Sensor converts radio waves to laser pulses with minimal noise

Nature : Radio wave receivers use resonance in an antenna to induce an electrical signal that is then amplified electronically. However, even when the equipment is supercooled, the amplification process introduces noise into the signal. A new sensor, developed by Eugene Polzik of the University of Copenhagen and his colleagues, converts the radio signal into an optical signal with no electrical amplification. In the sensor, a laser is reflected off a silver nitride membrane, which is coated with a thin layer of aluminum and suspended over a gold plate. As with previous receivers, the radio signal produces an oscillating electrical signal, but instead of being amplified it creates a voltage between the gold plate and aluminum-sided membrane, which causes the membrane itself to oscillate. The oscillation causes pulses in the reflected laser light, which provides an easy-to-read signal that matches the original radio wave, with 100 times less noise than the best previous receivers. The technique could be used in satellite radio telescopes, MRI scans, and quantum technologies; however, the system is still very inefficient.