Research Field: Physics
The global Internet traffic is increasing at an exponential rate. In the past, the transmission capacity of optical fibres has been scaled by adding more wavelengths channels and using complex modulation formats. However, this also requires larger optical powers, which cause greater optical nonlinearities. These optical nonlinearities result in an intrinsic capacity limit of common single-mode optical fibres, known as the nonlinear Shannon Limit. A promising approach to scale the transmission capacity is to utilise optical modes as individual, parallel data channels.
These modes are different intensity patterns, similar to the modes of a drum, which can propagate down the fibre. The challenge of this approach lies in generating and detecting the individual modes. Dr Gross has developed optical chips that can perform this task with high efficiency and fidelity. Unlike conventional optical chips that are based on a planar geometry, these chips rely on a 3D architecture, which mimics the transverse symmetry of the fibre modes. Thus a new technique had to be developed to access the third dimension. The technique uses a laser to induce a highly localised, but permanent structural modification inside glass. By moving the glass through the laser focus, arbitrary 3D optical circuits can be inscribed.