On the effect of self-steepening in modulation instability

TL;DR

This paper analyzes how self-steepening influences modulation instability in optical fibers, revealing a pump power level that maximizes gain and showing that excessive power suppresses MI, with implications for supercontinuum generation.

Contribution

It provides analytical expressions for MI gain including self-steepening effects and uncovers a non-monotonic relationship between pump power and MI gain.

Findings

Existence of an optimal pump power for maximum MI gain

High pump power can suppress modulation instability

Numerical simulations confirm analytical predictions

Abstract

We revisit the problem of modulation instability (MI) in optical fibers, including higher-order dispersion terms, self-steepening, and Raman response. We derive expressions for the MI gain and use them to explore the role of self-steepening towards a high-power limit. We show that, contrary to common wisdom, there is a pump power level that maximizes the MI gain. Further increasing the power not only diminishes the gain, but eventually makes it disappear. We believe these findings to be of special relevance, for instance, when applied to the generation of supercontinuum in the mid and far infrared bands. Finally, numerical simulations confirming our analytical results are presented.