TABLE OF CONTENTS Four areas have been covered in this final chapter. The first has been systems modelling where advanced numerical models can predict the performance of assemblages of devices all of which are modelled separately but can be brought together. It is believed that, as device modelling improves in accuracy, this area will grow extensively and it will reduce the costs of trying out new systems and speed up their design. The second area discussed is a specialist area where numerical modelling has led to a new device: the push ?pull laser. Even if this device does not become a production device, it highlights many mechanisms of importance within DFB lasers and illustrates how numerical modelling can aid invention.
The third and fourth areas are of growing importance. Tunable lasers or switchable laser systems will give WDM systems the versatility and flexibility they require. Which particular device or technique will win and become the industry standard for a WDM source is, at the time of writing, an open question. The final area of discussion is that of surface-emitting lasers and particularly VCSELs where the potential for growth in data processing and communications is vast. However, one recognises that there are serious challenges for designing and fabricating 1.55 ?m wavelength VCSELs where the desirable materials at present give too small a refractive-index step and the nonradiative Auger recombination can inhibit lasing unless low enough current densities are achieved. It is possible that full and detailed three-dimensional dynamic models of...
