Abstract-Conductivity mapping of graphene on polymeric films by terahertz time-domain spectroscopy

Patrick R. Whelan, Deping Huang, David Mackenzie, Sara A. Messina, Zhancheng Li, Xin Li, Yunqing Li, Timothy J. Booth, Peter U. Jepsen, Haofei Shi, Peter Bøggild,

https://www.osapublishing.org/oe/fulltext.cfm?uri=oe-26-14-17748

Fast inline characterization of the electrical properties of graphene on polymeric substrates is an essential requirement for quality control in industrial graphene production. Here we show that it is possible to measure the sheet conductivity of graphene on polymer films by terahertz time-domain spectroscopy (THz-TDS) when all internally reflected echoes in the substrate are taken into consideration. The conductivity measured by THz-TDS is comparable to values obtained from four point probe measurements. THz-TDS maps of 25x30 cm2 area graphene films were recorded and the DC conductivity and carrier scattering time were extracted from the measurements. Additionally, the THz-TDS conductivity maps highlight tears and holes in the graphene film, which are not easily visible by optical inspection.

© 2018 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

Abstract-Single-layer plasmonic metasurface half-wave plates with wavelength-independent polarization conversion angle

Zhaocheng Liu, Zhancheng Li, Zhe Liu, Hua Cheng, Wenwei Liu, Chengchun Tang, Changzhi Gu, Junjie Li, Hou-Tong Chen, Shuqi Chen, and Jianguo Tian

ACS Photonics, Just Accepted Manuscript

DOI: 10.1021/acsphotonics.7b00491

Publication Date (Web): June 30, 2017

Copyright © 2017 American Chemical Society

http://pubs.acs.org/doi/abs/10.1021/acsphotonics.7b00491?journalCode=apchd5

Manipulation of polarization state is of great fundamental importance and plays a crucial role in modern photonic applications such as optical communication, imaging and sensing. Metamaterials and metasurfaces have attracted increasing interest in this area because they facilitate designer optical response through engineering the composite subwavelength structures. Here we propose a general methods of designing half-wave plate, and demonstrate in the near-infrared wavelength range an optically thin plasmonic metasurface half-wave plates that rotate the polarization direction of the linearly polarized incident light with a high degree of linear polarization. The half-wave plate functionality is realized through arranging the orientation of the nanoantennas to form an appropriate spatial distribution profile, which behave exactly as in classical half-wave plates but over in a wavelength-independent way.

Abstract- Realization of broadband cross-polarization conversion in transmission mode in the terahertz region using a single-layer metasurface

Wenwei Liu, Shuqi Chen, Zhancheng Li, Hua Cheng, Ping Yu, Jianxiong Li, and Jianguo Tian

https://www.osapublishing.org/ol/abstract.cfm?URI=ol-40-13-3185#Abstract

We present the design specifications and in-depth analysis of a terahertz (THz) broadband cross-polarization converter composed of a single-layer metasurface. This device can convert linearly polarized light into its cross-polarization in transmission mode. Different from other polarization conversion devices, this effect results from the suppression and enhancement for different electric components. The broadband characteristic is also achieved by specific partial symmetries designed in the structure. The proposed polarization converter can aid in the development of novel plasmonic polarization devices, and can help to overcome certain limitations of the customary designs that have been proposed thus far.

© 2015 Optical Society of America

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