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Field emitters are microfabricated sharp tip structures that facilitate the field emission process by concentrating the field at the tip. P- type Si based filed emitter arrays (FEAs) which, unlike metallic tips, exhibit a high photo- sensitivity saturation regime where the field emission current is limited due to carrier depletion and thus can be optically modulated. Optically modulating a gated p-Si FEA by ultra-short pulses can bypass the large gate-to-cathode capacitance in electrically gated cathodes thus potentially can generate ultra-short electron bunches as a cold cathode in Microwave Vacuum Electronics Devices (MVEDs) applications. We demonstrated optical-gating gated p-Si FEA photocathodes wirh a mode-locked laser having 110 fs rise time achieved a drift transit time spread (TTS) limited response of 40 ps rise/fall time. A proposed temporal model explianed the mechanisms of photoresponse for gatde p-Si FEA photocathodes. We envision proposed p-i-n based FEA photocathodes with backside irradiation enables near unity quantum efficiency TTS limited photoresponse. These findings are opening the way for a new generation of MVEDs.

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Dr. Chiang received his B.S. and M.S. from National Taiwan University of Science and Technology, and his Ph.D. from University of California, Davis in 2007. He joined National Institute of Standards and Technology, Boulder, from 2008 to 2009. Since 2009 he has joined Electronics Engineering at National Changhua University of Education.

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