Alloy Engineering of Polar (Si,Ge)2N2O System for Controllable Second Harmonic Performance

TL;DR

This study explores silicon oxynitride's potential for nonlinear optical applications, demonstrating alloying with germanium to control second-harmonic generation properties for tunable optical devices.

Contribution

It introduces alloy engineering in Si2N2O to controllably tune second-order nonlinear optical properties, supported by first-principles calculations and preliminary experiments.

Findings

Si2N2O exhibits wide bandgap, strong SHG, and birefringence.

Alloying Ge into Si2N2O forms stable alloys with controllable NLO properties.

High SHG efficiency achieved at various energy ranges.

Abstract

Although silicon oxynitrides are important semiconductors for many practical applications, their potential second-order nonlinear optical (NLO) applications, regardless of balanced or controllable performance, have never been systemically explored. Using the first-principles calculations, in this article, we discover that the sinoite (i.e., typical silicon oxynitride Si2N2O) can simultaneously exhibit wide optical bandgap, strong second-harmonic generation (SHG) effect, and large birefringence, which are further confirmed by our preliminary experimental data. Importantly, we propose that alloying engineering can be further applied to control the balanced NLO properties in the Si2N2O system. Combining first-principles calculations and cluster expansion theory, we demonstrate that alloying Ge into Si2N2O can easily form low formation energy Si2(1-x)Ge2xN2O alloys, which can in turn achieve controllable phase-matching harmonic output with high SHG efficiency at different energy ranges. Therefore, alloy engineering could provide a unique approach to effectively control the balanced NLO performance of Si2(1-x)Ge2xN2O, making this polar alloy system holding potential applications in tunable laser frequency conversion and controllable all-optical devices.