Fractional Echoes

TL;DR

This paper reports the first experimental observation of fractional echoes in a nonlinear system, where echoes appear at rational fractions of the pulse delay, demonstrated through third harmonic generation in CO2 molecules.

Contribution

It introduces the concept of fractional echoes, explaining their mechanism and providing the first experimental demonstration in a thermal gas of CO2 molecules.

Findings

Fractional echoes occur at rational fractions of the pulse delay.

Experimental demonstration using third harmonic generation in CO2.

Mechanistic explanation of fractional echo formation.

Abstract

We report the observation of fractional echoes in a double-pulse excited nonlinear system. Unlike standard echoes which appear periodically at delays which are integer multiple of the delay between the two exciting pulses, the fractional echoes appear at rational fractions of this delay. We discuss the mechanism leading to this phenomenon, and provide the first experimental demonstration of fractional echoes by measuring third harmonic generation in a thermal gas of CO2 molecules excited by a pair of femtosecond laser pulses.