Fabrication and replication of polymer integrated optical devices using electron-beam lithography and soft lithography

Polymeric integrated optical devices, including microring resonator optical filters and Mach-Zehnder interferometer modulators, fabricated by electron-beam lithography and soft lithography are considered in this article. Microring resonator optical filters made of SU-8 (MicroChem, Newton, MA), directly patterned by electron-beam lithography, demonstrate that SU-8 is a good candidate for high-precision, easily fabricated, and good-optical-quality passive integrated optical devices. Due to the electron-beam lithography process, the coupling between the straight waveguide and the microring resonator is precisely controlled, and the critical coupling condition can be achieved. Additionally, films containing several devices patterned by electron-beam lithography are peeled from the silicon substrate, yielding ultrathin all-polymer flexible free-standing microring resonator optical filters exhibiting up to -27 dB filtering extinction. Using a PDMS stamp, molded from these electron-beam-patterned microring resonator optical filters, identical replicas are fabricated by the soft lithography molding technique. Soft lithography is also applied to active polymer materials. A short 2-mm active-section prototype Mach-Zehnder interferometer modulator is made by the replica molding process, using CLD-1/APC electrooptic polymer as the core material. A reasonable intensity-modulation effect is observed by applying voltage to one arm of the interferorneter.