Abstract
This paper presents work aimed at optimizing the fabrication of silicon nitride Si(x)N(y) thin-film visible-light planar waveguides using plasma-enhanced chemical vapour deposition (PECVD). The effects of plasma frequency, precursor gas ratio, and thermal annealing in relation to waveguide optical properties (refractive index, propagation losses) are studied. Experimental results over a wide range of precursor gas ratios show convincingly that waveguides fabricated using low-frequency PECVD have lower propagation losses in the visible range compared to waveguides of equal refractive index fabricated with high-frequency PECVD.
Highlights
Dielectric thin films having a high refractive index are used more and more in optics and optoelectronics, especially for interference filters, coatings and waveguides
Low-loss (< 1dB/cm) optical waveguides for the visible range have been fabricated with Si3N4 using low-pressure chemical vapour deposition (LPCVD) [6]
For the fabrication of optical components such as waveguides, filters, etc., the results presented in Figs. 1 and 2 demonstrate that thin films deposited with LF-plasma-enhanced chemical vapour deposition (PECVD) have better optical properties over the visible range
Summary
Dielectric thin films having a high refractive index are used more and more in optics and optoelectronics, especially for interference filters, coatings and waveguides. In addition to a high refractive index, fluorescence-based biosensors require optical waveguiding materials having low propagation losses over the visible and near-IR range. Often, such materials must be deposited on a glass substrate, requiring low temperature microfabrication processes (< 400°C) [4, 5]. Though a small number of studies on the correlation between absorption in silicon nitride PECVD films and NH3/SiH4 ratio have been reported [13,14], there are no existing publications on the optimization of PECVD fabrication parameters, such as plasma composition, with regards to losses in the visible range for SixNy thin-film optical waveguides. The performance of SixNy optical waveguides, fabricated both with LF-PECVD and HFPECVD, are compared
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