In recent years experiments have shown that optical waves in waveguides can be modulated by mechanical stresses from surface acoustic waves (SAW), which have most of their energy density concentrated at the surface. In these experiments the SAWs are generated in piezoelectric materials by conventional interdigital transducers consisting of thin electrodes deposited at the surface. In this work the finite element method is employed to investigate if the acousto-optical interaction can be enhanced by generating the SAWs by interdigital transducers consisting of high aspect ratio electrodes. With a periodic model it is first shown that these tall electrodes introduce several new confined SAW modes with slow phase velocities because of mechanical energy storage in the electrodes. The periodic model is then extended to a finite model by using perfectly matched layers at the substrate borders and is furthermore coupled to an optical model of the light in an optical waveguide at the substrate surface. By calculating the SAW introduced change in effective refractive index, which is a measure of the acousto-optical interaction, it is shown that the interaction is increased more than 300 times using these new types of SAWs compared to using the waves generated by the conventional interdigital transducer with thin electrodes. Thus, this indicates a way to improve acousto-optical interaction for integrated modulators, which have important applications such as optical phase shifters.
|Publication status||Published - 2009|
|Event||DCAMM 12th International symposium - Sørup Herregård, Ringsted, Denmark|
Duration: 1 Jan 2009 → …
Conference number: 12
|Conference||DCAMM 12th International symposium|
|City||Sørup Herregård, Ringsted, Denmark|
|Period||01/01/2009 → …|