Revisiting Photoemission via Transient Work Function Gating*

We offer a new perspective to study the interplay between intrinsic emittance and quantum efficiency (QE), and the challenges associated with tailoring the phase-space of electrons. This alternative photoemission mechanism, coined as Transient Work Function Gating (TWFG)[1], has the potential to circumvent the long-standing trade-off in photoemission between intrinsic emittance and QE. TWFG is theorized to be able to temporally and energetically control the carrier density in near-threshold photoemission using, in addition to a photoemission laser, both strong-field single-cycle[2] and multi-cycle[3] terahertz fields. We will examine TWFG in the production of electron beams for ultrafast electron sources, linear accelerators, and X-ray free-electron lasers.

[1] Carbajo, Sergio. "Transient Work Function Gating: A New Photoemission Regime." Journal of Applied Physics 128, 023102 (2020);
[2] Wu, Xiaojun, et al. "Terahertz generation in lithium niobate driven by Ti: sapphire laser pulses and its limitations." Optics letters 39.18 (2014): 5403-5406.
[3] Carbajo, Sergio, et al. "Efficient narrowband terahertz generation in cryogenically cooled periodically poled lithium niobate." Optics letters 40.24 (2015): 5762-5765.