Tunable absorption spectrum splitting in a pulse-driven three-level system

TL;DR

This paper demonstrates how periodic pulse sequences can be used to control and modulate the absorption spectrum of a three-level quantum system, enabling tunable spectral features with minimal dependence on pulse carrier frequency.

Contribution

It introduces a method to modulate the absorption spectrum of a three-level system using periodic pulses, revealing tunable spectral splitting similar to Autler-Townes doublets.

Findings

Absorption spectrum shows Autler-Townes doublet with inter-pulse delay control.

Spectrum is largely independent of pulse carrier frequency.

Pulse-driven control enables spectral modulation in three-level systems.

Abstract

When a two-level system is driven on resonance by a strong incident field, its emission spectrum is characterized by the well-known Mollow triplet. If the absorption from the excited state, in this continuously driven two-level system, to a third, higher energy level, is probed by a weak field, the resulting absorption spectrum features the Autler-Townes doublet with two peaks separated by the Rabi frequency of the strong driving field. It has been shown that when the two-level system is instead driven by a periodic pulse sequence, the emission spectrum obtained has similarities with the Mollow triplet even though the system is only driven during the short application time of the pulses and is allowed to evolve freely between pulses. Here, we evaluate the absorption spectrum of the three-level system in the ladder/cascade configuration when the bottom two levels are driven by a periodic pulse sequence while the transition between the middle and the highest level is probed by a weak field. The absorption spectrum displays similarities with the Autler-Townes doublet with frequency separation between the main peaks defined by the inter-pulse delay. In addition, this spectrum shows little dependence on the pulse carrier frequency. These results demonstrate the capacity to modulate the absorption spectrum of a three-level system with experimentally achievable pulse protocols.