We propose an integrated waveguide depolarizer for use in interferometric fiber optic gyroscopes (IFOGs) with single-mode fiber coils. The integrated waveguide depolarizer is based on a Mach-Zender interferometer with polarizing beamsplitters. A waveguide polarizing beamsplitter is designed using multiple air trench structures oriented at the Brewster angle. We also analyze the effect of component imperfections on the degree of polarization achievable with an integrated waveguide depolarizer.
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 O2 shows the possibility of fabricating the proposed devices.
Dramatic reductions in the size of waveguide bends for materials with low core/clad refractive index contrast can be achieved with single air interface bends (SAIBs) based on total internal reflection. However, high optical efficiency for such bends requires vertical interfaces with low surface roughness. In this presentation we report the development of a highly anisotropic etch for perfluorocyclobutane (PFCB) waveguide structures. We examine the use of inductively coupled plasma reactive ion etching (ICP RIE) based on both oxygen/helium and carbon dioxide/helium etch chemistries to achieve the desired interface quality for high efficiency waveguide bends.