Multilayer single-mode polymeric waveguides by imprint patterning for optical interconnects

Low-loss single-mode waveguides are fabricated for optical interconnection applications. Such waveguides operating at telecom wavelength window are attractive for communicating between micro-photonic integrated circuit chips, such as silicon photonics, on the carrier/package, and also for enhanced coupling of photonic devices to fibers for longer reach interconnects. Manufacturing of the waveguides is based on direct pattering of optical polymeric materials by UV nanoimprinting. The advantages of the technology include the applicability to stack multiple layers of waveguides, fabrication on various substrate materials, and simultaneous fabrication of optical coupling structures. The developed process enables high wafer-level yield with precision overlay alignment. The multilayer waveguides were implemented using the so-called inverted rib waveguide process, that is, the shape of the waveguide cores are imprinted on the under-cladding layer as grooves and then the core material is deposited on the cladding layer filling the grooves and also forming a thin slab layer. The subsequent deposition of the upper cladding layer finalizes the first waveguide layer and also starts the manufacturing of the next waveguide layer. The achieved wafer-scale layer-to-layer alignment tolerances were 1... 2 mu m and < 0.3 mu m in horizontal and vertical directions, respectively. Losses measured from the long waveguide spirals made of commercial ORMOCER materials on silicon wafers were 0.35 dB/cm at 1305 nm and 0.86 dB/cm at 1530 nm, which are only around 0.15 dB/cm higher than the material losses.