Quantum interference between the optical Stark effect and resonant harmonic generation in WS2

TL;DR

This paper explores how the optical Stark effect influences resonant harmonic generation in WS2, revealing complex behaviors and a new manifestation involving coherent photon exchange that can enhance or suppress harmonic signals.

Contribution

It demonstrates the interplay between the optical Stark effect and harmonic generation in WS2, introducing a new manifestation involving coherent photon exchange that affects harmonic intensity.

Findings

Large Stark shifts observed in WS2 excitons.

Complex behaviors beyond simple Stark effect models.

Coherent photon exchange can enhance or suppress harmonic generation.

Abstract

An applied field can modulate optical signals by resonance shifting via the Stark effect. The optical Stark effect (OSE) uses ultrafast light in the transparency region of a material to shift resonances with speeds limited by the pulse duration or system coherence. In this Letter we investigate the OSE in resonant optical harmonic generation (OHG) using the ground state exciton transition of WS2 with a variety of morphologies. Multidimensional pump-harmonic-probe measurements, in which the probe is second- or third-harmonic emission, reveal not only large Stark shifts that are commensurate with the large optical susceptibilities common to WS2 excitons, but also behaviors more complex than simple OSE treatments predict. We show how a new manifestation of the Stark Effect, brought forth by coherent photon exchange between the pump and OHG fundamental fields, can strongly enhance or suppress OHG.