Propagation and asymmetric behavior of optical pulses through time-dynamic loss-gain assisted media

TL;DR

This paper investigates how optical pulses behave asymmetrically when passing through a time-varying medium with gain and loss, revealing opposite shifts and spectral changes in different directions, with implications for pulse shaping and novel devices.

Contribution

It introduces a comprehensive analysis of asymmetric pulse propagation in time-dependent media with gain and loss, supported by numerical and analytical results.

Findings

Pulses experience opposite temporal shifts in different propagation directions.

Spectral shifts are opposite for bi-directional pulse propagation.

Peak power and chirp of pulses are opposite regardless of initial conditions.

Abstract

We report an asymmetric behavior of optical pulses during their propagation through a time-varying linear optical medium. The refractive index of the medium is considered to be varying with time and complex such that a sufficient amount of gain and loss is present to realize their effect on pulse propagation. We have exploited the universal formula for optical fields in time-varying media. Numerically simulated results reveal that pulses undergo opposite temporal shifts around their initial center position during their bi-directional propagation through the medium along with corresponding spectral shifts. Moreover, the peak power and accumulated chirp (time derivative of accumulated phase) of the output pulse in both propagation directions are also opposite in nature irrespective of their initial state. Numerically simulated behavior of the pulses agrees well with the analytical solutions. Possibilities have been explored in context of pulse shaping and unconventional optical devices.