Abstract-Terahertz radiation-induced sub-cycle field electron emission across a split-gap dipole antenna

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Jingdi Zhang^1,2,a), Xiaoguang Zhao^3,a), Kebin Fan³, Xiaoning Wang³,Gu-Feng Zhang¹, Kun Geng², Xin Zhang^3,b) and Richard D. Averitt^1,2,b)
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1 Department of Physics, University of California, San Diego, La Jolla, California 92093, USA
2 Department of Physics, Boston University, Boston, Massachusetts 02215, USA
3 Department of Mechanical Engineering, Boston University, Boston, Massachusetts 02215, USA
a) J. Zhang and X. Zhao contributed equally to this work.
b) Authors to whom correspondence should be addressed. Electronic addresses:xinz@bu.edu and raveritt@ucsd.edu
Appl. Phys. Lett. 107, 231101 (2015); http://dx.doi.org/10.1063/1.4936841
http://scitation.aip.org/content/aip/journal/apl/107/23/10.1063/1.4936841


We use intense terahertz pulses to excite the resonant mode (0.6 THz) of a micro-fabricated dipole antenna with a vacuum gap. The dipole antenna structure enhances the peak amplitude of the in-gap THz electric field by a factor of ∼170. Above an in-gap E-field threshold amplitude of ∼10 MV/cm⁻¹, THz-induced field electron emission is observed as indicated by the field-induced electric current across the dipole antenna gap. Field emission occurs within a fraction of the driving THz period. Our analysis of the current (I) and incident electric field (E) is in agreement with a Millikan-Lauritsen analysis where log (I) exhibits a linear dependence on 1/E. Numerical estimates indicate that the electrons are accelerated to a value of approximately one tenth of the speed of light.