Second-Harmonic Generation in Bulk Diamond Based on Inversion Symmetry Breaking by Color Centers

TL;DR

This paper demonstrates second harmonic generation in bulk diamond by breaking inversion symmetry with nitrogen-vacancy centers, enabling second-order nonlinear optical effects previously limited in centrosymmetric diamonds.

Contribution

It introduces a method to induce second-order nonlinear effects in bulk diamond using color centers, specifically nitrogen-vacancy centers, enabling SHG in a material traditionally limited to third-order effects.

Findings

SHG and THG observed simultaneously in bulk diamond.

SHG acts as the source for THG via cascading process.

Symmetry breaking enables second-order NLO effects in centrosymmetric diamond.

Abstract

Breaking inversion symmetry in solids plays a central role in nonlinear optics because it can change material properties, such as producing even-order nonlinear optical (NLO) effects. Although a centrosymmetric diamond has been developed as a photonic platform, including waveguides and light sources, the NLO effects in bulk diamonds are limited to the third-order. Thus, exploiting more powerful second-order NLO effects, such as second harmonic generation (SHG), are still challenging. Here we explore symmetry-breaking-induced second-order NLO effects in bulk diamonds using the color center, nitrogen-vacancy center. Exciting with ultrashort laser pulses, SHG and third-harmonic generation (THG) are simultaneously observed at the same time, exhibiting characteristic intensity patterns, depending on both the excitation fluence and the angle of light polarization. We uncovered that SHG serves as the source for THG by the cascading process. Our findings will offer NLO effect-based quantum sensing by diamond color centers, such as imaging of the electromagnetic field by electro-optic effects on the nanofemto scale.