An exact formulation for ultrafast electron emission due to a dc bias and a laser field

This paper presents an analytical theory of electron emission from a metal surface subjected to an arbitrary combination of a dc electric field and a laser electric field. We solve the time-dependent Schrödinger equation exactly, and show that short electron bunches may be produced by a relatively weak laser field with a strong dc bias field. Our exact solution is valid for arbitrary laser frequency and metal properties (work function and Fermi level). Various emission mechanisms, including multiphoton absorption or emission, optical or dc field emission, single-photon induced over-barrier emission, and various combinations of them, are all captured in a single formulation.