Researchers study the mechanisms for detecting circularly polarized light using spin photodiodes

An international collaboration involving the Irradiated Solids Laboratory at EPFL has published a paper detailing the mechanisms for detecting circularly polarized light using spin-optoelectronic devices called spin photodiodes.

“In this work, we combined spintronics with optics. This is spin-optoelectronics,” explains Henri-Jean Drouhin, co-author of the study published and head of the ‘Physics and Chemistry of Nano-objects’ group at the Irradiated Solids Laboratory (LSI). Light particles, photons, also have a spin. This spin manifests itself in the fact that light can be right- or left-handed circularly polarized (which means that the electric field of the light winds to the right or left like a helix in the direction of propagation of the photons). When this light hits the device designed by the researchers, photons can excite electrons in the material. The spin of these electrons then adopts a preferential direction that depends on the photon spin. Knowing how to selectively extract the electrons therefore makes it possible to obtain information on the polarization of the incident light, making these devices ‘spin photodiodes’, in contrast to conventional photodiodes that measure the intensity of the light.