Brightness of femtosecond nonequilibrium photoemission in metallic photocathodes at wavelengths near the photoemission threshold

Jai Kwan Bae, Ivan Bazarov, Pietro Musumeci, Siddharth Karkare, Howard Padmore, Jared Maxson

Research output: Contribution to journalArticle

1 Scopus citations

Abstract

The operation of photoemission electron sources with wavelengths near the photoemission threshold has been shown to dramatically decrease the minimum achievable photocathode emittance, but at the cost of significantly reduced quantum efficiency (QE). In this work, we show that for femtosecond laser and electron pulses, the increase in required laser intensities due to the low QE drives the photocathode electronic distribution far from static equilibrium. We adapt an existing dynamic model of the electron occupation under high intensity laser illumination to predict the time-dependent effects of the nonequilibrium electron distribution on the QE, mean transverse energy (MTE), and emission brightness of metal photocathodes. We find that multiphoton photoemission dramatically alters the MTE as compared to thermal equilibrium models, causing the MTE to no longer be a monotonic function of photon excess energy.

Original languageEnglish (US)
Article number244903
JournalJournal of Applied Physics
Volume124
Issue number24
DOIs
StatePublished - Dec 28 2018
Externally publishedYes

ASJC Scopus subject areas

  • Physics and Astronomy(all)

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