Optical Pulses in a Non-Hermitian Medium near a Singularity

The spectral method was used to solve the problem of interaction of short optical pulses with PT‑symmetric photonic crystals under conditions of frequency singularity. It was shown that, at a small deviation from the exceptional point of spontaneous decay of PT-symmetric field modes, frequency singularities of the transmission and reflection coefficients of the structure arise. This leads to a significant narrowing of the pulse spectra and an increase in their amplitude and duration with unidirectional Bragg reflection.