Geometries and materials for subwavelength surface plasmon modes

• Published in: Journal of the Optical Society of America. A, Optics, image science, and vision Vol. 21; no. 12; p. 2442
• Main Authors: Zia, Rashid, Selker, Mark D, Catrysse, Peter B, Brongersma, Mark L
• Format: Journal Article
• Language: English
• Published: United States 01.12.2004
• Subjects: Computer Simulation; Computer-Aided Design; Electric Impedance; Equipment Design - methods; Equipment Failure Analysis - methods; Metals - chemistry; Surface Plasmon Resonance - instrumentation; Surface Plasmon Resonance - methods
• ISSN: 1084-7529
• DOI: 10.1364/josaa.21.002442

Plasmonic waveguides can guide light along metal-dielectric interfaces with propagating wave vectors of greater magnitude than are available in free space and hence with propagating wavelengths shorter than those in vacuum. This is a necessary, rather than sufficient, condition for subwavelength confinement of the optical mode. By use of the reflection pole method, the two-dimensional modal solutions for single planar waveguides as well as adjacent waveguide systems are solved. We demonstrate that, to achieve subwavelength pitches, a metal-insulator-metal geometry is required with higher confinement factors and smaller spatial extent than conventional insulator-metal-insulator structures. The resulting trade-off between propagation and confinement for surface plasmons is discussed, and optimization by materials selection is described.