We demonstrate theoretically and experimentally how highly multimodal high index contrast waveguides with micron-scale cores can be bent, on an ultra-broad band of operation, with bending radii below 10 µm and losses for the fundamental mode below 0.02 dB/90°. The bends have been designed based on the Euler spiral and fabricated on 4 µm thick SOI. The proposed approach enabled also the realization of 180° bends with 1.27 µm effective radii and 0.09 dB loss, which are the smallest low-loss bends ever reported for an optical waveguide. These results pave the way for unprecedented integration density in most semiconductor platforms.

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We report, to the best of our knowledge, the first experimental proof of MMI-based resonators. The resonators have been designed and fabricated on a micron-scale silicon photonics platform and are based on different reflectors suitably placed on two of the four ports of 2x2 MMIs with uneven splitting ratios, namely 85:15 and 72:28. The reflectors are either based on aluminum mirrors or on all-dielectric MMI mirrors. Performances of the different designs are compared with each other and with numerical simulations. Finesse values as high as 13.1 (9.9) have been measured in best aluminum (all-dielectric) resonators, corresponding to a quality factor of 5.8·10(3) (12.5·10(3)) and mirror reflectivity exceeding 92% (88%).

We report on the simultaneous wavelength conversion operation of a dual-element semiconductor optical amplifier-Mach-Zehnder interferometer (SOA-MZI) array hybridly integrated on a 4-µm silicon-on-insulator (SOI) waveguide platform through thermocompression bonding. The SOAs are part of a six-element SOA array with both facets coupled on SOI through vertical and horizontal alignments. The device achieves almost two orders of magnitude reduction in footprint compared with state-of-the-art hybridly integrated SOA-MZI structures. We present for the first time experimental proof of the successful operation of a dual-element SOA-MZI device based on III-V technology on SoI that serves as a wavelength converter, with one SOA-MZI yielding error-free performance with a 0.8-dB power penalty at 12.5 Gb/s and the second SOA-MZI operating error-free at 10 Gb/s with a 2-dB power penalty.Index Terms-Mach-Zehnder interferometer, semiconductor optical amplifier, wavelength conversion, hybrid integration, thermocompression bonding, dual-facet coupling.

A novel guided-wave optical power coupler is presented, based on two 2x2 50/50 multimode interference splitters connected with tapered waveguides that play the role of a phase shifter. By simply changing the length of this phase shifter, these double-MMI couplers can be easily designed to get any desired splitting ratio. Results of simulations are discussed and compared with the characterizations of devices fabricated on micron-scale SOI wafers, to highlight pros and cons of the proposed solution. The fabricated splitters have been found to have average losses about 0.4 ± 0.5 dB and splitting ratios ranging from 56/44 to 96/4.

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