Spin lasers as coupled harmonic oscillators

A large birefringence in semiconductor spin lasers offers an ultrafast operation in which the polarization of the emitted light can be modulated an order of magnitude faster than the intensity of the emitted light in the best conventional lasers [1,2]. We reveal that the complex dynamical operation in a spin laser can be accurately described by the model of coupled harmonic oscillators. Our description relies on the recently developed nonlinear equations for the intensity of the polarization-resolved emitted light [3]. By linearizing these equations and using a small signal analysis we find that the modulation of the intensity or polarization of the emitted light can be effectively represented by the two weakly-coupled harmonic oscillators of different resonant frequencies. We discuss how this intuitive description of spin lasers allows us to study their unexplored operation regimes and optimize their performance.

[1] M. Lindemann et al., Nature 568, 212 (2019)
[2] I. Zutic et al., Solid State Commun. 316, 11394 (2020)
[3] G. Xu, D. J. Cao, V. Labinac, and I. Zutic, arXiv:2011.01486
.