Showing posts with label Xiaowei He. Show all posts
Showing posts with label Xiaowei He. Show all posts

Thursday, May 29, 2014

Abstract-Carbon Nanotube Terahertz Detector


Xiaowei He Naoki Fujimura Jennifer Meagan 
Nano Lett., Just Accepted Manuscript
DOI: 10.1021/nl5012678
Publication Date (Web): May 29, 2014
Copyright © 2014 American Chemical Society

Terahertz (THz) technologies are promising for diverse areas such as medicine, bioengineering, astronomy, environmental monitoring, and communications. However, despite decades of world-wide efforts, the THz region of the electromagnetic spectrum still continues to be elusive for solid state technology. Here, we report on the development of a powerless, compact, broadband, flexible, large-area, and polarization-sensitive CNT THz detector that works at room temperature. The detector is sensitive throughout the entire range of the THz technology gap, with responsivities as high as 2.5 V/W and polarization ratios as high as 5:1. Complete thermoelectric and opto-thermal characterization together unambiguously reveal the photothermoelectric origin of the THz photosignal, triggered by plasmonic absorption and collective antenna effects, and suggest that judicious design of thermal management and quantum engineering of Seebeck coefficients will lead to further enhancement of device performance.

Monday, February 3, 2014

Abstract-High-Contrast Terahertz Wave Modulation by Gated Graphene Enhanced by Extraordinary Transmission through Ring Apertures


Nano Lett., Just Accepted Manuscript
DOI: 10.1021/nl4041274
Publication Date (Web): February 3, 2014
Copyright © 2014 American Chemical Society


Gate-controllable transmission of terahertz (THz) radiation makes graphene a promising material for making high-speed THz wave modulators. However, to date, graphene-based THz modulators have exhibited only small on/off ratios due to small THz absorption in single-layer graphene. Here we demonstrate a ~50% amplitude modulation of THz waves with gated single-layer graphene by the use of extraordinary transmission through metallic ring apertures placed right above the graphene layer. The extraordinary transmission induced ~7 times near-filed enhancement of THz absorption in graphene. These results promise CMOS-compatible THz modulators with tailored operation frequencies, large on/off ratios, and high speeds, ideal for applications in THz communications, imaging, and sensing.