| Abstract | InP/InGaAsP weakly confined wave guides, are of interest for the fabrication of a variety of optoelectronic devices, including optical cross point switches. Previous studies have shown that stress from metallization alters the behavior of these waveguides and the strain-induced changes in refractive index have been investigated by studying the degree of polarization (DOP) from the facets of ridge waveguide (RWG) lasers. However, in devices intended for waveguide routing or switching, (where the degree of confinement is much weaker than that found in ridge waveguide lasers), e-beam deposited TiPtAu contacts, caused broadening and splitting of the optical near field mode profile after thermal annealing and increased waveguide loss. In this paper, we report the results of a study of process-induced changes on the optical near field mode profile, for different dielectric depositions, metalizations and anneal cycles. It was found that the addition of a layer of sputtered W to the e-beam metal stack provided sufficient compressive stress to balance the (otherwise) tensile stress from the TiPtAu. This not only eliminated the mode splitting, but for sufficiently high values of compressive stress, was found to actually sharpen the mode and enhance the guiding. On the basis of these results stable waveguides, suitable for routing or switching were achieved for a range of device parameters, operating conditions and process parameter variations. |
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