Efficient modeling of optical waveguides and fibers with chemical sensing applications

The impedance boundary method of moments (IBMOM) for planar optical waveguides is reviewed. An extension of the IBMOM for optical fibers with truncated graded index profile is described. Results for a step index fiber show that virtually exact solutions for the modal field profile and propagation constant can be obtained with only three Legendre expansion functions. The IBMOM is applied in the design and analysis of an evanescent field optical waveguide chemical sensor which utilizes an antiresonant reflecting optical waveguide (ARROW) structure and is implemented as a Mach-Zehnder interferometer. The ARROW structure allows the use of a 5 micrometer wide guiding region for efficient coupling into a single mode optical fiber. The ARROW sensor is designed for a sensitivity of 180 degrees/cm phase change for a change of 0.05 in refractive index.