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Design and fabrication of waveguide structures on silicon-on-insulator (SOl) such as couplers and S-bends as components of Mach-Zehnder modulator (MZI) are presented here. These basic devices are important for processing light signals using silicon. Beam propagation method (BPM) was used to obtain dimensions of discussed structures for future manufacturing. During the design of the interferometer it was found that parameters of only either of branches could be altered to induce desired interference effect at the output of MZI. Hence, the device was dubbed unbalanced MZI. Since coupling separation was a factor that determines coupling length, it was chosen to be 1um in order to decrease overall length of the final structure and ensure that photolithography could be contained within the field size of the available steppers. The width for all waveguide components was chosen to be mm to accommodate photolithographic constraints as well. It was discovered that MEBES mask-writing tool produces field stitching. Features written across the boundary of two fields gaps produced notches that were expected to severely decrease the transmission of the l.55um light through the waveguides. New mask was sought and some devices were still built with the old mask to determine the viability of the proposed process.

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