The University of Tokyo has created a thermo-mechanical micromachine that can sense terahertz electromagnetic radiation, without the need for cryogenic cooling. THz cameras is a possible application.
The device is a beam suspended across a gap, coated with a resistive nickel-chromium (NiCr) film.
The film absorbs THz radiation, that transfers as heat to the beam, whose resonant frequency changes at it then expands.
“Using our doubly clamped microelectromechanical beam made of gallium arsenide, we could effectively sense THz radiation at room temperature,” said researcher Kazuhiko Hirakawa. “This structure is particularly effective as it can detect THz radiation very quickly.”
It is also extremely sensitive, according to the University, detecting radiation that causes changes in temperature as small as one-millionth of a degree.
“Another advantage of this system is that it can be produced using standard methods for fabricating semiconductor devices, which would potentially allow its incorporation into mass-produced THz-based sensors and cameras,” said fellow researcher Ya Zhang.
The work is published in the Journal of Applied Physics as ‘Fast and sensitive bolometric terahertz detection at room temperature through thermomechanical transduction‘ – abstract only available free.
According to the abstract:
Owing to its ultra-high temperature sensitivity [~1μK/√Hz noise equivalent temperature difference], the bolometer achieves not only high sensitivity but also an operation bandwidth of several kHz, which is more than 100 times faster than other uncooled THz thermal sensors. The obtained electrical noise equivalent power is as low as ~90pW/√Hz, which is close to the limit set by the thermal fluctuation noise.
