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Abstract

Recently, the emergence of a higher-energy structure (HES) due to a spatial inhomogeneity in the laser electric field, as is typically found close to a nanotip, was reported in Phys. Rev. Lett. 119, 053204 (2017). For practical applications, such as the characterization of near fields or the creation of localized sources of monoenergetic electron beamswith tunable energies, further insight into the nature of this higher-energy structure is needed. Here, we give a closed form analytical approximation to describe the movement of the electron in the inhomogeneous electric field. In particular, we derive a simple scaling law for the location of the HES peak and give a scheme to analytically tune the width of the peak, both of which will prove useful in optimizing the nanostructure size or geometry for creating the HES in experimental settings.