lead author of a paper on the research. “It also possesses an unmatched ability to measure nearly any wavelength of light and can withstand much higher temperatures than conventional detectors.”
The device’s ability to perform at such a wide range of temperatures, say the researchers, is one of its most advantageous qualities when it comes to measuring light. It can operate at room temperature, which allows for critical portability, and it can perform under high heat, which is a benefit that traditional light detectors don’t offer, they say.
“Graphene,” says Blaikie, “is a thermally stable material that can withstand temperatures over 2,000 degrees Celsius.”
Graphene’s versatility and ultrasensitive nature, say the researchers, position the nanomechanical bolometer to be a useful tool in many arenas across science, medicine, industrial manufacturing, and astronomy.
“We hope this device will help scientists crack the mysteries of our sun and other stars, improve medical diagnostics through safer thermal X-ray imaging, and help firefighters see better in fires to save more lives,” says Benjamín Alemán, a professor of physics and member of the University’s Center for Optical, Molecular, and Quantum Science.
The lab currently has a patent pending for the technology. For more, see “A fast and sensitive room-temperature graphene nanomechanical bolometer.”
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