skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Anti-reflection coating design for metallic terahertz meta-materials

; ; ; ; ; ; ORCiD logo
Publication Date:
Sponsoring Org.:
OSTI Identifier:
Grant/Contract Number:
Resource Type:
Journal Article: Published Article
Journal Name:
Optics Express
Additional Journal Information:
Journal Volume: 26; Journal Issue: 3; Related Information: CHORUS Timestamp: 2018-01-26 09:39:48; Journal ID: ISSN 1094-4087
Optical Society of America
Country of Publication:
United States

Citation Formats

Pancaldi, Matteo, Freeman, Ryan, Hudl, Matthias, Hoffmann, Matthias C., Urazhdin, Sergei, Vavassori, Paolo, and Bonetti, Stefano. Anti-reflection coating design for metallic terahertz meta-materials. United States: N. p., 2018. Web. doi:10.1364/OE.26.002917.
Pancaldi, Matteo, Freeman, Ryan, Hudl, Matthias, Hoffmann, Matthias C., Urazhdin, Sergei, Vavassori, Paolo, & Bonetti, Stefano. Anti-reflection coating design for metallic terahertz meta-materials. United States. doi:10.1364/OE.26.002917.
Pancaldi, Matteo, Freeman, Ryan, Hudl, Matthias, Hoffmann, Matthias C., Urazhdin, Sergei, Vavassori, Paolo, and Bonetti, Stefano. 2018. "Anti-reflection coating design for metallic terahertz meta-materials". United States. doi:10.1364/OE.26.002917.
title = {Anti-reflection coating design for metallic terahertz meta-materials},
author = {Pancaldi, Matteo and Freeman, Ryan and Hudl, Matthias and Hoffmann, Matthias C. and Urazhdin, Sergei and Vavassori, Paolo and Bonetti, Stefano},
abstractNote = {},
doi = {10.1364/OE.26.002917},
journal = {Optics Express},
number = 3,
volume = 26,
place = {United States},
year = 2018,
month = 1

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record at 10.1364/OE.26.002917

Save / Share:
  • We demonstrate a silicon-based, single-layer anti-reflection coating that suppresses the reflectivity of metals at near-infrared frequencies, enabling optical probing of nano-scale structures embedded in highly reflective surroundings. Our design does not affect the interaction of terahertz radiation with metallic structures that can be used to achieve terahertz near-field enhancement. We have verified the functionality of the design by calculating and measuring the reflectivity of both infrared and terahertz radiation from a silicon/gold double layer as a function of the silicon thickness. We have also fabricated the unit cell of a terahertz meta-material, a dipole antenna comprising two 20-nm thick extendedmore » gold plates separated by a 2 μm gap, where the terahertz field is locally enhanced. We used the time-domain finite element method to demonstrate that such near-field enhancement is preserved in the presence of the anti-reflection coating. Finally, we performed magneto-optical Kerr effect measurements on a single 3-nm thick, 1-μm wide magnetic wire placed in the gap of such a dipole antenna. The wire only occupies 2% of the area probed by the laser beam, but its magneto-optical response can be clearly detected. Our design paves the way for ultrafast time-resolved studies, using table-top femtosecond near-infrared lasers, of dynamics in nano-structures driven by strong terahertz radiation.« less
  • Metamaterials/metasurfaces have enabled unprecedented manipulation of electromagnetic waves. Here we present a new design of metasurface structure functioning as antireflection coatings. The structure consists of a subwavelength metallic mesh capped with a thin dielectric layer on top of a substrate. By tailoring the geometric parameters of the metallic mesh and the refractive index and thickness of the capping dielectric film, reflection from the substrate can be completely eliminated at a specific frequency. Compared to traditional methods such as coatings with single- or multi-layer dielectric films, the metasurface antireflection coatings are much thinner and the requirement of index matching is largelymore » lifted. Here, this approach is particularly suitable for antireflection coatings in the technically challenging terahertz frequency range and is also applicable in other frequency regimes.« less
  • A very useful anti-reflection (AR) coating, having characteristics quite similar to silicon monoxide, has been grown on P/sup +/N solar cells by a simple technique. ESCA, infrared absorption, and ellipsometry analysis of the films indicated that they consist of silicon oxide with some bound hydrogen. Some added advantages of the new AR coating are described. 12 refs.
  • Transparent ZnO thin-films are prepared using the RF magnetron sputtering and spray pyrolysis techniques on the glass substrates. Reflectance spectra and thin films heights are measured using spectrophotometer and stylus surface profiler, respectively. Measured optical data is used for investigating the effect of the ZnO prepared by above two processes on the performance of Cu{sub 2}ZnSnS{sub 4} (CZTS) thin films solar cell (TFSC). One dimensional simulation approach is considered using the simulation program, SCAPS. External quantum efficiency and J-V characteristics of CZTS TFSC is simulated on the basis of optical reflectance data of ZnO films with and without ZnO thin-filmsmore » as antireflection coating (ARC). Study shows that ARC coated CZTS TFSC provides a better fill factor (FF) as compared to other ARC material such as MgF{sub 2}. Sprayed ZnO thin-films as ARC show comparable performance with the sputtered samples.« less
  • Interference lithography has proven to be a useful technique for generating periodic sub-diffraction limited nanostructures. Interference lithography can be implemented by exposing a photoresist polymer to laser light using a two-beam arrangement or more simply a one beam configuration based on a Lloyd's Mirror Interferometer. For typical photoresist layers, an anti-reflection coating must be deposited on the substrate to prevent adverse reflections from cancelling the holographic pattern of the interfering beams. For silicon substrates, such coatings are typically multilayered and complex in composition. By thinning the photoresist layer to a thickness well below the quarter wavelength of the exposing beam,more » we demonstrate that interference gratings can be generated without an anti-reflection coating on the substrate. We used ammonium dichromate doped polyvinyl alcohol as the positive photoresist because it provides excellent pinhole free layers down to thicknesses of 40 nm, and can be cross-linked by a low-cost single mode 457 nm laser, and can be etched in water. Gratings with a period of 320 nm and depth of 4 nm were realized, as well as a variety of morphologies depending on the photoresist thickness. This simplified interference lithography technique promises to be useful for generating periodic nanostructures with high fidelity and minimal substrate treatments.« less