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Colossal Terahertz Nonlinearity in Angstrom- and Nanometer-Sized Gaps

Title
Colossal Terahertz Nonlinearity in Angstrom- and Nanometer-Sized Gaps
Author
전형탁
Keywords
terahertz nonlinearity; quantum tunneling; angstrom gap; metal−insulator−metal; graphene; aluminum oxide
Issue Date
2016-08
Publisher
AMER CHEMICAL SOC
Citation
ACS PHOTONICS, v. 3, NO. 8, Page. 1440-1445
Abstract
We investigated optical nonlinearity induced by electron tunneling through an insulating vertical gap between metals, both at terahertz frequency and at near-infrared frequency. We adopted graphene and alumina layers as gap materials to form gap widths of 3 angstrom and 1.5 nm, respectively. Transmission measurements show that tunneling-induced transmittance changes from strong fields at the gaps can be observed with relatively weak incident fields at terahertz frequency due to high field enhancement, whereas nonlinearity at the near-infrared frequency is restricted by laser-induced metal damages. Even when the same level of tunneling currents occurs at both frequencies, transmittance in the terahertz regime decreases much faster than that in the near-infrared regime. An equivalent circuit model regarding the tunneling as a resistance component reveals that strong terahertz nonlinearity is due to much smaller displacement currents relative to tunneling currents, also explaining small nonlinearity of the near-infrared regime with orders of magnitude larger displacement currents.
URI
https://pubs.acs.org/doi/10.1021/acsphotonics.6b00103http://repository.hanyang.ac.kr/handle/20.500.11754/76183
ISSN
2330-4022
DOI
10.1021/acsphotonics.6b00103
Appears in Collections:
COLLEGE OF ENGINEERING[S](공과대학) > MATERIALS SCIENCE AND ENGINEERING(신소재공학부) > Articles
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