Optical measurements on a budget: A 3D-printed ellipsometer

Abstract

Ellipsometry is an optical analysis technique that is useful for characterizing the physical properties of a thin-film system. Light reflected from a sample surface undergoes a change in polarization due to phase delay and anisotropic reflection. This enables one to perform non-destructive measurements of film thickness, surface roughness, refractive index, and other optical constants. Ellipsometric techniques are particularly convenient for characterizing coatings or films in the semiconductor and optics industries. However, these techniques may be inaccessible to undergraduate students and educators due to the prohibitive cost of ellipsometers and similar instrumentation. In response to this roadblock, we describe the construction of a simple, inexpensive, manually operated, rotating analyzer ellipsometer (RAE). Required materials include a laser pointer, polarizing film, photometric detector, and a 3D-printed opto-mechanical framework, which are all readily accessible at most institutions. The instrument's performance was evaluated by comparing thickness measurements of tetraethyl orthosilicate films to those determined by a commercially available reflectometer. An average film thickness difference of 0.77% was measured using the two instruments.