Affiliation:
1. Air Force Research Laboratory
Abstract
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. This can be very attractive
for applications, including light amplification. Due to its
non-resonant nature, the frozen mode regime (FMR) has fundamental
advantages over common cavity resonances. Here, we propose, a novel,
to the best of our knowledge, scheme for FMR-based unidirectional
amplifiers by leveraging a tailored amplification/attenuation
mechanism and a single nonlinear defect. The defect breaks the
directional symmetry of the periodic structure and enables
nonlinearity-related unidirectional amplification/attenuation in the
vicinity of the SIP frequency. We demonstrate the robustness of the
amplification mechanism to local impurities and parasitic
nonlinearity.
Funder
KBR Wyle Services
Air Force Office of Scientific
Research
Office of Science