Resonators fold the path of light by reflections leading to a
phase balance and thus constructive addition of propagating waves.
However, amplitude decrease of these waves due to incomplete reflection
or material absorption leads to a finite quality factor of all resonances.
Here we report on our discovery that evanescent waves can lead to a perfect
phase and amplitude balance causing an ideal Fabry-Perot resonance condition
in spite of material absorption and non-ideal reflectivities.
This counterintuitive resonance occurs if and only if
the metallic Fabry-Perot plates are in relative motion
to each other separated by a critical distance. We show
that the energy needed to approach the resonance arises
from the conversion of the mechanical energy of motion
to electromagnetic energy. The phenomenon is similar to
lasing where the losses in the cavity resonance are exactly
compensated by optical gain media instead of mechanical motion.
Nonlinearities and non-localities in material response will inevitably
curtail any singularities however we show the giant enhancement in
non-equilibrium phenomena due to such resonances in moving media.

We recently reported on the existence
of a singular resonance in moving media
which arises due to perfect amplitude and
phase balance of evanescent waves. We show
here that the nonequilibrium vacuum friction
(lateral Casimirâ€“Lifshitz force) between moving plates separated
by a finite gap is fundamentally dominated by this resonance.
Our result is robust to losses and dispersion as well as polarization
mixing which occurs in the relativistic limit.

Vacuum consists of a bath of balanced and symmetric positive- and negative-frequency fluctuations. Media in relative motion or accelerated observers can break this symmetry and preferentially amplify negative-frequency modes as in quantum Cherenkov radiation and Unruh radiation. Here, we show the existence of a universal negative-frequency-momentum mirror symmetry in the relativistic Lorentzian transformation for electromagnetic waves. We show the connection of our discovered symmetry to parity-time (PT) symmetry in moving media and the resulting spectral singularity in vacuum fluctuation-related effects. We prove that this spectral singularity can occur in the case of two metallic plates in relative motion interacting through positive- and negative-frequency plasmonic fluctuations (negative-frequency resonance). Our work paves the way for understanding the role of PT-symmetric spectral singularities in amplifying fluctuations and motivates the search for PT symmetry in novel photonic systems.

Explore how engineered materials and 2D materials can be exploited for thermal radiation beyond the black-body limit.

We have shown that spin polarized thermal radiation is a striking feature of non-equilibrium as well as non-reciprocal systems.

High temperature materials with unique properties are a major focus of our research with multiple engineering applications.