Array oscillator in coupled waveguides with nonlinear gain and radiation resistances saturating at exceptional point

TL;DR

This paper presents a novel waveguide array oscillator that leverages exceptional point degeneracy to achieve stable, low-noise, high-power radiation with uniform gain and power distribution, independent of array length.

Contribution

It introduces a new array oscillator design utilizing EPD for stable, uniform oscillation frequency and gain, validated through experiments showing low phase noise and uniform power.

Findings

Oscillation frequency is independent of array length.

System saturates at an exceptional point with low phase noise.

Experimental results confirm uniform power and gain distribution.

Abstract

A periodically loaded waveguide composed of periodic discrete nonlinear gain and radiating elements supports a stable oscillation regime related to the presence of an exceptional point of degeneracy (EPD). After reaching saturation, the EPD in the system establishes the oscillation frequency. We demonstrate a synchronization regime at a stable oscillation frequency, resulting in uniform saturated gain across the array and uniform radiating power. Unlike conventional one-dimensional cavity resonances, the oscillation frequency is independent of the array length. Our investigations further show that when small-signal gain is non-uniformly distributed across the array, the saturated gain results in having a uniform distribution at a gain value that generates an EPD. Experimental validation using the measured board confirmed that the system saturates at an EPD, with a measured spectrum exhibiting very low phase noise. This low noise allows for operation at a clean oscillation frequency. Additionally, the measured uniform power across the array corresponds to the simulation results. The proposed scheme can pave the way for a new generation of high-power radiating arrays with distributed active elements.