Large optical nonlinearity enhancement under electronic strong coupling

Kuidong Wang,Cyriaque Genet,Marcus Seidel,Kalaivanan Nagarajan,Thomas Ebbesen,Thibault Chervy

doi:10.1038/s41467-021-21739-7

Abstract

Nonlinear optical responses provide a powerful way to understand the microscopic interactions between laser fields and matter. They are critical for plenty of applications, such as in lasers, integrated photonic circuits, biosensing and medical tools. However, most materials exhibit weak optical nonlinearities or long response times when they interact with intense optical fields. Here, we strongly couple the exciton of cyanine dye J-aggregates to an optical mode of a Fabry-Perot (FP) cavity, and achieve an enhancement of the complex nonlinear refractive index by two orders of magnitude compared with that of the uncoupled condition. Moreover, the coupled system shows an ultrafast response of ~120 fs that we extract from optical cross-correlation measurements. The ultrafast and large enhancement of the optical nonlinar coefficients in this work paves the way for exploring strong coupling effects on various third-order nonlinear optical phenomena and for technological applications.

Highlights

Nonlinear optical responses provide a powerful way to understand the microscopic interactions between laser fields and matter
The third-order optical nonlinear responses of a material can be described by two parameters, the nonlinear refractive index n2 and nonlinear absorption coefficient β
Our strongly coupled system (ESC cavity) was realized by placing J-aggregates of cyanine molecules dispersed in a polyvinyl alcohol (PVA) polymer inside a planar silver FP cavity

Summary

Introduction

Nonlinear optical responses provide a powerful way to understand the microscopic interactions between laser fields and matter. The ultrafast and large enhancement of the optical nonlinar coefficients in this work paves the way for exploring strong coupling effects on various third-order nonlinear optical phenomena and for technological applications. Such limitations call for alternative strategies in order to improve the nonlinear responses of existing materials One such strategy is to exploit the effects of light-matter strong coupling on materials’ optical responses. This can be achieved by coupling an excitonic transition and a resonant optical mode of a cavity and when the energy exchange between them is faster than the timescales associated with all dissipative and incoherent processes, two new exciton-polaritonic states are generated, separated in energy by the so-called Rabi splitting (Fig. 1a). This result demonstrates how ESC can meet the essential requirements for ultrafast optical modulation and data processing

Methods

Results

Conclusion