Fabrication of compact polymer waveguide devices using air-trench bends and splitters

A fabrication process for PFCB waveguide air-trench bends and splitters with scanning electron microscope (SEM)-based electron beam lithography (EBL) with alignment accuracy better than 40 nm has been developed. High efficiency air-trench bends (97.2% for TE polarization and 96.2% for TM polarization) have been demonstrated. The fabrication of air-trench splitters is challenging because of the small trench width (800 nm) and deep and anisotropic trench etch (14.5 mum). We have successfully developed a high aspect ratio (18:1) anisotropic PFCB etch using a CO/O₂ etch chemistry in an inductively coupled plasma reactive ion etcher (ICP RIE) for PFCB waveguide air-trench splitter fabrication. Using air-trench bends, an ultracompact PFCB arrayed waveguide grating (A WG) 8 x 8 wavelength demultiplexer for Wavelength Division Multiplexing (WDM) application had been designed and fabricated. Compared to a conventional AWG in the same material system, the air- trench bend A WG reduces the area required by a factor of 20.