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25 February 2010 A small and fast SCPEM-based ellipsometer
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Proceedings Volume 7598, Optical Components and Materials VII; 75981T (2010) https://doi.org/10.1117/12.841690
Event: SPIE OPTO, 2010, San Francisco, California, United States
Abstract
We propose a small and fast ellipsometer with a basic layout similar to that of conventional ellipsometers using photo-elastic modulators (PEM) oscillating with 50 kHz. A conventional PEM is rather large, ~10×20×100mm, since it consists of one piece of glass and an actuator. Both parts are carefully adjusted to the desired frequency and then glued together. We replace such a standard modulator by a 127 kHz Single Crystal Photo-Elastic Modulator (SCPEM), a LiTaO3-crystal with a size of 20.6×7.5×5mm. The polarization of light that travels through this crystal is strongly modulated. The modulated light is reflected from the sample, passes a polarizer and hits a detector. Its signal is split into the dc-value and the amplitudes of the 1st and 2nd harmonic of the modulation frequency. These values lead via simple formulas to the ellipsometric parameters. Usually a Lock-In-Amplifier is used here, whereas we propose an automated digital processing based on a fast analog to digital converter controlled by a highly flexible Field Programmable Gate Array (FPGA). This and the extremely compact and efficient polarization modulation allow fast ellipsometric measurements as needed in high volume manufacturing of optics.
© (2010) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
F. Bammer, R. Petkovšek, J. Možina, and J. Petelin "A small and fast SCPEM-based ellipsometer", Proc. SPIE 7598, Optical Components and Materials VII, 75981T (25 February 2010); https://doi.org/10.1117/12.841690
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