Reflectionless Programmable Signal Routers

TL;DR

This paper demonstrates reflectionless programmable signal routers using reflectionless scattering modes in microwave cavities, enabling versatile, low-reflection signal routing with potential applications in RF and photonic networks.

Contribution

It introduces a novel method to achieve reflectionless, programmable signal routing using RSMs in microwave cavities with a programmable metasurface, expanding the understanding of multi-resonance transport.

Findings

Achieved reflectionless routing with negligible in-coupling reflection.

Demonstrated wavelength demultiplexing and multi-channel routing.

Showed broadening of damping rates under strong absorption in simulations.

Abstract

We demonstrate experimentally that reflectionless scattering modes (RSMs), a generalized version of coherent perfect absorption, can be functionalized to perform reflectionless programmable signal routing. We achieve versatile programmability both in terms of operating frequencies and routing functionality with negligible reflection upon in-coupling, which avoids unwanted signal-power echoes in radio-frequency or photonic networks. We report in-situ observations of routing functionalities like wavelength demultiplexing, including cases where multi-channel excitation requires adapted coherent input wavefronts. All experiments are performed in the microwave domain based on the same irregularly shaped cavity with strong modal overlap that is massively parametrized by a 304-element programmable metasurface. RSMs in our highly overdamped multi-resonance transport problem are fundamentally intriguing because the simple critical-coupling picture for reflectionless excitation of isolated resonances fails spectacularly. We show in simulation that the distribution of damping rates of scattering singularities broadens under strong absorption so that weakly damped zeros can be tuned toward functionalized RSMs.