Diamond Based Optical Components for High Power Laser Applications

Abstract

Diamond is a particularly attractive material for nanoscale technologies and bulk optics due to its exceptional material properties. Optically, diamond has a relatively high refractive index (2.4) and a wide bandgap of 5.5eV leading to a large optical transmission window from the UV well into the mid infrared. Beyond its optical properties, diamond has impressive physical and chemical properties, resulting in high mechanical hardness, chemical inertness and remarkably high thermal conductivity. Diamond is also host to numerous defect color centers useful in the area of quantum optics as single photon sources. Commercially available diamond-on-insulator products provide wafer scale nanocrystalline diamond films on sacrificial substrates such as SiO2, but due to grain boundaries, interfacial stress and poor surface roughness, this platform remains unsuitable for demanding photonic applications looking to benefit from the full potential of diamond’s extraordinary material properties. In lieu of heteroepitaxial single crystal diamond films, significant progress has been made to create cutting edge photonic structures from bulk single crystal diamond. In this thesis, we present recent contributions where we demonstrate wafer-scale processing for realizing freestanding nanoscale photonic structures. Reactive ion beam etching is utilized to create a fabrication procedure where a collimated ion beam using oxygen gas is used to undercut nanoscale structures creating freestanding photonics devices etched from a bulk diamond. The novelty of this approach is the true wafer scale processing providing us with uniform photonic structures across a large area. This fabrication technique will be referred to as reactive ion beam undercut etching (RIBUE). Next, we present superconducting nanowire single photon detectors (SNSPD) deposited on diamond substrates, exhibiting similar performance to detectors grown on traditional substrates such as SiO2, MgO or sapphire. We develop a procedure for deterministic placement of silicon vacancy (SiV) defect color centers in free-standing diamond nanobeam waveguides using focused ion beam implantation. Ultimately, we fabricate freestanding diamond waveguides, where photon emission from implanted color centers are directed towards evanescently coupled SNSPDs. Lastly, we utilize the RIBUE wafer scale fabrication technique to create an all-diamond high reflectivity metasurface mirror etched from a bulk diamond substrate. The optical properties of the metasurface are engineered by novel nano-structuring of the diamond surface, while simultaneously capitalizing on the high thermal conductivity inherent to bulk single crystal diamond. The end result is a robust mirror with exceptional optical properties that can withstand extremely high laser power intensities that would otherwise damage traditional multi-layered optical coatings.