USC Researchers Develop First-in-Class Polarization and Color Sensitive Infrared Detectors

By Peijean Tsai, USC Stevens Center for Innovation
Published: August 11, 2020

Two investigators at the USC Viterbi School of Engineering are leading research efforts to develop a new cutting-edge infrared detector technology that could enable a wide range of critical applications—everything from 3D night vision systems, to autonomous vehicles and space exploration, to hyperspectral imaging and biomolecule sensing.

Ravichandran and WangProfessors Jayakanth Ravichandran and Han Wang, who have backgrounds in material sciences and electrical engineering, recently earned a $50,000 USC Stevens Technology Advancement Grant (TAG) to further the development of their project. They are developing novel polarization and color sensitive infrared detectors, which use emerging small band gap semiconductors – black phosphorus and quasi-1D hexagonal chalcogenides – harnessing their unique anisotropic optical properties (where a material changes or assumes different properties in different directions). Their work will develop an array of dynamically tunable infrared photodetectors to achieve polarization and color sensitivity, important aspects they say are still sorely missing in existing infrared detectors available in the commercial market.

The initial research behind the technology was supported by federal grants, which focused on basic scientific research. The TAG award, however, will provide resources to address the commercialization aspect of the materials, according to the researchers.

“We are very excited,” said Wang. “It’s a really great opportunity for us to work with Stevens [Center] and push the technology we have developed from an academic lab to potential commercial applications.”

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The two investigators have collaborated closely for years, leading lab research teams with postdoctoral fellows and graduate student researchers. The origins of the project started over five years ago, when Ravichandran’s and Wang’s labs started researching the fundamental science and basic physical properties of two nano materials: black phosphorus and Barium Titanium Sulfide (BaTiS3), a compound material made of three elements. The breakthroughs in these materials came when Wang and their co-workers discovered exciting anisotropy in the infrared optical properties of Black Phosphorus, a result published in Nature Communications in 2014. Later, Ravichandran, Wang and co-workers discovered even greater record breaking infrared anisotropy in BaTiS3 in 2018, which was published in Nature Photonics. That led to Ravichandran and Wang diving deeper into infrared light — electromagnetic radiation with wavelengths longer than those of visible light that are invisible to the human eye — and how it could be leveraged for developing technology that uses longer infrared wavelengths for several real-world applications in life sciences and engineering. From there, they progressed to synthesizing their own materials, and eventually building a small device that could capture infrared light information that would function as an imaging unit.

Here’s an example of how the USC infrared-based technology could work. Currently, self-driving cars use sensors to detect how far they are from other cars; the technology is based on “near-infrared” light, which has shorter wavelengths than mid-infrared. The USC technology leverages mid-infrared, which has longer wavelengths that are not as easily absorbed into the air as light at shorter wavelengths are. At the longer wavelengths, cars can potentially sense other cars across longer distances and even through foggy or bad weather conditions, said Wang. For these reasons, there is significant interest in the autonomous vehicle industry in technologies based on longer wavelengths like mid-infrared, he said. Additionally, the polarization capabilities of the USC-developed detectors would make systems more sensitive to the edges of objects: “Such detectors can allow the better identification of object edges,” Wang said. “The large-scale deployment of autonomous vehicles will need cost-effective infrared cameras. Currently, there is no known technology that can do that effectively and our approach is expected to solve all the major issues,” Ravichandran said.

There are several other potential applications for the USC-developed technology. It could be useful for night vision, surveillance, and targeting, as “at night, there is rich infrared light present,” Wang said. It could also be used in space, such as helping to capture 3D images and advanced topographical information about the surface of planetary objects. “It could also do body temperature imaging at remote distances, so there can be medical applications as well,” Wang said.

“Our joint work has been extremely fruitful and satisfying,” Ravichandran said. “This [Stevens TAG] award will be critical to take this technology to the next level in terms of commercialization. We hope to work closely with the Stevens Center to make this happen.”

“With a broad breadth of expertise in electronic and photonic technologies, we hope to make a strong impact in this area together at USC. We will be back to Stevens again for our next breakthrough technology very soon,” Ravichandran stated regarding his and Wang’s collaborative research efforts.

PHOTO: Jayakanth Ravichandran (left) and Han Wang are researchers at the USC Viterbi School of Engineering. Ravichandran is an Assistant Professor of Chemical Engineering and Materials Science and Electrical and Computer Engineering. Wang is the Robert G. and Mary G. Lane Endowed Early Career Chair and Associate Professor of Electrical and Computer Engineering and Chemical Engineering and Materials Science.

This article is one in a series of stories written to showcase the USC researchers and their technologies awarded a USC Stevens Technology Advancement Grant (TAG).

The TAG program, which was launched by the USC Stevens Center for Innovation in 2016, supports early-stage technologies invented at USC through validation or proof-of-concept development. TAG awards help to add value to unlicensed USC-owned technology, thereby increasing the probability of licensing and supporting the commercialization of discoveries created at USC. This June, the Stevens Center awarded a total of $150,000 to fund three projects ($50,000 each) across a diverse range of fields at three USC schools: Keck School of Medicine, School of Pharmacy, and Viterbi School of Engineering. The awards are determined annually based on a competitive application process.