Reviewed by Lexie CornerDec 13 2024
Debashis Chanda, a professor at the University of Central Florida’s (UCF) NanoScience Technology Center, has developed a new technique for detecting long-wave infrared (LWIR) photons at distinct wavelengths, or "colors."
This breakthrough is the result of a $1.5 million project funded by the Defense Advanced Research Projects Agency’s (DARPA) Extreme Photon Imaging Capabilities program, which was awarded nearly two years ago.
The new detection and imaging method will be used for spectroscopic imaging—analyzing materials based on their spectral features—as well as for thermal imaging applications.
While humans can see primary and secondary colors, infrared light is beyond our visual range. However, scientists believe that certain animals, like snakes and nocturnal species, can detect different wavelengths in the infrared, much like how we perceive visible colors.
According to Chanda, detecting infrared, especially LWIR, at room temperature has been challenging due to the low energy of these photons.
The study explains that LWIR detectors typically fall into two categories: cooled and uncooled. Cooled detectors offer high sensitivity and quick response times but require cryogenic cooling, making them expensive and limiting their practical use. On the other hand, uncooled detectors, like microbolometers, work at room temperature and are more affordable but are less sensitive and slower to respond.
Both types of detectors lack the ability to tune dynamically across different wavelengths, meaning they can't differentiate between photons of varying "colors."
To address these limitations, Chanda and his team of postdoctoral scholars developed a highly sensitive, efficient, and dynamically tunable technique based on nanopatterned graphene.
The lead author of the study is Tianyi Guo, who completed his Ph.D. at UCF in 2023 under Chanda’s guidance. Guo received an international thesis award from Springer Nature, and his work on LWIR detection methods was published in the prestigious Springer Theses book series.
Guo, Chanda, and other members of Chanda’s team conducted the research that led to this new detection approach.
No present cooled or uncooled detectors offer such dynamic spectral tunability and ultrafast response. This demonstration underscores the potential of engineered monolayer graphene LWIR detectors operating at room temperature, offering high sensitivity as well as dynamic spectral tunability for spectroscopic imaging.
Debashis Chanda, Professor, University of Central Florida
The detector relies on a temperature difference between materials, known as the Seebeck effect, within an asymmetrically patterned graphene layer. When the graphene is illuminated, the patterned section generates hot carriers with much higher absorption, while the unpatterned section remains cool. The movement of these hot carriers creates a photothermoelectric voltage, which is then measured between the source and drain electrodes.
To achieve increased absorption, the researchers patterned the graphene into a specific array. This array can be electrostatically tuned within the LWIR spectrum, allowing for superior infrared detection. As a result, the detector significantly outperforms traditional uncooled infrared detectors, such as microbolometers.
Chanda added, “The proposed detection platform paves the path for a new generation of uncooled graphene-based LWIR photodetectors for wide-ranging applications such as consumer electronics, molecular sensing, and space, to name a few.”
Postdoctoral scholars Aritra Biswas ’21MS ’24Ph.D., Sayan Chandra, Arindam Dasgupta, and Muhammad Waqas Shabbir ’16MS ’21Ph.D. are among the researchers from Chanda’s group.