Over the past decade ion implantation has been demonstrated as a suitable technique for the fabrication of waveguide structures in an ever increasing number of optical materials. The stage has now been reached where actual device-oriented structures are being designed and implemented using this technology. This chapter will deal with the progress which is being made in the development of useful devices, and how ion implantation is being used to achieve these ends.

Many authors have recognised the advantages of waveguide structures for signal processing, for coupling to optical fibres or for frequency conversion. Optical circuitry has been proposed which, at least initially, was purely hypothetical, but has advanced to include ideas of entirely solid state waveguide structures (sometimes termed holosteric systems). Forseeable objectives include multi-frequency, or tunable, compact lasers in which the pump power is provided by a semiconductor diode. This inherently waveguide power source could then be matched into other waveguides for a combination of frequency conversion, SHG, pumping a tunable laser waveguide such as alexandrite or Ti:sapphire, or driving an optical parametric oscillator (OPO). The conversion efficiencies in the various stages are often as high as 30%, hence even in a several-stage process a 100 W semiconductor array could result in a few watts of tunable laser power. Such systems could of course supersede the highly inefficient Ar or Kr gas laser sources for many applications. The concepts are clear, and this final chapter will indicate how close the components are to realisation when using ion implantation fabrication routes.