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Polymer materials are generally recognized to exhibit various favorable
properties for the use in optical waveguide technology. There is
a great potential for the use of polymers in terms of optical properties,
cost-effectiveness, and processing possibilities. Optical polymers
are versatile materials that can be readily formed into planar single-mode
and multimode waveguides. With regard to optical interconnect applications
polymers have to fulfill tight requirements, such as very low optical
losses and the compatibility with printed circuit board manufacturing
processes (e.g. resilience against solder reflow and lamination
process).
The optical propagation distance we anticipate is in the range
of 30 to 100 cm and therefore the propagation losses should be below
0.05 dB/cm. Allowing for these low losses and the required compatibility
with PCB manufacturing, we evaluated different photosensitive polymer
materials that are mainly based on acrylates and siloxanes. The
deposition of the liquid polymeric layers as claddings and waveguide
cores on conventional FR4 substrates was done by doctor blading
as well as by spray coating. The patterning of the core layer was
performed by laser direct writing or photolithography and subsequent
wet-chemical developing.
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