A team of physicists from the University of Sheffield has made a step towards the development of optical devices and circuits that enable control and manipulation of photons on a chip via photon spin.
The team were able to realise an effective magnetic field acting on photons in photonic graphene which enabled them to observe the optical version of the spin Hall effect, where photons with opposite circular polarisation propagate in opposite directions.
The motion of electrons in semiconductors is coupled with their spin, which is referred to as spin-orbit interaction. This phenomenon arises from the interaction between the electron spin and the effective magnetic field experienced by a moving electron due to the potential of the crystal lattice.
It leads to the famous spin Hall effect, where flowing electrons with opposite spin are deflected towards opposite directions creating spin currents. Such effects may be harnessed in spintronic applications, which utilise the electron spin for information processing.
On the other hand, photons, which are quanta of electromagnetic radiation, are now also widely used for fast and energy efficient information transfer and processing. The study aimed to realise a compact microscopic system where photons could be made to experience an internal effective magnetic field acting on their polarisation.
This research, which is experimental, builds on recent theoretical studies of photonic graphene where these phenomena were predicted.
The findings, published in Nature Photonics, are a step forward in taking the behaviour of electrons in certain systems and transferring it to photons in carefully designed structures, where these features may be used for a new generation of optical devices and circuits.
Professor Dmitry Krizhanovskii, lead author of the research from the University of Sheffield, said: “Optical signals are now widely used for fast information processing and transfer. For example, optical communication via optical fibers enables high-speed internet connections. Many companies are now working towards the realisation of optical quantum computers, which utilise single photons as quantum bits, and would allow us to solve tasks not possible with current classical computers.
“Our findings pave the way towards the development of novel photonic and optoelectronic spin-based devices for information processing on a microscale.”
