Emergence of structural anisotropy in Optical Glasses treated to support Second Harmonic Generation

TL;DR

This study reveals that thermal poling induces structural anisotropy in v-SiO2 glass, leading to partial ordering and changes in vibrational properties, which enhances its nonlinear optical capabilities like second harmonic generation.

Contribution

It demonstrates the structural basis for second harmonic generation in optical glasses through neutron diffraction and scattering analysis of thermally poled v-SiO2.

Findings

Breakdown of isotropy in v-SiO2 after poling

Emergence of partial ordering along the electrostatic field

Alterations in vibrational density of states

Abstract

Structural alterations in v-SiO2 induced by "thermal poling", a treatment which makes the glass able to double the frequency of an impinging infrared light, are revealed by neutron diffraction as a breakdown of the macroscopic isotropy. This leads to concomitant changes in the vibrational density of states measured by inelastic neutron scattering. The observations are found to be consistent with the emergence of partial ordering within the glassy matrix along the direction of an electrostatic field applied during the poling treatment.