12 on/off power splitters at λ=0.63µm have been produced in LiNbO3 substrates using strain-induced channel waveguides formed by magnetron deposition of surface metal films and lift-off technology. The static strain resulting from thermal expansion mismatch between the substrate and the metal films induces a localized increase in the refractive index via the strain-optic effect. On/off voltage of about 25V has been demonstrated.

Extremely compact multi-mode interference (MMI) devices using central wide-angle coupling of input and output waveguides are proposed. It is shown that MMI can be used to change the propagation direction of light without the need for corner mirrors or bent waveguides. The concept can also be used for very compact power splitters which are even smaller than conventional MMI power splitters. Coupling between waveguides at wide angles is discussed and a number of regularities are found. The results can be useful for the design of more compact integrated circuits by a reduction of the number of bent waveguides which usually take up the largest part of the area of a photonic integrated circuit.