Detuning-dependent narrowing of Mollow triplet lines of driven quantum dots

TL;DR

This paper analyzes how detuning affects the resonance fluorescence spectrum of driven quantum dots, revealing a complex interplay between detuning, dephasing, and spectral line narrowing or broadening.

Contribution

It provides analytical expressions for detuning-dependent damping and linewidth changes in Mollow triplet lines, highlighting the role of pure dephasing in these effects.

Findings

Detuning causes broadening of the central peak and narrowing of side peaks in the Mollow triplet.

Pure dephasing can invert the detuning dependence of spectral line widths.

The results align with recent experimental observations and numerical simulations.

Abstract

We study the two-time correlation function and the resonance fluorescence spectrum of a semiconductor quantum dot excited by a strong off-resonant laser pulse. The obtained analytical expressions exhibit a specific detuning-dependent damping of Rabi oscillations of the dressed quantum dot as well as a detuning-dependent width of Mollow-triplet lines. In the absence of pure dephasing, the central peak of the triplet is broadened, upon increasing detuning, but the blue and red side peaks are narrowed. We demonstrate that pure dephasing processes can invert these dependences. A crossover between the regimes of detuning-dependent narrowing and broadening of the side and central peaks is identified. The predicted effects are consistent with resent experimental results and numerical calculations.