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Sensor with 100,000x higher sensitivity could bolster thermal imaging, radar

U.S. Army-funded research has developed a new microwave radiation sensor with 100,000 times higher sensitivity than currently available commercial sensors. Its developers said better detection of microwave radiation will enable improved thermal imaging, electronic warfare, radio communications, and radar.

The researchers have published their study in the peer-reviewed journal Nature. The team includes scientists from Harvard University, The Institute of Photonic Sciences, Massachusetts Institute of Technology, Pohang University of Science and Technology, and Raytheon BBN Technologies. The Army, in part, funded the work to fabricate this bolometer by exploiting the giant thermal response of graphene to microwave radiation.

Army-funded research has developed a graphene bolometer sensor with 100,000x higher sensitivity than currently available commercial sensors. Detecting microwave radiation is key to thermal imaging, electronic warfare, radio communications, and radar, but detection sensitivity limits the performance of these systems. [Image courtesy: U.S. Army researchers]

 

 

 

 

"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 U.S. 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 U.S. 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 bolometer detects electromagnetic radiation by measuring the temperature rise as the photons are absorbed into the sensor. The research team fabricated this bolometer by exploiting the giant thermal response of graphene to microwave radiation. [Image courtesy: U.S. Army researchers]

 

 

 

 

A Josephson junction is a quantum mechanical device that 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 a 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.

With increased sensitivity of bolometer detectors, 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 communications. It could also enable new applications such as quantum information science and thermal imaging -- and even aid in the search for dark matter.

The part of the research conducted at MIT included work from the Institute for Soldier Nanotechnologies. The U.S. Army established the institute in 2002 as an interdisciplinary research center to dramatically improve protection, survivability, and mission capabilities of the Soldier and of Soldier-supporting platforms and systems.

Source: U.S. Army CCDC Army Research Laboratory

Published October 2020

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