Nano-scale Laser Amplifier Could Lead to Ultra-sensitive Radio Wave Detection

A recent Nature Podcast ( Radio Signals ) features a new type of optical amplifier which converts faint radio signals directly into laser light . The novel approach shows promise with greatly reduced noise and improved sensitivity.

Radio waves are used for many measurements and applications, for example, in communication with mobile phones, MRI scans, scientific experiments and cosmic observations. But 'noise' in the detector of the measuring instrument limits how sensitive and precise the measurements can be. Now researchers at the Niels Bohr Institute have developed a new method where they can avoid noise by means of laser light and can therefore achieve extreme precision of measurements.

We have developed a detector that does not need to be cooled down, but which can operate at room temperature and yet hardly has any thermal noise. The only noise that fundamentally remains is so-called quantum noise, which is the minimal fluctuations of the laser light itself. ... This membrane is an extremely good oscillator and that is why it is so ultrasensitive. At room temperature, it works as effectively as if it was cooled down to minus 271 C and we are working to get it even closer to minus 273 degrees C, which is the absolute minimum. In addition, it is a huge advantage to use optical detection, as instead of using ordinary copper wires to transmit the signal, you can use fiber optic cables, where there is no energy loss, explains Eugene Polzik, Professor and Head of the research center Quantop at the Niels Bohr Institute at the University of Copenhagen.