Abstract
Two-color multiphoton emission from polycrystalline tungsten nanotips has been demonstrated using two-color laser fields. The two-color photoemission is assisted by a three-photon multicolor quantum channel, which leads to a twofold increase in quantum efficiency. Weak-field control of two-color multiphoton emission was achieved by changing the efficiency of the quantum channel with pulse delay. The result of this study complements two-color tunneling photoemission in strong fields, and has potential applications for nanowire-based photonic devices. Moreover, the demonstrated two-color multiphoton emission may be important for realizing ultrafast spin-polarized electron sources via optically injected spin current.
Highlights
Electron photoemission has played an important role in the advancement of ultrafast science [1, 2]
Laser parameters were set in the weakfield regime, so that multiphoton emission was dominant over tunneling photoemission [6]
The two-color multiphoton emission is assisted by a three-photon multicolor quantum channel
Summary
Electron photoemission has played an important role in the advancement of ultrafast science [1, 2]. Recent studies of photoelectrons demonstrate the feasibility of using tip-like nanostructures as ultrafast light detectors and ultrafast electron sources [3,4,5]. In these studies, carrier-envelope phase was used for ultrafast control of tunneling photoemission in strong fields. Carrier-envelope phase was used for ultrafast control of tunneling photoemission in strong fields Such methods are not effective in the weak-field regime, as photoemission in weak fields is accomplished through multiphoton processes [6]. The weak-field regime is especially important for nanotip photoemission because in this regime high repetition rates are accessible, which can lead to bright photoemission electron sources while avoiding laser induced damage
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