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Proceedings Paper

Nano-scale optical circuits and self-organized lightwave network (SOLNET) fabricated using sol-gel materials with photo-induced refractive index increase
Author(s): Shigeru Ono; Tetsuzo Yoshimura; Tetsuo Sato; Juro Oshima
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Paper Abstract

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.

Paper Details

Date Published: 12 February 2009
PDF: 12 pages
Proc. SPIE 7221, Photonics Packaging, Integration, and Interconnects IX, 722109 (12 February 2009); doi: 10.1117/12.807603
Show Author Affiliations
Shigeru Ono, Tokyo Univ. of Technology (Japan)
Tetsuzo Yoshimura, Tokyo Univ. of Technology (Japan)
Tetsuo Sato, Nissan Chemical Industries, Ltd. (Japan)
Juro Oshima, Nissan Chemical Industries, Ltd. (Japan)

Published in SPIE Proceedings Vol. 7221:
Photonics Packaging, Integration, and Interconnects IX
Alexei L. Glebov; Ray T. Chen, Editor(s)

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