Electrical control of circular polarization in birefringent spin vertical cavity surface emitting laser

Spin vertical cavity surface emitting lasers (spin-VCSELs) reveal unprecedented advantages of spintronics for applications beyond magnetoresistance and have the potential to form a new generation of optical communication systems [1,2]. Till now, the circular polarization is controlled by switching the magnetization thanks to an external magnetic field. For future applications, it is essential to get rid of any external magnetic field. A possible solution could be to switch electrically the magnetization via the spin-orbit torque (SOT) effect [3]. However, the control of the circular polarization by modulating electrically the spin-injection direction remains still a challenging issue. The objective of this PhD thesis is to investigate the electrical control of spin injection in a birefringent spin-VCSEL by employing novel spin injectors that exhibit spin–orbit torque (SOT) effects. The project will involve close collaboration with the research group of Nils Gerhardt at Paderborn University (Germany), which has recognized expertise in spin-laser characterization. During the three-year PhD program, the candidate will spend one year within Prof. Gerhardt’s group, focusing on advanced spin-laser characterization techniques. Beyond demonstrating electrical control of spin injection in spin-VCSELs, this project aims to deepen the understanding of the underlying physical mechanisms, including spin–orbit torque, spin injection, and spin dynamics in spin lasers. References: [1] M. Lindemann, G. Xu, T. Pusch, R. Michalzik, M. R. Hofmann, I. Žutić & N. C. Gerhardt, “Ultrafast spin-lasers”, Nature 568, 212–215 (2019). [2] I. Žutić, G. Xu, M. Lindemann, P. E. Faria Junior, J. Lee, V. Labinac, K. Stojšić, G. M. Sipahi, M. R. Hofmann, N. C. Gerhardt, “Spin-lasers: spintronics beyond magnetoresistance”, Solid State Communications 316–317, 113949 (2020). [3] P. A. Dainone, N. F. Prestes, P. Renucci, A. Bouché, M. Morassi, X. Devaux, M. Lindemann, J.-M. George, H. Jaffrès, A. Lemaitre, B. Xu, M. Stoffel, T. Chen, L. Lombez, D. Lagarde, G. Cong, T. Ma, P. Pigeat, M. Vergnat, H. Rinnert, X. Marie, X. Han, S. Mangin, J.-C. Rojas-Sanchez, J.-P. Wang, M. C. Beard, N. C. Gerhardt, I. Žutić & Y. Lu, “Controlling the helicity of light by electrical magnetization switching”, Nature 627, 783-788 (2024).