Compression and collisions of chirped pulses in a dense two-level medium

TL;DR

This study uses numerical simulations to analyze how linearly-chirped optical pulses propagate, compress, and collide in a dense two-level medium, revealing limitations of the RWA and potential for controlled pulse interactions.

Contribution

It demonstrates the inaccuracy of the RWA for chirped pulse interactions and explores pulse compression and collision effects for long and single-cycle pulses.

Findings

RWA does not accurately describe chirped pulse interactions.

Chirp influences pulse compression differently for long and single-cycle pulses.

Collisions can be used to control transmitted radiation and medium excitation.

Abstract

Using numerical simulations, we study propagation of linearly-chirped optical pulses in a homogeneously broadened two-level medium. We pay attention to the three main topics -- validity of the rotating-wave approximation (RWA), pulse compression, and collisions of counter-propagating pulses. The cases of long and single-cycle pulses are considered and compared with each other. We show that the RWA does not give a correct description of chirped pulse interaction with the medium. The compression of the chirp-free single-cycle pulse is stronger than of the chirped one, while the opposite is true for long pulses. We demonstrate that the influence of chirp on the collisions of the long pulses allows to control the state of the transmitted radiation: the transmission of the chirp-free pulse can be dramatically changed under collision with the chirped counter-propagating one, in sharp contrast to the case when both pulses are chirped. On the other hand, the collisions of the chirped single-cycle pulses can be used for precise control of medium excitation in a narrow spatial region.