Fabrication of optical waveguide taper couplers utilizing SiO_2

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Abstract
The fabrication of optical waveguide couplers involving tapered layers of is discussed. Details of the SiO2 photolithographic fabrication processing sequence are presented. This process utilizes carefully controlled etchant undercutting and has been found to be quite reproducible. It has allowed fabrication of tapers having changes in SiO2 thickness of 1.0 μm over lengths of 55–75 μm. Results are presented which demonstrate taper transverse uniformity for distances of over 600 μm. The smoothness and gradual nature of the tapers are apparent in scanning electron microscope pictures of a taper cross section.