ABSTRACT
Millimeter-wave (mm-wave) communications and radar receivers must be protected from high-power signals, which can damage their sensitive components. Many of these systems arguably can be protected by using photonic limiting techniques, in addition to electronic limiting circuits in receiver front-ends. Here we demonstrate, experimentally and numerically, a free-space, reflective mm-wave limiter based on a multilayer structure involving a nanolayer of vanadium dioxide VO2, which experiences a heat-related insulator-to-metal phase transition. The multilayer acts as a variable reflector, controlled by the incident wave intensity. At low intensities VO2 remains dielectric, and the multilayer exhibits strong resonant transmittance. When the incident intensity exceeds a threshold level, the emerging metallic phase renders the multilayer highly reflective while safely dissipating a small portion of the input power, without damage to the limiter. In the case of a Gaussian beam, the limiter has a nearly constant output above the limiting threshold input.
ABSTRACT
We employ random matrix theory in order to investigate coherent perfect absorption (CPA) in lossy systems with complex internal dynamics. The loss strength γ_{CPA} and energy E_{CPA}, for which a CPA occurs, are expressed in terms of the eigenmodes of the isolated cavity-thus carrying over the information about the chaotic nature of the target-and their coupling to a finite number of scattering channels. Our results are tested against numerical calculations using complex networks of resonators and chaotic graphs as CPA cavities.
ABSTRACT
We demonstrate that a three-terminal harmonic symmetric chain in the presence of a Coriolis force, produced by a rotating platform that is used to place the chain, can produce thermal rectification. The direction of heat flow is reconfigurable and controlled by the angular velocity Ω of the rotating platform. A simple three-terminal triangular lattice is used to demonstrate the proposed principle.
