Michael Woodley and Leo Del-Bino, postgraduate researchers in Quantum Technologies from NPL and Heriot-Watt University, studied the strange physics that occurs when an incredible amount of light is confined within a very small volume of material – a field known as nonlinear optics. To do this they engineered small glass rings called micro-resonators, which can also be integrated into a silicon chip, that trapped laser light inside them by total internal reflection.

It is very difficult for light to escape from the ring, so as we keep adding light the optical power inside these structures can become the equivalent of a football field lighting system in less than a human hair. It gets even more interesting if two laser beams are sent into the resonator in opposite directions, because the nonlinear interaction can result in a spontaneous symmetry breaking of the powers of the two fields. Essentially, light can propagate in one direction but not in the other, and we can control which direction goes through.

This research is not only fascinating from the perspective of fundamental physics, but it can also be implemented in integrated circuits creating myriad applications for all-optical devices and components. The PGI researchers have been awarded the Milton Chang prize by the committee for the Conference on Lasers and Electro-Optics (CLEO) in 2017, the Rayleigh award by NPL in 2018 and with a grant from the Laboratoire Jean-Alexandre Dieudonné for the Waves Côtes d’Azur conference in 2019.  This research was funded by the EPSRC, as part of the CDT in Applied Photonics, and NPL.