# Manipulating Optical Nonlinearities of Molecular Polaritons by Delocalization

## TL;DR

This paper demonstrates control over vibrational polariton nonlinearities by adjusting macroscopic cavity parameters, enabling tunable optical responses relevant for IR photonics and chemical sensing.

## Contribution

It introduces a method to manipulate optical nonlinearities of molecular polaritons through macroscopic cavity parameters, a novel approach compared to chemical modifications.

## Key findings

- Nonlinearities last for the cavity mode lifetime.
- Nonlinearities evolve into dark reservoir responses.
- Control achieved via cavity length and molecular concentration.

## Abstract

Optical nonlinearities - how light-matter interactions are influenced by previous interactions with photons, are key resources in the contemporary photonics toolbox, relevant to quantum gate operations and all-optical switches. Optical nonlinearities of materials are often controlled at the microscopic level by chemical modification, which makes on-the-fly manipulation of such response challenging. Tunability of optical nonlinearities in the mid-IR is even less developed, hindering its applications in chemical sensing or IR photonic circuitry. Here, we report control of vibrational polariton coherent nonlinearities by manipulation of macroscopic parameters such as cavity longitudinal length or molecular concentration. These emergent nonlinearities last for the lifetime of the cavity mode, and subsequently evolve into the response determined by an incoherent population of dark reservoir modes. The observed phenomena arise due to the nonlinear macroscopic polarization stemming from strong coupling between microscopic molecular excitations and a macroscopic photonic cavity mode.

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Source: https://tomesphere.com/paper/1901.05526