Abstract
We demonstrate propagation of terahertz waves confined to a semiconductor surface that is periodically corrugated with V-shaped grooves. A one-dimensional array of V-grooves is fabricated on a highly-doped silicon surface, using anisotropic wet-etching of crystalline silicon, thereby forming a plasmonic waveguide. Terahertz time domain spectroscopy is used to characterize the propagation of waves near the corrugated surface. We observe that the grating structure creates resonant modes that are confined near the surface. The degree of confinement and frequency of the resonant mode is found to be related to the pitch and depth of the V-grooves. The surface modes are confirmed through both numerical simulations and experimental measurements. Not only does the V-groove geometry represent a new and largely unexplored structure for supporting surface waves, but it also enables the practical fabrication of terahertz waveguides directly on semiconductor surfaces, without relying on reactive-ion etching or electroplating of sub-millimeter metallic surfaces.
Highlights
In recent years, electromagnetic waves propagating at the interface between a metal and dielectric have been of significant interest [1,2,3,4,5,6,7]
In 2004, Pendry et al proposed the introduction of a periodic texture to a conducting surface in order to compensate for the wavevector mismatch, allowing for excitation of surface waves with a wavenumber that exceeds that of the excitation [12]
The terahertz wave at the resonance associated with the null get strongly trapped to the grating leading to the strong confinement
Summary
Electromagnetic waves propagating at the interface between a metal and dielectric have been of significant interest [1,2,3,4,5,6,7]. At visible and near infrared frequencies, many conventional metal surfaces support localized surface plasmon polariton modes that can be excited using prism-coupling methods [11]. Modes have been demonstrated in several geometries, including metallic apertures, blind holes, rectangular gratings, and others Most of these devices have used laser micromachining, or planar photolithographic techniques such as liftoff, reactive-ion etching, thin-film deposition, and electroplating to form rectangular conductive features on a substrate. Wood et al numerically analyzed a surface plasmon mode sustained by periodic array of slanted rectangular grooves in a conductive substrate [28]. Silicon can exhibit metallic properties when heavily doped and can be used to efficiently propagate spoof plasmon polaritons when patterned with subwavelength structures. We report terahertz spoof plasmon polariton propagation on a highly doped silicon surface that is patterned with periodic V-grooves.
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