title: Nanostructured ultrafast silicon-tip optical field-emitter arrays.
abstract: Femtosecond ultrabright electron sources with spatially structured emission are an enabling technology for free-electron lasers, compact coherent X-ray sources, electron diffractive imaging, and attosecond science. In this work, we report the design, modeling, fabrication, and experimental characterization of a novel ultrafast optical field emission cathode comprised of a large (>100,000 tips), dense (4.6 million tips·cm(-2)), and highly uniform (<1 nm tip radius deviation) array of nanosharp high-aspect-ratio silicon columns. Such field emitters offer an attractive alternative to UV photocathodes while providing a direct means of structuring the emitted electron beam. Detailed measurements and simulations show pC electron bunches can be generated in the multiphoton and tunneling regime within a single optical cycle, enabling significant advances in electron diffractive imaging and coherent X-ray sources on a subfemtosecond time scale, not possible before. At high charge emission yields, a slow rollover in charge is explained as a combination of the onset of tunneling emission and the formation of a virtual cathode.
authors: Microsystems Technology Laboratories and ‡Department of Electrical Engineering and Computer Science and Research Laboratory of Electronics, Massachusetts Institute of Technology , 77 Massachusetts Avenue, Cambridge, Massachusetts 02139, United States.
authors: Michael E
authors: ME
authors: Swanwick
authors: Phillip D
authors: PD
authors: Keathley
authors: Arya
authors: A
authors: Fallahi
authors: Peter R
authors: PR
authors: Krogen
authors: Guillaume
authors: G
authors: Laurent
authors: Jeffrey
authors: J
authors: Moses
authors: Franz X
authors: FX
authors: Kärtner
authors: Luis F
authors: LF
authors: Velásquez-García
keywords: Strong-field photoemission; field emission; field emitter array; nanosharp; silicon emitters; ultrafast optics