Birefringence control in planar waveguides using doped top layers

By controlling layer thickness it is possible to achieve birefringence compensation within planar devices using a deposited top layer with higher thermal expansion than silica. The advantage of doped top layers allow very thin layers to be used for stress compensation, significantly reducing required deposition times. Further. fabrication methods different to that used to the principle method can be employed. Common materials able to be prepared using standard techniques are described. (C) 2001 Elsevier Science B.V. All rights reserved.