| 摘要 |
<p>A polarisation rotator (1) comprises a waveguide (2) formed on a silicon substrate, and a stress-inducing SiO2 layer (3) grown on top of the waveguide and having a series of discontinuities in the form of rectangular cutouts (4) which provide a periodically varying refractive index along the transmission axis of the waveguide. The cutouts (4) are produced during manufacture by stripping regions of the stress-inducing layer (3). The presence of the stress-inducing layer (3) causes the refractive index of the waveguide (2) to be subjected to a periodic perturbation which has the effect of producing some rotation of the polarisation at each transition between sections of different refractive indices so that, if the periodicity of these sections is appropriately set and an appropriate number of sections is provided, the rotations at successive transitions are added together in phase to provide the required polarisation rotation from one polarisation mode to another polarisation mode on transmission of the signal along the waveguide.</p> |
