Propagation of intense few-cycle laser pulse in a telecommunication-type optical fiber: analysis of the error introduced by the unidirectional approximation

TL;DR

This paper investigates the propagation of intense few-cycle laser pulses in optical fibers beyond the unidirectional approximation, analyzing the error introduced and validating an analytical estimate through numerical simulations.

Contribution

It provides a new analytical method to estimate the error of the unidirectional approximation in modeling intense pulse propagation in optical fibers.

Findings

The unidirectional approximation error manifests as weak forward and backward pulses.

The analytical error estimate matches numerical simulation results.

High intensities generate octave-spanning continua in fibers.

Abstract

Propagation of few-cycle laser pulses in optical fiber is investigated beyond the unidirectional approximation. Considered medium parameters include dispersion, Kerr and Raman nonlinearities. High intensities of ~10^10 kW/cm^2 lead to generation of the octave-spanning continuum. The error of the unidirectional approximation is seen in simulations as two pulses propagating forwards and backwards, both remain weak under the considered conditions. Direct analytical estimate of the error is derived and verified numerically. It can be applied to a priory justification of the unidirectional approach.