INjection of Spin for PolarIzed Radiation Emission – INSPIRE

Electrons have a charge and a spin, but until recently, charges and spins have been considered separately. In conventional electronics, the charges are manipulated by electric fields but the spins are ignored. Other classical technologies, magnetic recording, for example, are using the spin but only through its macroscopic manifestation, the magnetization of a ferromagnet. This picture started to change in 1988 when the discovery of the giant magnetoresistance _GMR_ of the magnetic multilayers opened the way to an efficient control of the motion of the electrons by acting on their spin through the orientation of a magnetization. This rapidly triggered the development of a new field of research and technology, today called spintronics and, like the GMR, exploiting the influence of the spin on the mobility of the electrons in ferromagnetic materials. Semiconductor spintronics device physics is progressing along a similar path to metallic spintronics and has achieved remarkable success in the last decade.
What we want to mainly explore is the conversion of an electrical spin polarized current into a circular polarized light and how we can take advantage of this effect to built spin polarized VECSEL. We can already anticipate that the ability to control and/or modulate the output polarization of lasers to electrically switch between orthogonal polarization states would be useful for host applications including i)coherent detection system, ii) new modulation formats for optical communications, optoelectronic oscillators and high precision clocks, iii) entangled states for secure communication and quantum cryptography, iiii) and optical switching. As a necessary requirement to progress, basic research including understanding of the spin relaxation mechanisms, material optimization of efficient spin injector and dynamic of the output signals will take a large part. The experimental answer of how much and how far can we drive a spin polarized current into a semiconductor will be a determining clue of this project.
This project comes from a previous funded PNANO project MOMES ends in April 2009. It has brought together 7 partners and has covered a large area in the field of spintronic with semiconductors. The present proposal is one of the issue point identified as successful and needed to be pursued. 3 of the 4 partners of this project were already involved in the previous program. They already have the know how to built efficient spin injector CoFeB/MgO on top of III-V materials and they have demonstrated high conversion of spin polarized current in polarized circular light (<50%) in Spin LED experiment. The next step but not the less along this proposal is to extend this realisation to spin VECSEL. The active participation of the Thales company in this goal is a supplementary asset which will certainly benefit to speed up technological transfer from fundamental research to applied research.