Lineshape distortion in a nonlinear auto-oscillator near generation threshold: Application to spin-torque nano-oscillators

TL;DR

This paper analyzes how thermal noise causes lineshape distortions in nonlinear auto-oscillators near their generation threshold, with a focus on spin-torque nano-oscillators, revealing that distortions signal the threshold.

Contribution

It develops a theoretical model describing lineshape distortions in nonlinear auto-oscillators near threshold, validated by experiments on spin-torque nano-oscillators.

Findings

Lineshape becomes non-Lorentzian near threshold

Distortions serve as signatures of the generation threshold

Theory matches observed behavior of spin-torque nano-oscillators

Abstract

The lineshape in an auto-oscillator with a large nonlinear frequency shift in the presence of thermal noise is calculated. Near the generation threshold, this lineshape becomes strongly non-Lorentzian, broadened, and asymmetric. A Lorentzian lineshape is recovered far below and far above threshold, which suggests that lineshape distortions provide a signature of the generation threshold. The theory developed adequately describes the observed behavior of a strongly nonlinear spin-torque nano-oscillator.