The dynamics of circular polarization in spin-lasers.

Through angular momentum conservation, injecting spin-polarized carriers in semiconductor lasers offers control of the helicity of emitted light [1,2]. This improves the operation of lasers, beyond what is possible with injecting unpolarized cariers [1] and offers paths for room-temperature spintronic applications, beyond magnetoresistance [2]. While dynamical operation of spin-lasers and their ultrafast switching [1] is crucial for possible applications, many operation regimes and effects remain unexplored [2,3]. In particular, the role of modulating carrier injection on the circular polarization of the emitted light in scaled-down spin-lasers is not understood. Even in the steady-state regime an enhanced contribution of spontaneous emission, usually assumed to be negligibly small, can strongly change their operation [4]. For the dynamical operation of spin-lasers we find various nonmontonic trends in materials parameters on the key properties, including the helicity of the emitted light and modulation bandwidth. We provide guidance for an optimized design of scaled-down spin- lasers.

[1] M. Lindemann et al., Nature 568, 212 (2019)

[2] I. Zutic et al., Solid State Commun. 316-317, 113949 (2020)

[3] J. Lee et al., Appl. Phys. Lett. 105, 042411 (2014)

[4] G. Xu et al., Appl. Phys. Lett. 119, 171104 (2021)