Abstract-High extinction ratio terahertz wire-grid polarizers with connecting bridges on quartz substrates

John S. Cetnar, Shivashankar Vangala, Weidong Zhang, Carl Pfeiffer, Elliott R. Brown, and Junpeng Guo

https://www.osapublishing.org/ol/abstract.cfm?uri=ol-42-5-955&origin=search

A terahertz (THz) wire-grid polarizer with metallic bridges on a quartz substrate was simulated, fabricated, and tested. The device functions as a wide-band polarizer to incident THz radiation. In addition, the metallic bridges permit the device to function as a transparent electrode when a DC bias is applied to it. Three design variations of the polarizer with bridges and a polarizer without bridges were studied. Results show the devices with bridges have average 𝑠$s$-polarization transmittance of less than −3  dB$-3\mathrm{dB}$ and average extinction ratios of approximately 40 dB across a frequency range of 220–990 GHz and thus are comparable to a polarizer without bridges.

Abstract-High extinction ratio terahertz wire-grid polarizers with connecting bridges on quartz substrates

John S. Cetnar, Shivashankar Vangala, Weidong Zhang, Carl Pfeiffer, Elliott R. Brown, and Junpeng Guo

https://www.osapublishing.org/ol/abstract.cfm?uri=ol-42-5-955

A terahertz (THz) wire-grid polarizer with metallic bridges on a quartz substrate was simulated, fabricated, and tested. The device functions as a wide-band polarizer to incident THz radiation. In addition, the metallic bridges permit the device to function as a transparent electrode when a DC bias is applied to it. Three design variations of the polarizer with bridges and a polarizer without bridges were studied. Results show the devices with bridges have average 𝑠$s$-polarization transmittance of less than −3  dB$-3\mathrm{dB}$ and average extinction ratios of approximately 40 dB across a frequency range of 220–990 GHz and thus are comparable to a polarizer without bridges.

Abstract-Terahertz Transparent Electrode Using Tripod Metal Aperture Array

Abubaker M. Tareki,  Robert G. Lindquist,  Wonkyu Kim, Martin S. Heimbeck, Junpeng Guo

http://ieeexplore.ieee.org/document/7752979/

In this paper, a high transmission terahertz (THz), polarization insensitive electrode was designed and fabricated to modulate a liquid crystal electro-optic device in the THz regime. The designed electrode consists of a subwavelength periodic tripod aperture array structure patterned in a gold film deposited on a transparent dielectric substrate. The maximum feature size of the structure is maintained below a fraction of the thickness of the electro-optic device to allow a fringing field to uniformly excite the entire electrode area. The transmission reaches as high as 93% in measurements

Abstract-Terahertz metal grid polarizer with bridges on quartz substrate

John S. Cetnar

Air Force Research Lab. (United States)

Junpeng Guo

The Univ. of Alabama in Huntsville (United States)

Elliott R. Brown

Wright State Univ. (United States)

Proc. SPIE 9547, Plasmonics: Metallic Nanostructures and Their Optical Properties XIII, 95471O (August 28, 2015); doi:10.1117/12.2185114

http://proceedings.spiedigitallibrary.org/proceeding.aspx?articleid=2432846

The metal wire-grid polarizer is a venerable device that is used on radiation throughout the electromagnetic spectrum. It usually consists of a 1D-periodic array of subwavelength metallic wires in free space or mounted on a low-loss dielectric substrate, the plane of the grid being oriented perpendicular to the propagation direction. Herein is presented a new structure, a subwavelength wire-grid polarizer for the terahertz region that acts not only as a wideband polarizer but also as a transparent electrode. This function is achieved by the addition of periodically placed metallic bridges that connect the parallel metal wires of the polarizer. The bridges allow for the uniform distribution of an electrostatic potential over all wires while maintaining the polarizing functionality of the metal wire grid polarizer.

Full-wave electromagnetic simulations were performed on the device. The transmittance was computed in both perpendicular polarization and parallel polarization from 100 to 4000 GHz, and the extinction ratio was calculated across the same range. Furthermore, fill-factor studies were performed to understand how device performance is affected by varying slot width and bridge length, as well as bridge offset. The simulation results showed extraordinary optical transmission through the device for perpendicular polarization, creating excellent transmittance and extinction ratios over the frequency range. The perpendicular polarization transmittance and extinction ratio at 1 THz was calculated to be -1 dB and -36 dB respectively. Meanwhile, the bridges allow the device to behave like a DC electrode.
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