Coherent Dynamics in Quantum Emitters under Dichromatic Excitation

TL;DR

This paper investigates the coherent dynamics of quantum emitters under dichromatic excitation, revealing how spectral overlap and additional interactions influence population inversion and enabling background-free photon extraction.

Contribution

It demonstrates that asymmetric dichromatic excitation can enhance population inversion and background-free photon emission, supported by experimental and simulation results.

Findings

Symmetric driving leads to limited inversion (~50%) due to pulse area cancellation.

Asymmetric excitation improves inversion efficiency by adjusting pulse intensities.

Coupling to lattice vibrations influences the inversion dynamics.

Abstract

We characterize the coherent dynamics of a two-level quantum emitter driven by a pair of symmetrically-detuned phase-locked pulses. The promise of dichromatic excitation is to spectrally isolate the excitation laser from the quantum emission, enabling background-free photon extraction from the emitter. Paradoxically, we find that excitation is not possible without spectral overlap between the exciting pulse and the quantum emitter transition for ideal two-level systems due to cancellation of the accumulated pulse area. However, any additional interactions that interfere with cancellation of the accumulated pulse area may lead to a finite stationary population inversion. Our spectroscopic results of a solid-state two-level system show that while coupling to lattice vibrations helps to improve the inversion efficiency up to 50\% under symmetric driving, coherent population control and a larger amount of inversion are possible using asymmetric dichromatic excitation, which we achieve by adjusting the ratio of the intensities between the red and blue-detuned pulses. Our measured results, supported by simulations using a real-time path-integral method, offer a new perspective towards realising efficient, background-free photon generation and extraction.