The propagation of light in a pair of waveguides (WGs) with a complex index of refraction is studied, when the WG parameters are adjusted in such a way as to bring the system extremely close to an exceptional point (EP) while slightly breaking $\mathcal{P}\mathcal{T}$ symmetry. We find that this breaking of $\mathcal{P}\mathcal{T}$ symmetry does not affect the structure of the output signals, although the corresponding propagation constants become slightly complex. Only for sufficiently strong breaking of the $\mathcal{P}\mathcal{T}$ symmetry the signal is enhanced or suppressed in a substantial manner. Moreover, due to the EP it is impossible to tap light into another WG and thus read the transmitted signal without destroying completely the nodal structure and changing dramatically the intensity of the signal.

• Received 17 October 2020
• Accepted 17 February 2021

DOI:https://doi.org/10.1103/PhysRevA.103.033518