Jingdi Zhang1,2,a), Xiaoguang Zhao3,a), Kebin Fan3, Xiaoning Wang3,Gu-Feng Zhang1, Kun Geng2, Xin Zhang3,b) and Richard D. Averitt1,2,b)
HIDE AFFILIATIONS
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
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.
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