This is personal blog of Premysl Marsik from University of Fribourg in Switzerland. The blog should cover topics from ellipsometry, particularly infrared ellipsometry and time-domain terahertz (THz) ellipsometry. Premysl Marsik works in the Spectroscopic Ellipsometry lab in the Magnetism and Superconductivity group of Christian Bernhard at the Physics department of UniFr.