Femtosecond Laser Writing Inside Diamond

Laser writing with pulses of duration less than a picosecond presents a diverse platform for the functionalisation of diamond, with a range of different modification regimes for internal structuring beneath the diamond surface. The laser is tightly focused beneath the surface where non-linear absorption leads to a perturbation of the diamond structure on a scale less than a micrometre, without any damage to the surrounding material or surface. At higher laser pulse energy, the light-matter interaction breaks down the diamond to create a graphitic phase. At lower laser pulse energy, a finer process is accessible which can yield a vacancy ensemble, without breakdown of the diamond lattice. These processing regimes are applied for the fabrication of a range of devices, ranging from detectors for harsh environments, through to quantum technology and security inscription within gemstones.<br/>We focus this talk on our new results for laser written vias passing through a diamond wafer, and the influence of laser dose on the electrical conductivity. Surprisingly, increasing the laser dose delivered to the sample causes a transition from a regime in which the written structures display ohmic conductivity into a regime which in which they are insulating in nature. We show that a combination of these regimes can be achieved with laser over-writing to give asymmetric conduction characteristics for the vias. A high-resolution structural characterisation of the laser written features by transmission electron microscopy reveals a diverse range of carbon nanostructures embedded within the diamond, and can be used to explain some of these phenomenon