RESUMO
Luminescence microscopy is used to measure the refractive index profile and molecular defect distribution of UV written waveguides with a spatial resolution of ~0.4 ?m and high signal-to-noise ratio. The measurements reveal complex waveguide formation dynamics with significant topological changes in the core profile. In addition, it is observed that the waveguide formation process requires several milliseconds of UV exposure before starting.
RESUMO
A behavior is reported where the index change process used for UV writing of integrated optical waveguides in deuterium loaded Ge:SiO2 glass can become unstable and suddenly switch off or on. It is shown that such discontinuities are associated with abrupt changes in the amount of absorbed UV power. We suggest that these events are controlled by a coupling between UV absorption, local heating and the D2-GeO2 reaction rate. From our findings we predict, and confirm experimentally, that strong waveguides can not be fabricated under normal UV writing conditions in thin core layers with a low initial UV absorption. Our findings show that an improved understanding of the waveguide formation process and future process development requires that thermal effects are taken into account.
RESUMO
We present an empirical model for the waveguiding properties of directly UV-written planar waveguides in silica-on-silicon. The waveguides are described by a rectangular core step-index profile, in which model parameters are found by comparison of the measured waveguide width and effective index with modal field calculations. The model is used as input for beam propagation method calculations to design UV-written optical components. Subsequent fabrication of such components showed a good agreement with the model predictions. Using the model will reduce the number of iterations and thereby the development time of new optical devices.
