Design, fabrication and characterisation of nano-imprinted single mode waveguide structures for intra-chip optical communications

In the Information and Communications Technology (ICT) sector, the demands on bandwidth continually grow due to increased microprocessor performance and the need to access ever increasing amounts of stored data. The introduction of optical data transmission (e.g. glass fiber) to replace electronic transmission (e.g. copper wire) has alleviated the bandwidth issue for communications over distances greater than 10 meters, however, the need has arisen for optical data transfer over shorter distances such as those found inside computers. A possible solution for this is the use of low–cost single mode polymer based optical waveguides fabricated by direct patterning Nanoimprint Lithography (NIL). NIL has emerged as a scalable manufacturing technology capable of producing features down to the hundred nanometer scale with the potential for large scale (roll-to-roll) manufacturing. In this paper, we present results on the modeling, fabrication and characterization of single mode waveguides and optical components in low-loss ORMOCER™ materials. Single mode waveguides with a mode field diameter of 7 μm and passive structures such as bends, directional couplers and multi-mode interferometers (MMIs) suitable for use in 1550 nm optical interconnects were fabricated using wafer scale NIL processes. Process issues arising from the nano-imprint technique such as residual layers and angled sidewalls are modeled and investigated for excess loss and higher order mode excitation. Conclusions are drawn on the applicability of nano-imprinting to the fabrication of circuits for intrachip/ board-level optical interconnect.