High-birefringence spin lasers as coupled harmonic oscillators

While birefringence-anisotropy of the refractive index-is usually considered detrimental in lasers, recent breakthroughs reveal that a large birefringence is responsible for an ultrafast operation of semiconductor lasers with injected spin-polarized carriers [1]. The modulation of the emitted polarization of light in such spin lasers can be realized much faster than the modulation of the light intensity. A transparent description of high-birefringence lasers is provided by recently developed intensity equations [2], which we show to be directly connected to the coupled damped and driven harmonic oscillators. An intuitive understanding of this mechanical analog allows us recover the main trends for the dynamical operation of spin lasers under both intensity and polarization modulation, including the resulting bandwidths. While the experiments on dynamical operation of spin lasers are currently limited to the regime which corresponds to the case of weakly-coupled harmonic oscillators, we also make predictions for an unexplored regime of spin lasers that are represented by a strong-coupling regime [3]

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

2. G. Xu, J. Cao, V. Labinac, and I. Žutić, PRB 103, 045306, (2021)

3. V. Labinac et al., preprint.