Propagation of subcycle pulses in a two-level medium: Area-theorem breakdown and pulse shape

TL;DR

This paper investigates ultrashort subcycle pulse propagation in a two-level medium beyond common approximations, revealing breakdown of the area theorem for large-area pulses and shape-dependent deviations.

Contribution

It introduces a unified numerical method to analyze ultrashort pulse propagation beyond RWA and SVEA, highlighting shape-dependent effects on the area theorem breakdown.

Findings

Breakdown of the area theorem occurs for large-area subcycle pulses.

Deviations from the area theorem depend strongly on pulse shape.

The method allows switching between RWA and non-RWA cases in a single framework.

Abstract

We solve the problem of ultrashort pulse propagation in a two-level medium beyond the rotating-wave (RWA) and slowly-varying-envelope approximations. The method of solution is based on the Maxwell--Bloch equations represented in the form that allows one to switch between RWA and general (non-RWA) cases in the framework of a single numerical algorithm. Using this method, the effect of a subcycle pulse (containing less than a single period of field oscillations) on the two-level medium was analyzed. It is shown that for such short pulses, the clear breakdown of the area theorem occurs for the pulses of large enough area. Moreover, deviations from the area theorem appear to be strongly dependent on the pulse shape that cannot be observed for longer few-cycle pulses.