A microwave radiation sensor with 100,000 times higher sensitivity than currently available commercial sensors has recently been developed. The Army partially funded the work to fabricate this bolometer – a sensitive electrical instrument for measuring radiant energy – as better detection of microwave radiation is expected to improve thermal imaging, electronic warfare, LIDAR (Light Detection and Ranging), radio communications, and radar.
“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. “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 bolometer detects electromagnetic radiation by measuring the temperature rise as the photons are absorbed into the sensor. The researchers were able to achieve the high coupling efficiency required for such sensitivity by the use of a Josephson junction – a quantum mechanical device which is made of two superconducting electrodes separated by a barrier. They took a sheet of graphene and placed it in between two layers of superconducting material to create the Josephson junction, attached a microwave resonator to generate the microwave photons, and – by passing these photons through the device – were able to reach unprecedented detection levels. They were able to detect single photons with a much lower energy resolution and achieve detection readouts 100.000 times faster than the fastest nanowire bolometers constructed so far.
The team includes researchers from Harvard University, The Institute of Photonic Sciences, Massachusetts Institute of Technology, Pohang University of Science and Technology, and Raytheon BBN Technologies. The paper was published in the journal, Nature.