Abstract-Additive manufacturing of highly reconfigurable plasmonic circuits for terahertz communications

Yang Cao, Kathirvel Nallappan, Hichem Guerboukha, Guofu Xu, and Maksim Skorobogatiy

(a) Schematic of the two-wire WBG (top) and a photo from the top with half of the cage removed (bottom). (b) (I) Schematic of a single period of the WBG that comprises two sections, one containing a blank paper sheet, and the other containing metallized paper with the corresponding transverse cross-sections shown in (II) and (III). The electric field distributions (|𝐸|$|E|$) of principal modes propagating in Section 1–Mode 1 (IV), and Section 2–Mode 2 (V), and Mode 3 (VI) at 140 GHz. (c) Simulated modal electric field distribution (|𝐸|$|E|$) of a WBG in the symmetry plane in the mid gap between the two wires at 140 GHz. (d) Simulated power transmission |S21|2$|{\mathrm{S}21|}^2$ and reflection |S11|2$|{\mathrm{S}11|}^2$ coefficients for WBGs with different number of periods. (e) Experimentally measured transmittance of the paper/metal WBGs of different lengths inserted into a 10 cm-long two-wire waveguide. Transmittance is computed by dividing the grating transmission spectra (by field) by that of an empty two-wire waveguide (reference).

https://www.osapublishing.org/optica/abstract.cfm?uri=optica-7-9-1112

While in most existing terahertz communications systems, the THz carrier wave is transmitted via free-space channels, the THz waveguide-based integrated solutions can be of great utility at both the transmitter and receiver ends, thus simplifying the miniaturization and mass production of cost-effective THz communications systems. Here we present a new type of modular THz integrated circuits based on the two-wire plasmonic waveguide components fabricated using a combination of stereolithography (SLA) 3D printing, wet chemistry metal deposition, and hot stamping techniques. Particular attention is paid to the design of the optical circuits based on the two-wire waveguides suspended inside a protective micro-sized enclosure. Such waveguides feature low transmission and bending losses, as well as low dispersion. Using such waveguides as basic building blocks, we then demonstrate several key optical subcomponents, such as low-loss broadband 2×1THz$2\times 1\mathrm{T}\mathrm{H}\mathrm{z}$ couplers that use two coalescing two-wire waveguide bends, as well as broadband waveguide Bragg gratings that feature a paper sheet with a periodic sequence of metal strips inserted into the air gap of a two-wire waveguide. Finally, using these developed subcomponents, a two-channel add-drop multiplexer is demonstrated to operate at 140 GHz. We believe that the reported micro-encapsulated two-wire waveguide-based modular platform can have a strong impact on the field of THz signal processing and sensing due to the ease of device fabrication and handling, high degree of reconfigurability, and high potential for real-time tunability.

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