Metamaterials at terahertz frequencies offer unique opportunities, but are challenging to fabricate in bulk. We adapt the fabrication procedure for microstructured polymer optical fibers to inexpensively fabricate metamaterials potentially on an industrial scale. We produce polymethylmethacrylate fibers containing ~10 μm diameter indium wires separated by ~100 μm, which exhibit a terahertz plasmonic response.
Metamaterials are man-made composite materials, fabricated by assembling components much smaller than the wavelength at which they operate 1. They owe their electromagnetic properties to the structure of their constituents, instead of the atoms that compose them. For example, sub-wavelength metal wires can be arranged to possess an effective electric permittivity that is either positive or negative at a given frequency, in contrast to the metals themselves 2. This unprecedented control over the behaviour of light can potentially lead to a number of novel devices, such as invisibility cloaks 3, negative refractive index materials 4, and lenses that resolve objects below the diffraction limit 5. However, metamaterials operating at optical, mid-infrared and terahertz frequencies are conventionally made using nano- and micro-fabrication techniques that are expensive and produce samples that are at most a few centimetres in size 6-7. Here we present a fabrication method to produce hundreds of meters of metal wire metamaterials in fiber form, which exhibit a terahertz plasmonic response 8. We combine the stack-and-draw technique used to produce microstructured polymer optical fiber 9 with the Taylor-wire process 10, using indium wires inside polymethylmethacrylate (PMMA) tubes. PMMA is chosen because it is an easy to handle, drawable dielectric with suitable optical properties in the terahertz region; indium because it has a melting temperature of 156.6 °C which is appropriate for codrawing with PMMA. We include an indium wire of 1 mm diameter and 99.99% purity in a PMMA tube with 1 mm inner diameter (ID) and 12 mm outside diameter (OD) which is sealed at one end. The tube is evacuated and drawn down to an outer diameter of 1.2 mm. The resulting fiber is then cut into smaller pieces, and stacked into a larger PMMA tube. This stack is sealed at one end and fed into a furnace while being rapidly drawn, reducing the diameter of the structure by a factor of 10, and increasing the length by a factor of 100. Such fibers possess features on the micro- and nano- scale, are inherently flexible, mass-producible, and can be woven to exhibit electromagnetic properties that are not found in nature. They represent a promising platform for a number of novel devices from terahertz to optical frequencies, such as invisible fibers, woven negative refractive index cloths, and super-resolving lenses.
The technique presented here allows the fabrication of kilometers of continuous three-dimensional metamaterials with microscale feature sizes, possessing a plasmonic response (and thus a tailored electric permittivity) in the THz range, effectively behaving as a high-pass filter. This can be experimentally characterized using terahertz time-domain spectroscopy 11. Such fiber-shaped metamaterials can be cut and stacked into bulk materials to realize a large number of devices, or woven into other structures, for…
The authors have nothing to disclose.
This research was supported under Australian Research Council’s Discovery Projects funding scheme (project number DP120103942). B. T. K. and A. A. are the recipients of an Australian Research Council Future Fellowship (FT0991895) and Australian Research Fellowship (DP1093789) respectively.
Name of Reagent/Material | Company | Catalogue Number | Comments |
Indium 99.99% Wire, 1 mm diameter | AIM Specialty | Available on request | www.aimspecialty.com http://www.aimspecialty.com/Portals/0/Files/Indium.pdf |
2-Propanol(Isopropanol) | Sigma-Aldrich | Product Number 190764 |
http://www.sigmaaldrich.com/chemistry/solvents/products.html?TablePage=17292086 |
Adhesive tape | Staples | ||
One Wrap PTFE Tape, 5 ml x 12 mmW x 0.2 mmT | RS Components | RS Stock Number 231-964 |
http://uk.rs-online.com/web/p/ptfe-tapes/0231964/ |
50 Micron Aluminium Foil Tape | Advance Adhesive Tapes | AT506 | http://www.advancetapes.com/Products/types/9/page1/81 |
Blu-tak | Bostik | http://www.blutack.com/index.html | |
Araldite Quick Set | Selleys | http://selleys.com.au/adhesives/household-adhesive/araldite/quick-set | |
PMMA tubes: – ID 6 mm, OD 12 mm – ID 9 mm, OD 12 mm |
B & M Plastics: Plastic Fabrication | Available on request | http://www.bmplastics.com.au/about-us.htm |
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