Nanopatterned graphene enables infrared ‘color’ detection and imaging

Debashis Chanda, a University of Central Florida (UCF) researcher and professor at the UCF Center for Nanoscience and Technology, has developed a new technique to detect longwave infrared (LWIR) photons of different wavelengths, or “colors.”

This research was recently published in Nano Letters.

New detection and imaging techniques will have applications not only in thermal imaging applications, but also in the analysis of materials by spectral properties and spectroscopic imaging.

Humans see primary and secondary colors, but not infrared light. Scientists hypothesize that snakes and other nocturnal animals can detect different wavelengths of infrared light in much the same way humans perceive color.

Detecting infrared light, especially LWIR, at room temperature has been a long-standing challenge because of the low energy of the photons, Chanda said.

According to researchers, LWIR detectors can be broadly divided into cooled and uncooled detectors.

Although cooled detectors offer high detection power and fast response times, their dependence on cryogenic cooling significantly increases cost and limits their practical applications.

In contrast, uncooled detectors like microbolometers work at room temperature and are relatively low cost, but have lower sensitivity and slower response times, Chanda says.

Both types of LWIR detectors do not have dynamic spectral tuning, so they cannot distinguish between the wavelengths of photons of different “colors.”

Aiming to extend beyond the limitations of existing LWIR detectors, Chanda and a team of postdoctoral researchers work to demonstrate a sensitive, efficient, and dynamically tunable method based on nanopatterned graphene. I did.

Tianyi Guo is the study’s lead author. Mr. Guo completed his PhD at UCF in 2023 under Mr. Chanda’s guidance. The newly discovered method is the culmination of research conducted by Guo, Chanda, and others in Chanda’s lab, Chanda says.

“No current detector, cooled or uncooled, offers this kind of dynamic spectral tuning capability and ultra-fast response,” says Chanda. “This demonstration highlights the potential of engineered single-layer graphene LWIR detectors that operate at room temperature and provide high sensitivity and dynamic spectral tuning capabilities for spectroscopic imaging.”

The detector relies on material temperature differences (known as the Seebeck effect) within an asymmetrically patterned graphene film. Upon light irradiation and interaction, the patterned half generates hot carriers with significantly enhanced absorption, while the unpatterned half remains cold. A photothermal voltage is generated by the diffusion of hot carriers and is measured between the source and drain electrodes.

By patterning graphene into special arrangements, researchers can now enhance its absorption and further electrostatically tune it within the LWIR spectral range to provide better infrared detection. This detector significantly exceeds the capabilities of traditional uncooled infrared detectors, also known as microbolometers.

“The proposed detection platform paves the way for a new generation of uncooled graphene-based LWIR photodetectors for a wide range of applications such as consumer electronics, molecular sensing, and space, to name a few.” says Chanda.