Nonlinear polarization holography of nanoscale iridium films

Abstract

Attosecond nonlinear polarization spectroscopy refers to the subcycle-precise retrieval of the electric field of a femtosecond laser pulse together with the nonlinear polarization response that the laser pulse triggers in a sample. 
Here, we introduce a method that is all-optical and applicable to metal films. 
The method is called nonlinear polarization holography because it is based on the comparison of two time-domain holograms with and without a metal film on a substrate.
The working principle can be understood as the time-domain analog of holographic interferometry, in which the comparison of two spatial holograms reveals changes in an object's size and position with interferometric precision (i.e. to fractions of the wavelength). Analogously, nonlinear polarization holography provides subcycle precision (i.e. to fractions of the optical period).
Nonlinear polarization holography is used here to retrieve the time-domain nonlinear response of a nanoscale iridium film. Using density matrix calculations it is shown that the knowledge of the nonlinear response with subcycle precision allows distinguishing excitation and relaxation mechanisms of low-energetic electrons.

Light-Field-Controlled PHz Currents in Metals

“…The direct link to χ (3) is advantageous since, as a macroscopic quantity, the nonlinear susceptibility can be independently measured with, for example, a zscan method. At the same time, the metallic 2D heterostructures are considered to show exceptionally high χ (3) [26,27], which hints on their suitability for an ultrafast current generation medium. Indeed, our z-scan measurement of our samples yields an increasing nonlinear susceptibility as a function of the volume fraction, χ (3) (f ), see Fig.…”