<title>Design of rectangular waveguides for integrated optics with mode matching techniques</title>

Abstract

Rectangular core waveguides for integrated optics have been designed by the mode matching (transverse resonance) method. To achieve good coupling between the waveguides and an optical fiber, the core cross section of the waveguide at the fiber/waveguide interface has been optimized with regard to minimum coupling loss. In calculating the overlap integral between the fundamental mode of the waveguide and the fiber a very accurate fiber model has been used. Calculations of the effective index and the field distribution of the fundamental fiber mode with this model have been compared with analytic results for circular step-index-fibers. The convergence behavior and accuracy of overlap integral calculations with the mode matching method has been investigated. The calculations show that losses as low as 0.16 dB can be reached for waveguides with refractive index contrasts in the whole range 0.5 to 2%.