Complex refractive index variation in proton-damaged diamond

TL;DR

This study systematically investigates how proton irradiation alters the complex refractive index of single crystal diamond, providing insights crucial for photonic device fabrication.

Contribution

It offers a detailed model linking damage density from proton implantation to changes in the real and imaginary parts of diamond's refractive index.

Findings

Refractive index variation correlates with damage density.

Laser interferometry effectively measures optical pathlength changes.

Spectrometric analysis reveals transmission modifications due to damage.

Abstract

An accurate control of the optical properties of single crystal diamond during microfabrication processes such as ion implantation plays a crucial role in the engineering of integrated photonic devices. In this work we present a systematic study of the variation of both real and imaginary parts of the refractive index of single crystal diamond, when damaged with 2 and 3 MeV protons at low-medium fluences (range: 10^15 - 10^17 cm^-2). After implanting in 125x125 um^2 areas with a scanning ion microbeam, the variation of optical pathlength of the implanted regions was measured with laser interferometric microscopy, while their optical transmission was studied using a spectrometric set-up with micrometric spatial resolution. On the basis of a model taking into account the strongly non-uniform damage profile in the bulk sample, the variation of the complex refractive index as a function of damage density was evaluated.