title: Slow-light-enhanced codirectional couplers with negative index materials.
abstract: Optical codirectional coupling structures consisting of two parallel planar waveguides with negative index materials (NIMs) are systematically studied in different configurations using coupled-mode theory under the weak-coupling condition. As a result, we find that the coupling strength between copropagating optical modes can be enhanced in such structures. More importantly, both our analytical derivations and numerical simulations clearly indicate that the slow-light effect in the waveguides with NIMs plays an essential role in such enhancement. The configuration with two conventional positive-index-material cores embedded in NIM claddings (or vice versa) can lead to the strongest enhancement because it can give rise to the slowest light in our scheme. Therefore, as well as offering a fundamental understanding of the slow-light effect in codirectional coupling structures with NIMs for constructing compact photonic devices, our investigations suggest a useful guideline for optimizing the design of codirectional couplers using slow-light systems for both the classical and quantum information processing and communication networks.
authors.affiliation: Department of Physics, Tsinghua University, Beijing 100084, China. zhaol@phys.tsinghua.edu.cn
authors.forename: L
authors.initials: L
authors.lastname: Zhao
authors.forename: Wenhui
authors.initials: W
authors.lastname: Duan