Nanowire-based bolometer circumvents diffraction limit

Bolometers absorb radiation and heat up, and quantifying the temperature change leads to a measurement of the radiation. Bolometers can work throughout the electromagnetic spectrum, often used in infrared cameras and as detectors for infrared and terahertz radiation.

Papas et al. developed a bolometer based on nanowires, which naturally oscillate at megahertz frequencies.

“When the nanowires are heated by radiation absorption, they expand, causing them to oscillate at a lower frequency,” said author Eric Plum. “The oscillation of the nanowires modulates light, allowing the oscillation frequency to be observed from a distance.”

The process is analogous to tuning a musical instrument. Like a musician adjusts the tension in a musical string to change its pitch, the incoming radiation changes the tension and oscillation frequency of the nanowire. While the string’s vibration is heard as music, the nanowire’s vibration is seen as light modulation.

The nanowire bolometer offers nanoscale spatial resolution, improving previous bolometer arrays by more than an order of magnitude. It also responds to illumination 100 times faster than other arrays.

“The resolution of normal optical techniques is limited by diffraction to about half a wavelength,” said Plum. “We are able to circumvent the diffraction limit by detecting light modulation caused by the oscillation of different nanowires at different frequencies. Therefore, the spatial resolution of our optical nanobolometer is determined by the size of the nanowires, rather than the wavelength of light.”

This bolometer offers an opportunity to make high spatial resolution radiation detectors. The team hopes to develop the technology further to realize ultracompact spectrometers and polarimeters.

Source: “Optomechanical metamaterial nanobolometer,” by Dimitrios Papas, Jun-Yu Ou, Eric Plum, and Nikolay I. Zheludev, APL Photonics (2021). The article can be accessed at https://doi.org/10.1063/5.0073583 .