A researcher has introduced a groundbreaking method for detecting long wave infrared (LWIR) photons across varying wavelengths, or “colors.” This innovative detection and imaging technique will prove valuable for material analysis based on their spectral characteristics, known as spectroscopic imaging, in addition to applications in thermal imaging.
Debashis Chanda, a professor at the University of Central Florida’s (UCF) NanoScience Technology Center, has pioneered a technique that identifies long wave infrared (LWIR) photons of various wavelengths or “colors.”
This research was recently featured in Nano Letters, a journal from the American Chemical Society.
The new technique will be useful for analyzing materials through their spectral properties, also known as spectroscopic imaging, and is expected to enhance thermal imaging applications.
While humans can see primary and secondary colors, we are unable to detect infrared light. However, scientists believe that certain animals, like snakes and some nocturnal creatures, have the ability to recognize different wavelengths in the infrared spectrum similar to human color perception.
Detecting LWIR at room temperature has been challenging because of the low energy of the photons involved, according to Chanda.
LWIR detectors are generally categorized as either cooled or uncooled, the researcher notes.
Cooled detectors are known for their high sensitivity and swift response rates, but their dependence on cryogenic cooling greatly increases their cost and limits practical usage.
On the other hand, uncooled detectors, such as microbolometers, can operate at room temperature and are more affordable, but they typically offer lower sensitivity and slower response times, according to Chanda.
Neither type of LWIR detector currently possesses dynamic spectral tunability, meaning they cannot differentiate the wavelengths of various “colors.”
To overcome the limitations of existing LWIR detectors, Chanda and his team of postdoctoral researchers worked to create a highly sensitive and efficient method utilizing a nanopatterned graphene.
Tianyi Guo, who completed his PhD at UCF in 2023 under Chanda’s guidance, is the lead author of this research. He has received an international thesis award from Springer Nature, and his thesis on potential LWIR detection techniques was published in the Springer Theses book series.
This newly developed method represents the culmination of work by Guo, Chanda, and other members of Chanda’s lab, according to Chanda.
“No existing cooled or uncooled detectors provide the level of dynamic spectral tunability and rapid response that we have demonstrated,” Chanda states. “This finding highlights the promise of engineered monolayer graphene LWIR detectors that work at room temperature, offering high sensitivity and dynamic spectral tunability for advanced spectroscopic imaging.”
The detector’s function is based on a temperature difference in materials—a phenomenon known as the Seebeck effect—within a specially patterned graphene film. When exposed to light, the patterned section generates hot carriers with significantly increased absorption, while the unpatterned area remains at a lower temperature. The movement of these hot carriers results in a photo-thermoelectric voltage, which is then measured between the source and drain electrodes.
By designing the graphene into a unique array, the researchers enhanced absorption and allowed for electrostatic tuning within the LWIR spectrum, leading to improved infrared detection. This new detector greatly outperforms traditional uncooled infrared detectors, such as microbolometers.
“Our proposed detection platform sets the stage for a new generation of uncooled graphene-based LWIR photodetectors, applicable in various fields, including consumer electronics, molecular sensing, and space exploration,” says Chanda.
The research team also includes postdoctoral scholars Aritra Biswas, Sayan Chandra, Arindam Dasgupta, and Muhammad Waqas Shabbir.
The project’s outcomes are backed by a $1.5 million grant from the Extreme Photon Imaging Capabilities program, provided by the Defense Advanced Research Projects Agency, awarded nearly two years ago.
