For centuries diamond has been highly sought after for manufacture into gem stones; the demand stems from its exemplary physical properties. Its visual appeal is a consequence of its optical characteristics: its rigid lattice is insusceptible to impurities leading to wide transparency; a high refractive index leads to strong reflections; and trace inclusions can lead to striking uniform colours. Beyond the gem trade, many technical and industrial applications rely upon diamond for its mechanical hardness, thermal characteristics or low electrical conductivity. Other advantages include a high degree of biocompatibility, rendering it useful in biological studies.
Diamond’s remarkable characteristics make it a promising medium for many optical devices, since it is ideal for structures allowing light manipulation on small scales across a broad spectrum. Colour centres formed by inclusions or vacancies in diamond’s crystal structure are being used as tools in quantum optics, opening up numerous possible applications of quantum-enhanced technologies. Recent breakthroughs in the manufacture of affordable high-grade synthetic (man-made) diamond substrates are fuelling interest for such photonic applications in diamond.
Our laser fabrication capabilities allow the simultaneous generation of multiple confined features embedded within diamond (left). Our expertise in adaptive optics means we can counter problems associated with focussing in diamond to maintain accurate fabrication deep within diamond (right). We aim to combine these skills for the creation of photonic devices that manipulate light (bottom).
The full potential of diamond-based devices in photonics can only be achieved through the ability to create and fully characterise optical-wavelength scale 3D structures in diamond. We are proposing a method that would introduce true 3D fabrication in this area. Our tool is a high power laser whose energy is delivered in a series of extremely short pulses (each less than a millionth of a millionth of a second in duration). By tight focussing of the laser beam into the diamond we are able to create highly localised small (sub-micron) features deep within the diamond. This is only made possible through the use of adaptive optics, which allows us to compensate for optical distortions induced by refraction at the surface of the diamond. It also allows us to generate multiple features simultaneously all with just a single pulse from the laser, significantly reducing processing times.
The funding from the Leverhulme Trust is allowing us to fully explore the exciting potential of our fabrication capabilities in diamond. This will enable the manufacture of devices for optical manipulation, but will also provide opportunities for the production and analysis of electrical circuits embedded in the diamond. Our improved understanding of focussing into diamond is also expected to benefit many other research fields, such as geology where the study of natural diamond provides clues as to the conditions in the Earth’s mantle when they were formed.
Dr Martin Booth
University of Oxford
Dr Booth was awarded a Leverhulme Trust Research Project Grant in March 2013.