UV written waveguides: applications in telecoms and sensors

In recent years, ultra-violet laser direct writing has been recognized as a technique that provides a powerful way of creating integrated optical devices. We will describe the developments in this field, concentrating on the use of two-beam writing to create Bragg gratings in planar integrated format. In this paper we will show how our UV writing technique can be used to fabricate structures required in a wide range of applications, from the creation of wide-band couplers, through to highly sensitive integrated sensor devices. The direct computer control in UV direct writing removes many of the constraints that normally limit planar integrated optics. In particular, it dispenses with the photolithography and etching steps traditionally required to make low-loss waveguide devices. The work reported will show how this flexibility of UV writing may be enhanced by using novel substrate structures that allow new device types. Results will be presented on Bragg grating sensors for solvent purity, biological layer measurement, phase changes and strain. Further results will include a demonstration of Liquid Crystal tuned Bragg grating devices yielding greater than 100GHz spectral tuning. Novel substrate configurations include a flat-fibre geometry based on MCVD fibre preform manufacture allowing devices with millimetre scale widths and 10s of cm lengths