Surface waveguides for telecom applications are typically SiO2-based, low-contrast surface waveguides because these
applications are dominated by the need for low optical attenuation and low polarization effects across the 1300-1600 nm
band. Conventional waveguides, however, comprise films as thick as 20 micron and have minimum bend radii of tens of
millimeters. These factors make conventional waveguide circuits large and expensive, and this has limited their use to
relatively few applications.
In the integrated optical sensing field, the waveguides typically used are (very) high-contrast waveguides. Here,
especially Si3N4-core waveguides are well-known to offer much smaller bending radii (tens to hundreds of microns)
due to stronger mode confinement to the core. Since they also typically comprise sub-micron core-thickness and
cladding-thickness of only a few microns, high-contrast waveguides promise lower cost than low-contrast waveguides.
Their use in telecom applications has been limited, however, due to strong polarization effects. Recently, LioniX, BV
has developed the TriPleXTM waveguide, which promises to be a well-suited platform for both telecom and sensing
applications and is based on low-cost, CMOS-compatible LPCVD processing. TriPleXtTM technology provides high-contrast
waveguides with very low channel attenuation and modal birefringence that is controlled through waveguide
design alone. Early experiments on typical geometries show promising waveguide characteristics (attenuation << 0.5
dB/cm, IL ≤ -2 dB, PDL << 1 dB, bend radius << 1 mm).
In this paper, we present the characteristics of this TriPleXTM technology, and show devices that have demonstrated
utility in telecom and/or sensor applications using medium and high-contrast waveguides. Experimental results for an
MZI-based sensor platform, suitable for liquid or gaseous sensing, are also provided.