Optical Time-Resolved Microscopy on Few-Atoms-Thick Materials

Abstract

In the past decade, the emergence of ultrathin 2D films consisting of only a few atomic layers deposited on various substrates sparked new ideas and research. This Perspective provides a nonexhaustive review of utilizing ultrafast optical pump−probe microscopy and the models for fitting experimental data that emerged in the past few years. We will focus on retrieving optically induced modifications of material parameters from pump−probe data on 2D materials, involving the inversion of Maxwell's equations and discussing new methods to localize optical interactions to capture the response of 2D films with increased resolution and sensitivity. These areas represent promising avenues for advancing our understanding of the dynamic behavior of ultrathin 2D films and their response to ultrafast optically induced transients.

Transient Absorption Spectroscopy of Films: Impact of Refractive Index

“…Consequently, the change in the sample’s refractive properties upon the dye’s photoexcitation event can be neglected. However, this is not necessarily the case for condensed matter, such as molecular or semiconductor films, in which the density of “excited species” is large enough such that the change in refractive properties may have a significant effect on the sample TA response. − …”

Quantitative Complex Refractive Index Changes in Thin Films: A Pump–Probe Spectroscopy Analysis Approach

“…To date, there have been a number of experimental and theoretical investigations into light-induced changes of the complex refractive index in thin films. ,,,, These studies have even extended to atomic layers of materials, with particular emphasis on situations where reflection phenomena are prominent . The methods demonstrated in these studies are applicable when access to both the differential transmission and reflection spectra of the probe is available.…”