Synthetic phonons enable nonreciprocal coupling to arbitrary resonator networks

TL;DR

This paper introduces synthetic phonons to enable customizable nonreciprocal coupling in resonator networks, allowing for advanced, reconfigurable nonreciprocal devices across various wave systems.

Contribution

It demonstrates how synthetic phonons can be used to achieve nonreciprocal coupling with customizable frequency responses, surpassing previous broadband or Lorentzian limitations.

Findings

Successfully implemented nonreciprocal coupling in microstrip circuits.

Demonstrated elementary nonreciprocal functions like isolation and gyration.

Created reconfigurable, higher-order nonreciprocal filters.

Abstract

Inducing nonreciprocal wave propagation is a fundamental challenge across a wide range of physical systems in electromagnetics, optics, and acoustics. Recent efforts to create nonreciprocal devices have departed from established magneto-optic methods and instead exploited momentum based techniques such as coherent spatiotemporal modulation of resonators and waveguides. However, to date the nonreciprocal frequency responses that such devices can achieve have been limited, mainly to either broadband or Lorentzian-shaped transfer functions. Here we show that nonreciprocal coupling between waveguides and resonator networks enables the creation of devices with customizable nonreciprocal frequency responses. We create nonreciprocal coupling through the action of synthetic phonons, which emulate propagating phonons and can scatter light between guided and resonant modes that differ in both frequency and momentum. We implement nonreciprocal coupling in microstrip circuits and experimentally demonstrate both elementary nonreciprocal functions such as isolation and gyration as well as reconfigurable, higher-order nonreciprocal filters. Our results suggest nonreciprocal coupling as platform for a broad class of customizable nonreciprocal systems, adaptable to all wave phenomena.