Are negative index materials achievable with surface plasmon waveguides? A case study of three plasmonic geometries.
We present a theoretical analysis of planar plasmonic waveguides that support propagation of positive and negative index modes. Particular attention is given to the modes sustained by metal-insulator-metal (MIM), insulator-metal-insulator (IMI), and insulator-insulator-metal (IIM) geometries at visible and near-infrared frequencies. We find that all three plasmonic structures are characterized by negative indices over a finite range of visible frequencies, with figures of merit approaching 20. Moreover, using finite-difference time-domain simulations, we demonstrate that visible-wavelength light propagating from free space into these waveguides can exhibit negative refraction. Refractive index and figure-of-merit calculations are presented for Ag/GaP and Ag/Si(3)N(4) - based structures with waveguide core dimensions ranging from 5 to 50 nm and excitation wavelengths ranging from 350 nm to 850 nm. Our results provide the design criteria for realization of broadband, visible-frequency negative index materials and transformation-based optical elements for two-dimensional guided waves. These geometries can serve as basic elements of three-dimensional negative-index metamaterials.
Dionne
Jennifer A
JA
Thomas J. Watson Laboratories of Applied Physics, California Institute of Technology, Pasadena, CA 91125, USA. jdionne@caltech.edu
Verhagen
Ewold
E
Polman
Albert
A
Atwater
Harry A
HA
D003198:Computer Simulation; D017076:Computer-Aided Design; D004867:Equipment Design; D019544:Equipment Failure Analysis; D008420:Manufactured Materials; D008962:Models, Theoretical; D012031:Refractometry / Q000295:instrumentation* / Q000379:methods*; D020349:Surface Plasmon Resonance / Q000295:instrumentation* / Q000379:methods*