Unidirectional amplification in the frozen mode regime enabled by a nonlinear defect.

A stationary inflection point (SIP) is a spectral singularity of the Bloch dispersion relation ω(k) of a periodic structure where the first and the second derivatives of ω with respect to k vanish. An SIP is associated with a third-order exceptional point degeneracy in the spectrum of the unit-cell transfer matrix, where there is a collapse of one propagating and two evanescent Bloch modes. At the SIP frequency, the incident wave can be efficiently converted into the frozen mode with greatly enhanced amplitude and vanishing group velocity.

Directed emission from uniformly excited non-Hermitian photonic meta-structures.

We investigate the emission characteristics of a tri-atomic photonic meta-molecule with asymmetric intra-modal couplings which is uniformly excited by an incident waveform tuned to coherent virtual absorption conditions. By analyzing the dynamics of the discharged radiation, we identify a parameter domain where its directional re-emission properties are optimal.

Scaling theory of absorption in the frozen mode regime.

A stationary inflection point (SIP) of the Bloch dispersion relation of a periodic system is a prominent example of an exceptional point degeneracy (EPD) where three Bloch eigenmodes coalesce. The scattering problem for a bounded photonic structure supporting a SIP features the frozen mode regime (FMR), where the incident wave is converted into the "frozen mode" with vanishing group velocity and diverging amplitude. We analyze the effect of losses and disorder on the FMR and develop a scaling formalism for the absorbance in the FMR that takes into consideration losses, disorder, and system size.