Plasmon-induced transparency in subwavelength metal-dielectric-metal waveguides

Document Type

Conference Proceeding

Publication Date

4-11-2011

Abstract

Plasmonic devices, based on surface plasmons propagating at metal-dielectric interfaces, have shown the potential to guide and manipulate light at deep subwavelength scales. In addition, slowing down light in plasmonic waveguides leads to enhanced light-matter interaction, and could therefore enhance the performance of nanoscale plasmonic devices such as switches and sensors. In this paper, we introduce slow-light subwavelength plasmonic waveguides based on a plasmonic analogue of electromagnetically induced transparency (EIT). Both the operating wavelength range and the slowdown factor of the waveguides are tunable. The structure consists of a periodic array of two metal-dielectric-metal (MDM) stub resonators side-coupled to a MDM waveguide. The two cavities in each unit cell have a resonant frequency separation which can be tuned by adjusting the cavity dimensions. We show that in the vicinity of the two cavity resonant frequencies, the system supports three photonic bands, and the band diagram is similar to that of EIT systems. The middle band corresponds to a mode with slow group velocity and zero group velocity dispersion in the middle of the band. Decreasing the resonant frequency separation, increases the slowdown factor, and decreases the bandwidth of the middle band. We also find that metal losses lead to a tradeoff between the slowdown factor and the propagation length of the supported optical mode. We use a single-mode scattering matrix theory to account for the behavior of the waveguides, and show that it is in excellent agreement with numerical results obtained with the finite-difference frequency-domain method.

Publication Source (Journal or Book title)

Proceedings of SPIE - The International Society for Optical Engineering

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