The appeal of small molecules for practical nonlinear optics

TL;DR

Small conjugated organic molecules with donor-acceptor groups exhibit significantly enhanced third-order nonlinear optical properties, enabling practical applications in integrated photonics due to their large polarizabilities and processability.

Contribution

This paper highlights the potential of small donor-acceptor conjugated molecules to achieve large nonlinear optical responses, advancing the development of practical nonlinear optical materials.

Findings

Third-order nonlinear polarizabilities can be up to 1000 times larger than in similar-sized molecules without donor-acceptor groups.

These molecules enable strong nonlinear effects in dense, amorphous assemblies.

Materials can be deposited from vapor and electrically poled at high temperatures, suitable for integrated photonics.

Abstract

Small organic molecules with a {\pi}-conjugated system that consists of only a few double or triple bonds can have significantly smaller optical excitation energies when equipped with donor- and acceptor groups, which raises the quantum limits to the molecular polarizabilities. As a consequence, third-order nonlinear optical polarizabilities become orders of magnitude larger than those of molecules of similar size without donor-acceptor substitution. This enables strong third-order nonlinear optical effects (as high as 1000 times those of silica glass) in dense, amorphous monolithic assemblies. These properties, accompanied by the possibility of deposition from the vapor phase and of electric-field poling at higher temperatures, make the resulting materials competitive towards adding an active nonlinear optical or electro-optic functionality to state-of-the-art integrated photonics platforms.