Modal analysis and coupling in metal-insulator-metal waveguides

作     者：Şükrü Ekin Kocabaş Georgios Veronis David A. B. Miller Shanhui Fan 

作者机构：Ginzton Laboratory Stanford University Stanford California 94305 USA Department of Electrical and Computer Engineering and Center for Computation and Technology Louisiana State University Baton Rouge Louisiana 70803 USA 

出 版 物：《Physical Review B》 (Phys. Rev. B Condens. Matter Mater. Phys.)

年 卷 期：2009年第79卷第3期

页      面：035120-035120页

核心收录：

学科分类：0808[工学-电气工程] 0809[工学-电子科学与技术（可授工学、理学学位）] 07[理学] 0805[工学-材料科学与工程（可授工学、理学学位）] 0702[理学-物理学] 

基　　金：DARPA MTO Interconnect Focus Center Focus Center Research Program DARPA Semiconductor Research Corporation program USAFOSR "Plasmon Enabled Nanophotonic Circuits" MURI Program 

主　　题：finite difference methods frequency-domain analysis MIM devices modal analysis optical waveguides plasmons Sturm-Liouville equation 

摘      要：This paper shows how to analyze plasmonic metal-insulator-metal waveguides using the full modal structure of these guides. The analysis applies to all frequencies, particularly including the near infrared and visible spectrum, and to a wide range of sizes, including nanometallic structures. We use the approach here specifically to analyze waveguide junctions. We show that the full modal structure of the metal-insulator-metal (MIM) waveguides—which consists of real and complex discrete eigenvalue spectra, as well as the continuous spectrum—forms a complete basis set. We provide the derivation of these modes using the techniques developed for Sturm-Liouville and generalized eigenvalue equations. We demonstrate the need to include all parts of the spectrum to have a complete set of basis vectors to describe scattering within MIM waveguides with the mode-matching technique. We numerically compare the mode-matching formulation with finite-difference frequency-domain analysis and find very good agreement between the two for modal scattering at symmetric MIM waveguide junctions. We touch upon the similarities between the underlying mathematical structure of the MIM waveguide and the PT symmetric quantum-mechanical pseudo-Hermitian Hamiltonians. The rich set of modes that the MIM waveguide supports forms a canonical example against which other more complicated geometries can be compared. Our work here encompasses the microwave results but extends also to waveguides with real metals even at infrared and optical frequencies.