Destructive Photon Echo Formation in Six‐Wave Mixing Signals of a MoSe₂Monolayer

Abstract

Monolayers of transition metal dichalcogenides display a strong excitonic optical response. Additionally encapsulating the monolayer with hexagonal boron nitride allows to reach the limit of a purely homogeneously broadened exciton system. On such a MoSe 2 -based system, ultrafast six-wave mixing spectroscopy is performed and a novel destructive photon echo effect is found. This process manifests as a characteristic depression of the nonlinear signal dynamics when scanning the delay between the applied laser pulses. By theoretically describing the process within a local field model, an excellent agreement with the experiment is reached. An effective Bloch vector representation is developed and thereby it is demonstrated that the destructive photon echo stems from a destructive interference of successive repetitions of the heterodyning experiment.

Controlled Coherent Coupling in a Quantum Dot Molecule Revealed by Ultrafast Four-Wave Mixing Spectroscopy

“…Note that this method directly probes the quantum coherence between the involved optically active states and therefore immediately demonstrates the quantum nature of the observed avoided crossing. Besides the coherent coupling, this spectroscopy method goes well beyond conventional (μPL) spetroscopy and can give valuable insight in the homogeneous broadening, , phonon-induced dephasing processes, or Rabi oscillations . Moreover, by changing the pulse powers, we can characterize the light–matter coupling strength (SI).…”

Controlled coherent-coupling and dynamics of exciton complexes in a MoSe2 monolayer

“…In this range the signal is retarded in time, such that the transient is not following the diagonal, and is instead curved, into a comet-like shape. The echo distortion is readily reproduced, when taking into account the local field effect [21], representing an effective exciton-exciton interaction, and is described in leading order in the local field coupling by…”

“…It even enables reaching the homogeneous limit for the exciton's spectral line shape [19,20]. This has been a milestone for monolayer spectroscopy, as it enhances the visibility of phenomena previously blurred by different types of inhomogeneity, with the appearance of a novel destructive photon echo being an example [21].…”

Coherent Dynamics of a Single Mn-Doped Quantum Dot Revealed by Four-Wave Mixing Spectroscopy

“…Even though the echo formation is commonly known for ensembles of emitters, it can also be generated for individual transitions. Here, the photon echo arises due to the exciton’s stochastic spectral wandering in time, accumulating into an effective inhomogeneous broadening of width σ in the time-averaged heterodyne experiment. ,,, To illustrate that, in Figure a we show the measured time-resolved FWM amplitude as a function of the time after the third pulse t and the delay τ 12 , while fixing τ 23 = 0. We observe that with increasing the delay τ 12 , the maximum of the signal shifts in time t along the diagonal τ 12 = t (dashed line).…”