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Recently, Nissan Chemical Industries, LTD, developed the photo-induced refractive index variation sol-gel materials, in
which the refractive index increases from 1.65 to 1.85 by ultra-violet (UV) light exposure and baking. The materials
enable us to fabricate high-index-contract waveguides without developing/etching processes and strong-lightconfinement
self-organized lightwave network (SOLNET). Therefore, the materials are expected promising for nanoscale
optical circuits with self-alignment capability. Nano-scale optical circuits with core thickness of ~230 nm and core
width of ~1 μm were fabricated. Propagation loss was 1.86 dB/cm for TE mode and 1.89 dB/cm for TM mode at 633
nm in wavelength, indicating that there were small polarization dependences. Spot sizes of guided beams along core
width direction and along core thickness direction were respectively 0.6 μm and 0.3 μm for both TE and TM mode.
Bending loss of S-bending waveguides was reduced from 0.44 dB to 0.24 dB for TE mode with increasing the bending
curvature radius from 5 μm to 60 μm. Difference in bending loss between TM and TE mode was less than 10%.
Branching loss of Y-branching waveguides was reduced from 1.33 dB to 0.08 dB for TE mode, and from 1.34 dB to
0.12 dB for TM mode with decreasing the branching angle from 80° to 20°. These results indicate that the photoinduced
refractive index variation sol-gel materials can realize miniaturized optical circuits with sizes of several tens
μm and guided beam confinement within a cross-section area less than 1.0 μm2 with small polarization dependences,
suggesting potential applications to intra-chip optical interconnects. In addtion, we fabricated self-organized lightwave
network (SOLNET) using the photo-induced refractive index variation sol-gel materials. When write beams of 405 nm
in wavelength were introduced into the sol-gel thin film under baking at 200°C, self-focusing was induced, and
SOLNET was formed. SOLNET fabricated by low write beam intensity exhibited strong light confinement.
Furthermore, SOLNET was found to be drawn automatically to reflective portion such as a defect and a silver paste
droplet in the sol-gel thin film during SOLNET formation, indicating that reflective SOLNET is formed. The results
suggest that the photo-induced refractive index variation sol-gel materials can provide self-alignment capability to the
nano-scale optical circuits.
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