The contradirectional coupling between a pair of planar dielectric waveguides, whose guiding layers are respectively a negative index medium and a positive index medium (PIM, i.e., the conventional medium), is theoretically investigated using the coupled mode theory. It is shown that, by tapering the middle segment of the PIM guiding layer to introduce a certain phase shift, the energy flow circulation can be established based on the contradirectional coupling effect, and, thus, the electromagnetic energy is localized in the waveguide system. This phenomenon is further verified numerically with the finite-difference time domain method. The quality factor of this open waveguide cavity is also discussed.
© 2011 Optical Society of America
Original Manuscript: October 4, 2010
Revised Manuscript: December 15, 2010
Manuscript Accepted: December 29, 2010
Published: March 18, 2011
Tao Jiang, Linfang Shen, and Lixin Ran, "Localization of electromagnetic energy by a pair of parallel waveguides with contradirectional coupling," J. Opt. Soc. Am. B 28, 760-764 (2011)