Highly integrated polymer photonic switching and interconnects

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Wang, Xiaolong

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Benefited from its tremendous gain in bandwidth, optics is taking the leader role instead of electronics in many communication systems for the past three decades, and is expected to continue this trend irresistibly in the predictable future. From the architecture point of view, most optical communication systems provide only the point-to-point topology. The interconnection among the distributed nodes still has to rely on the electronic exchanger, which is becoming an imminent bottleneck throttling the overall system bandwidth. In contrast, all optical exchange networks employing optical switches will skip the heavy-loaded data conversion and achieve a prominent bandwidth enhancement and cost reduction. In the first part of this dissertation, a planar lightwave circuit (PLC) based polymer optical switch utilizing total internal reflection (TIR) effect was proposed and fabricated. The optimized device obtained many desired features, such as low insertion loss, low cross talk, low power consumption and wavelength insensitivity. The application of the TIR optical switch was extended to provide true time delays (TTD) for phased array antennas (PAA). A fully integrated 4-bit TTD device composed of TIR switches and waveguide delay lines successfully delivered the 16 delay values required by a PAA system. As we move from long-distance network to short distance reach, optics encounters increasing difficulties in terms of packaging, reliability and system cost. However, with the rapid increasing speed and complexity of VLSI technology, electrical interconnects will fail to provide sufficient bandwidth beyond 10GHz after 2012. There does exist an opportunity for the continuing exploration of optics to complement or even replace the conventional board level electrical interconnects. An innovative approach with a fully embedded structure is anticipated to overcome the technical and cost barriers that prohibit the realization of optical interconnects in board levels. In the second half of this dissertation, technology efforts projected to relieve the concerns of low cost, high performance optical layers, as well as the system integration issues were carried out. The research accomplishments include a 51cm long molded waveguide array with 150GHz optical bandwidth, 85% coupling efficiency surface normal micro-mirror and system integration with laser diodes and photo detectors.