In collaboration with Dr. John Love of the Optical Sciences Centre, the group was the first in Australia to design and fabricate optical planar waveguides Burried Channel Waveguides (BCW). The basic work is continuing with research into GRINN lenses for use in confocal microscopy and improvements into the fabrication of passive splitters for use in Local Area Networks.
New directions have opened up with the successful
commissioning of the HARE system which allows the doping of waveguides with
germanium, erbium, etc. These new devices will allow active and nonlinear
phenomena to be studied and provide the base technology for new
communication systems. We present the first report of an induced refractive index change in germano-silicate
glass containing no detectable levels of hydrogen. The single layer waveguide was
deposited on a silicon wafer by
Helicon Activated Reactive Evaporation, and following exposure to 193 nm UV from an
Excimer laser, an absolute decrease
of 0.006 in refractive index was measured. The dopant level of germanium is estimated
to be about 15% (mol).
Buried channel waveguides made of silica films deposited on silicon substrate have been fabricated at very low temperature (<100 degC) using helicon plasma assisted technique. Using the helicon plasma reactor for deposition and etching of the layers, we were able to perform all the fabrication steps at very-low temperature, below 100 degC.
Furthermore, thanks to the flexibility of the helicon plasma source, it is possible to control the energy of the ion bombardement impinging the surface during the deposition independently from the plasma generation, allowing an excellent control over the structure of the deposited material. The refractive index is controlled by fluorine doping, thus avoiding the use of poisonous gas such as germane or phosphine used in conventionnal PECVD technics. No nitrogen was introduced in the gas phase to avoid the absorption peak at 1.5 µm due to the N-H bonds commonly observed in PECVD deposited silica. We fabricated single mode BCW (at 1.3 µm and 1.55 µm), with a square core of 5 µm and n = (nco - ncl)/nco suitable for matching to optical fibre. The losses of the guides are of the order of 1 dB/cm.
A 1X8 concatenation of Y junctions under HeNe light illumination
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