Time-Resolved Absorption Spectroscopy

Abstract

This dissertation work emphasizes on the exciton energy shift that is induced by femtosecond light pulses. At equilibrium, the exciton energy level in monolayer TMDs sits in the visible regime, e.g., E 0 = 2 eV in monolayer WS2. In order to detect this energy shift, we need a broadband probe pulse that is centered in the visible spectrum. White light continuum generation is a nonlinear optical process capable of producing such broadband light pulse between 500 and 700 nm (ℏω = 1.8 − 2.4 eV). In this chapter, we will discuss about time-resolved absorption spectroscopy setup (or simply transient absorption) that utilizes white light continuum to probe the exciton energy shift in monolayer TMDs. In the first section, we will show the overview of the transient absorption setup. In later sections, we will discuss in more details about (1) laser amplifier, (2) optical parametric amplifier, and (3) white light continuum generation. Finally, we will discuss about the data analysis based on the optical physics of monolayer materials on a transparent substrate.