A fabrication process for PFCB waveguide air-trench bends with scanning electron microscope (SEM)-based electron
beam lithography (EBL) and autoalignment has been developed and high efficiency air-trench bends (97.2% for TE
polarization and 96.2% for TM polarization) have been demonstrated. We have successfully developed a high aspect
ratio (18:1) anisotropic PFCB etch using a CO/O<sub>2</sub> etch chemistry in an inductively coupled plasma reactive ion etcher
(ICP RIE) for PFCB waveguide air-trench splitter fabrication. The fabricated splitters show a 90.1% overall efficiency
and ~ 85-to-15 (85:15) splitting ratio for 950 nm wide splitter trench, which closely matches 2D-FDTD simulation
results. Using air-trench bends, an ultracompact PFCB arrayed waveguide grating (AWG) 8 x 8 wavelength
demultiplexer for Wavelength Division Multiplexing (WDM) application had been designed. Compared to a
conventional AWG in the same material system, the air-trench bend AWG reduces the area required by a factor of 20.
Compact ring resonators using these splitters and bends has been designed and fabrication and improvements are
High efficiency small-area waveguide bends and splitters for perfluorocyclobutane (PFCB) copolymer materials have been designed with air trench structures (ATSs). An air trench at the intersection of one input and two output waveguides can function as a high efficiency splitter. High efficiency small-area waveguide bends are achieved by placing ATSs at the waveguide bend corners and operate through total internal reflection (TIR). In this paper we discuss bends and splitters that are designed specifically for constructing a ring resonator and a Mach-Zender interferometer. Two dimensional (2-D) finite difference time domain (FDTD) analysis has been used for design. In order to further examine the performance of realistic small-area air trench bend structures, we have also employed three dimensional (3-D) FDTD. From 3-D FDTD simulation results, we find that the 2-D designs are representative of actual devices. By combining small-area air trench bends and splitters, we show how a compact ring resonator can be realized. Simulation results show attractive properties for the proposed ring resonator design. Preliminary ATS etch results of PFCB with CO and O<sub>2</sub> shows the possibility of fabricating the proposed devices.