**Olaf Stenzel 1,\*, Ste**ff**en Wilbrandt 1, Christian Mühlig <sup>2</sup> and Sven Schröder <sup>1</sup>**


Received: 20 December 2019; Accepted: 7 January 2020; Published: 9 January 2020

**Abstract:** Titanium dioxide films were prepared by plasma ion-assisted electron beam evaporation. Linear optical properties were investigated in terms of spectrophotometry using the beta-distributed oscillator (ß\_do) model as a parametrized dispersion law. The nonlinear two-photon absorption coefficient of titanium dioxide was determined by means of the laser-induced deflection technique at a wavelength of 800 nm. The obtained values of (2–5) <sup>×</sup> <sup>10</sup>−<sup>11</sup> cm/W were consistent with published experimental values for rutile as well as for simulations performed in the frames of the ß\_do and Sheik–Bahae models.

**Keywords:** optical coatings; titanium dioxide; optical constants; two-photon absorption; nonlinear refraction; scattering; laser-induced deflection; absorption measurement
