Precision dicing and micromilling of silica for photonics

Abstract

This thesis focuses on the development of precision dicing and micromilling machining techniques for silica photonic applications. Comparison is given between the studied and conventional techniques for machining silica, such as photolithography and etching, laser machining, etc..
Precision dicing was used to create low loss input/output facets in the silica-on-silicon platform. It was demonstrated that ductile type dicing can produce facets in a silica-on-silicon substrate with a smooth, mirror like finish. The facet had a surface roughness (Sa) of 4.9 nm, a factor of ~7.5 improvement on previously reported roughnesses. An individual silica/air average interface loss, caused by surface roughness scatter, was calculated to be -0.63 dB and -0.76 dB for the TE and TM polarisations, respectively.
Utilising dicing, glass photonic microcantilever devices are produced with integrated Bragg gratings and waveguides. Two cantilever interrogations methods have been shown; one utilising a single Bragg grating and the other using a pair of spectrally matched Bragg gratings to form a Fabry-Pérot interferometer. These cantilever devices were subjected to physical stimulus of external pressure change and profilometer actuation.
A precision micromill was built by the author. Precision micromilling was used to remove the cladding material from the silica-on-silicon platform, for evanescent field access. By accessing the ductile milling regime, the mill enabled three-dimensional machining of flat, smooth, chip free grooves in silica. A groove with an average surface roughness (Sa) of 3.0 nm was measured, with a depth of cut of 17 µm. This micromilling method produces grooves that are seven times smoother and cut depths forty times deeper, than previously reported in the literature.

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Identifiers

ORCID for P.G.R. Smith: orcid.org/0000-0003-0319-718X

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