Design and Construction of Three Infrared Ellipsometers for Thin-Film Research

The University of Dayton Research Institute (UDRI) has de-signed and built three infrared ellipsometers in support of the Air Force high energy laser program. One of these instruments is a conventional null-type ellipsometer for operation in the 3.39 to 4.00 um wavelength range. Ellipsometric parameters are determined with a precision of 0.01 ° at any angle of incidence from 20 ° to 85 °. Repeatability and absolute accuracy also approach 0.01 °, which yields optical constants accurate to 0.1 percent in some cases. All components are mounted on removable carriers for easy interchange, although operation is normally in the PCSA (polarizer, compensator, sample, analyzer) configuration. The system software has special provisions for the second instrument, which is also a null-type ellipsometer dedicated to monitoring vacuum deposited coatings in real time at 3.39 Am. The software can model nonideal components in the optical path using Jones or Mueller matrices and provide completely corrected data with a single zone measurement after the instrument is characterized. The third instrument is a rotating polarizer, automated ellipsometer tunable from 1 to 12µm. A dedicated computer operates the instrument and reduces data.