Abstract
Positively and negatively charged polyelectrolytes, namely, Poly(diallyldimethylammonium chloride) and Poly(styrene sulfonate), respectively, were employed to disperse and deploy negatively charged quantum dots on an otherwise passive metamaterial structure with a resonant frequency of 0.62 THz, by employing a layer-by-layer, self-assembly scheme. Upon exposure to a UV source with a wavelength of 365 nm the amplitude modulation was observed to increase with increases in the number of deposited bi-layers, until a modulation maximum of 2.68% was recorded enabling an all-optical, dynamically reconfigurable metamaterial geometry. Furthermore, amplitude modulation was subsequently observed to decrease with further increases in the number of layers employed due to quenching and shadowing effects. The experimental observations reported herein will enable the utilization of all-optical reconfigurable THz devices for communication and data transmission applications.
Highlights
The ability to control the amplitude, phase and/or polarization of electromagnetic waves remains of critical importance for all technological applications
This is applicable to Terahertz (THz) radiation, ranging from 100 GHz to 5 THz that is of interest to scientists and technologists because electromagnetic waves at those frequencies can excite intra- and intermolecular resonances due to mo
A variety of schemes have been suggested and explored to achieve reconfigurable metamaterial performance including the dynamic adjustment of the dimensions or the spacing of the structures which can be effected either by employing flexible surfaces [23] [24] or microactuating mechanisms frequently associated with MEMS technology [25] [26]
Summary
The ability to control the amplitude, phase and/or polarization of electromagnetic waves remains of critical importance for all technological applications. THz devices are, in general, faster and more sensitive, compared to their counterparts in other regions of the electromagnetic spectrum [17]; the paucity of naturally occurring materials with a suitable performance in the THz regime has made the advance of terahertz devices and applications rather arduous This shortcoming can be addressed by the judicious utilization of metamaterials, which are artificial media with subwavelength unit cells that can be designed to achieve arbitrary (negative or positive) permittivity and permeability values, and can be custom-tailored to exhibit resonances at a desired frequency even in the THz regime [18] [19] [20] [21] [22]. Their ability to modulate the response of a metamaterial array operating in the THz regime has not been demonstrated yet
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