A new microwave radiation sensor with 100,000 times higher sensitivity than currently available commercial sensors could revolutionize thermal imaging and electronic warfare.

Researchers said better detection of microwave radiation will enable improved radio communications and radar technology.

This research has found a new pathway to improve the performance of systems detecting electromagnetic signals such as radar, night vision, LIDAR (Light Detection and Ranging), and communication. It could also enable new applications such as quantum information science, thermal imaging as well as the search of dark matter.

Researchers published their study in the peer-reviewed journal Nature. 

“The microwave bolometer developed under this project is so sensitive that it is capable of detecting a single microwave photon, which is the smallest amount of energy in nature,” said Dr. Joe Qiu, program manager for solid-state electronics and electromagnetics, Army Research Office, an element of the US Army Combat Capabilities Development Command’s Army Research Laboratory. “This technology will potentially enable new capabilities for applications such as quantum sensing and radar, and ensure the US Army maintains spectral dominance in the foreseeable future.”

The graphene bolometer sensor detects electromagnetic radiation by measuring the temperature rise as the photons are absorbed into the sensor. Graphene is a two dimensional, one-atom layer thick material. The researchers achieved a high bolometer sensitivity by incorporating graphene in the microwave antenna.

A key innovation in this advancement is to measure the temperature rise by superconducting Josephson junction while maintaining a high microwave radiation coupling into the graphene through an antenna, researchers said. The coupling efficiency is essential in a high sensitivity detection because “every precious photon counts.”

A Josephson junction is a quantum mechanical device which is made of two superconducting electrodes separated by a barrier (thin insulating tunnel barrier, normal metal, semiconductor, ferromagnet, etc.)

In addition to being thin, the electrons in graphene are also in a very special band structure in which the valence and conduction bands meet at only one point, known as Dirac point.

“The density of states vanishes there so that when the electrons receive the photon energy, the temperature rise is high while the heat leakage is small,” said Dr. Kin Chung Fong, Raytheon BBN Technologies.

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