Exact Analytical Solution for Pulsed Laser Induced Photoemission from Biased Surfaces

Abstract

Ultrafast laser-induced electron emission from nanostructures is fundamentally important to the development of coherent electron sources, ultrafast electron microscopy, and novel nano-vacuum devices [1] - [3] . For ultrashort pulsed laser induced photoemission, numerical simulations are typically implemented to study the emission property. Simplified Fowler-Nordheim based models are widely used to calculate the photoemission rate, but it works only in the strong optical field regime. To clearly reveal the underlying emission characteristics in different emission regimes under ultrashort pulsed condition, we construct an exact analytical solution for photoelectron emission from a dc-biased surface illuminated by laser pulses, by solving the time-dependent Schrödinger equation [4] - [7] . The model is valid for arbitrary pulse length from sub-cycle to CW excitation, and for arbitrary pulse repetition rate. The single formulation is valid from photon-driven electron emission in low intensity optical fields to field-driven emission in high intensity optical fields. Our calculations reveal the coherent interaction between neighboring laser pulses on the photoelectron emission, and well recover the experimentally observed sinusoidal carrier-envelope-phase modulation to energy spectra [8] and vanishing carrier-envelope-phase sensitivity of photoemission charge in the optical-field regime [9] . We also find adding a large dc field to the photoemitter is able to greatly enhance the photoemission current and significantly shorten the electron emission pulse.