We analyze a dielectric waveguide with a photonic crystal core. Using constant frequency contour analysis, we show that the modal behavior of this structure is drastically different from that of a conventional slab waveguide. In particular, at a given frequency the lowest-order guided mode can have an odd symmetry or can have more than one nodal plane in its field distribution. Also, there exist several single-mode regions with a different modal profile in each region. Finally, a single-mode waveguide for the fundamental mode with a large core and strong confinement can be realized. All these behaviors are confirmed by our three-dimensional finite-difference time-domain simulations.
© 2006 Optical Society of America
Original Manuscript: August 31, 2005
Revised Manuscript: November 11, 2005
Manuscript Accepted: November 17, 2005
Xiaofang Yu, Wah Tung Lau, and Shanhui Fan, "Anomalous modal structure in a waveguide with a photonic crystal core," Opt. Lett. 31, 742-744 (2006)