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29 July 1997 Polyimide-based waveguides for guided-wave multi-Gbit/sec MCM optoelectronic interconnects
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We present the fabrication of polyimide-based H-tree waveguides for a multi-GBit/sec optical clock signal distribution in a Si CMOS process compatible environment. Such a clock distribution system is to replace the existing electronic counterpart associated with high-performance computers. A waveguide propagation loss of 0.21 dB/cm at 850 nm was experimentally confirmed for the l-to-48 waveguide fanout device, l-to-2 splitting loss and bending loss were measured to be 0.25 dB and higher. The planarization requirement of the optical interconnection layer among many electrical interconnection layers makes the employment of tilted grating a choice of desire. Theoretical calculation predicts the 1-to-l free-space to waveguide coupling with an efficiency as high as 95%. Currently, a coupling efficiency of 35% was experimentally confirmed due to the limited index difference between guiding and cladding layers. Further experiments aimed at structuring a larger guiding/cladding layer index differences are under investigation. To effectively couple an optical signal into the waveguide through the tided grating coupler, the accuracy of the wavelength employed is pivotal. This makes the usage of the vertical cavity surface-emitting lasers (VCSELs) and VCSEL arrays the best choice when compared with edge-emitting lasers. Modulation bandwidth as high as 6 GBit/sec was demonstrated at 850 nm. Such a wavelength is compatible with Si-based photodetectors. Temperature dependence of the threshold current up to 155 °C was measured which will determine the power dissipation issue of the optoelectronic packaging. Finally, the first fully monolithic Si-MOSFET integrated receiver was made as the optical clock signal detector. To further enhance the bandwidth of such a detector, a resonant cavity structure with Si/Si02 as the bottom mirror was employed. The measured demodulation bandwidth is over 10 GHz. A fully integrated guided-wave optical clock signal distribution system having planarized grating couplers, H-tree Si- CMOS process compatible waveguides, VCSELs and Si-based photo-receivers will be demonstrated in the near future.
© (1997) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Ray T. Chen, Linghui Wu, Feiming Li, Suning Tang, Michael Dubinovsky, J. M. Qi, Clint L. Schow, Joe C. Campbell, Randy W. Wickman, Bruce R. Pecor, Mary K. Hibbs-Brenner, Julian P. G. Bristow, Yung-Sheng Liu, Scott Rattan, and Chad Noddings "Polyimide-based waveguides for guided-wave multi-Gbit/sec MCM optoelectronic interconnects", Proc. SPIE 10290, Sol-Gel and Polymer Photonic Devices: A Critical Review, 102900M (29 July 1997);


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