Abstract
We investigate in detail the crosstalk between plasmonic slot waveguides. We show that the coupling behavior of deep subwavelength three-dimensional (3-D) plasmonic slot waveguides is very different from the one of two-dimensional (2-D) metal-dielectric-metal (MDM) plasmonic waveguides. While in the 2-D case the coupling occurs only through the metal, in the 3-D case the coupling occurs primarily through the dielectric, in which the evanescent tail is much larger compared to the one in the metal. Thus, in most cases the coupling between 3-D plasmonic slot waveguides is much stronger than the coupling between the corresponding 2-D MDM plasmonic waveguides. Such strong coupling can be exploited to form directional couplers using plasmonic slot waveguides. On the other hand, with appropriate design, the crosstalk between 3-D plasmonic slot waveguides can be reduced even below the crosstalk levels of 2-D MDM plasmonic waveguides, without significantly affecting their modal size and attenuation length. Thus, 3-D plasmonic slot waveguides can be used for ultradense integration of optoelectronic components.
Highlights
The capability of guiding light at deep subwavelength scales is of great interest in optoelectronics, in part because such capability may enable ultradense integration of optoelectronic circuits
Two-conductor waveguide geometries, which are the optical analogue of microwave transmission lines, are of particular interest because they support modes at deep subwavelength scale with high group velocity over very wide range of frequencies
As a prominent example of two-conductor waveguide geometries, 3-D plasmonic slot waveguides, consisting of a deep subwavelength slot introduced in a thin metallic film, were recently investigated [1,2,3,4]
Summary
The capability of guiding light at deep subwavelength scales is of great interest in optoelectronics, in part because such capability may enable ultradense integration of optoelectronic circuits. This prospect for integration has motivated significant recent activities in exploring plasmonic waveguide structures. Two-conductor waveguide geometries, which are the optical analogue of microwave transmission lines, are of particular interest because they support modes at deep subwavelength scale with high group velocity over very wide range of frequencies. A key consideration is the packing density of optical waveguides and devices. The coupling strength between two waveguides sets a limit on their maximum packing density
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