title: PT-symmetry breaking and laser-absorber modes in optical scattering systems.
abstract: Using a scattering matrix formalism, we derive the general scattering properties of optical structures that are symmetric under a combination of parity and time reversal (PT). We demonstrate the existence of a transition between PT-symmetric scattering eigenstates, which are norm preserving, and symmetry-broken pairs of eigenstates exhibiting net amplification and loss. The system proposed by Longhi [Phys. Rev. A 82, 031801 (2010).], which can act simultaneously as a laser and coherent perfect absorber, occurs at discrete points in the broken-symmetry phase, when a pole and zero of the S matrix coincide.
authors.affiliation: Department of Applied Physics, Yale University, New Haven, Connecticut 06520, USA.
authors.forename: Y D
authors.initials: YD
authors.lastname: Chong
authors.forename: Li
authors.initials: L
authors.lastname: Ge
authors.forename: A Douglas
authors.initials: AD
authors.lastname: Stone