Tailoring the optical constants of diamond by ion implantation

We study the effect of 30 keV gallium ion implantation on the optical properties of diamond, as determined using spectroscopic ellipsometry. We find that the refractive index of the implanted layer can be either lower, or higher, than that of pristine diamond, depending on the implantation dose. This observation provides a new route to optical device fabrication in diamond using focused ion beam methods. In particular, in the low dose regime, lowering of the refractive index would allow for core-cladding type structures to be defined where the core has not interacted with the beam, and is hence undamaged by the implantation.