This paper presents two-dimensional (2-D) finite difference time domain (FDTD) simulations of low-loss right-angle waveguide bends, T-junctions and crossings, based on high index-contrast waveguides. Such structures are essential for the dense integration of optical components. Excellent performance characteristics are obtained by designing the waveguide intersection regions as low-Q resonant cavities with certain symmetries and small radiation loss. A simple analysis, based on coupled mode theory in time, is used to explain the operation principles and agrees qualitatively with the numerical results.
C. Manolatou, Steven G. Johnson, Shanhui Fan, Pierre R. Villeneuve, H. A. Haus, and J. D. Joannopoulos, "High-Density Integrated Optics," J. Lightwave Technol. 17, 1682- (1999)