Electric Field Effect on Optical Second-harmonic Generation of Amphoteric Megamolecule Aggregates

TL;DR

This study investigates how electric fields influence the second-harmonic generation in amphoteric sacran mega-molecules, revealing field-dependent nonlinear optical responses and molecular orientation effects.

Contribution

It demonstrates electric field control of SHG in amphoteric sacran aggregates and provides insights into their charge-induced nonlinear optical properties.

Findings

SHG observed near negatively biased needle electrode below -4.5 V

Sacran molecules oriented toward the electrode needle

SHG induced by positively charged sacran aggregates

Abstract

We have detected second-order nonlinear optical response from an amphoteric mega-saccharides named sacran under a needle/ring electrode stimulus by using an optical second harmonic generation (SHG) microscope. SHG was observed from sacran in the neighborhood of the negatively biased needle electrode below -4.5 V with respect to the outer ring electrode. From the incident light polarization dependence of SHG, this sacran was suggested to be oriented toward the electrode needle. SHG of the sacran polymer was judged to be induced by sacran aggregates with net positive charge.