Radio wave detector converts signal to light

MIT Technology Review : The ability to detect increasingly faint radio signals is important in a wide range of cutting-edge technologies, including radio astronomy, navigation, and medical imaging. At the smallest spatial scales, filtering out noise often requires cooling detectors with liquid helium. Tolga Bagci of the University of Copenhagen, Denmark, and his colleagues have developed a proof-of-concept nanoscale radio wave receiver that minimizes noise without cooling and converts the radio signal to light. They created a capacitor from a silicon nitride membrane coated with a layer of reflective aluminum and suspended above an electrode. Then they inserted the capacitor into a circuit that resonates at specific radio wave frequencies. When the circuit detected radio waves, it caused the membrane to vibrate. A laser reflecting off the aluminum layer recorded the vibrations as optical phase shifts. The result was a receiver with a room-temperature sensitivity better than any receiver that used ultralow temperatures.