Comment on 'Counterintuitive Dispersion Violating Kramers-Kronig Relations in Gain Slabs'
arXiv:1407.5549 · doi:10.1103/PhysRevLett.114.089301
Abstract
In this Comment, we refute conclusions made in Phys. Rev. Lett. 112, 233601 (2014) by L.-G. Wang, L. Wang, M. Al-Amri, S.-Y. Zhu, and M. S. Zubairy. These conclusions stem from the use of the linear theory, which is not applicable to systems having poles of the reflection and transmission coefficients in the upper half of the complex frequency plane.