Strong Enhancement of Nonlinear Optical Properties Through Supramolecular Chirality

TLDR

The study introduces a new second‑order NLO material design that leverages chirality and supramolecular organization. The authors fabricate Langmuir‑Blodgett films of a chiral helicene, forming supramolecular arrays that underpin the material’s properties. Nonracemic films exhibit a second‑order NLO susceptibility about 30 times higher than racemic counterparts, reaching 50 pm V⁻¹, with chirality‑allowed components dominating the response.

Abstract

A new approach to second-order nonlinear optical (NLO) materials is reported, in which chirality and supramolecular organization play key roles. Langmuir-Blodgett films of a chiral helicene are composed of supramolecular arrays of the molecules. The chiral supramolecular organization makes the second-order NLO susceptibility about 30 times larger for the nonracemic material than for the racemic material with the same chemical structure. The susceptibility of the nonracemic films is a respectable 50 picometers per volt, even though the helicene structure lacks features commonly associated with high nonlinearity. Susceptibility components that are allowed only by chirality dominate the second-order NLO response.