Broadband femtosecond spectroscopic ellipsometry

• Published in: Review of scientific instruments Vol. 92; no. 3; pp. 033104 - 33117
• Main Authors: Richter, Steffen, Rebarz, Mateusz, Herrfurth, Oliver, Espinoza, Shirly, Schmidt-Grund, Rüdiger, Andreasson, Jakob
• Format: Journal Article
• Language: English
• Published: United States 01.03.2021
• ISSN: 0034-6748; 1089-7623
• DOI: 10.1063/5.0027219

We present a setup for time-resolved spectroscopic ellipsometry in a pump–probe scheme using femtosecond laser pulses. As a probe, the system deploys supercontinuum white light pulses that are delayed with respect to single-wavelength pump pulses. A polarizer–sample–compensator–analyzer configuration allows ellipsometric measurements by scanning the compensator azimuthal angle. The transient ellipsometric parameters are obtained from a series of reflectance-difference spectra that are measured for various pump–probe delays and polarization (compensator) settings. The setup is capable of performing time-resolved spectroscopic ellipsometry from the near-infrared through the visible to the near-ultraviolet spectral range at 1.3 eV–3.6 eV. The temporal resolution is on the order of 100 fs within a delay range of more than 5 ns. We analyze and discuss critical aspects such as fluctuations of the probe pulses and imperfections of the polarization optics and present strategies deployed for circumventing related issues.