Browsing by Author "Tsai, FH"

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Calibrations of phase modulation amplitude of photoelastic modulator
(2004-02-01)
Wang, MW
;
Chao, YF
;
Leou, KC
;
Tsai, FH
;
Lin, TL
A multiple harmonic intensity ratio technique is proposed for calibrating the modulation amplitude (Delta(0)) of a photoelastic modulator (PEM). A data acquisition system is utilized to investigate the frequency response of this technique. Delta(0) determined by this technique is independent of frequency, which is proved using the reflection and transmission setups. In addition to confirm our calibration using the digitized oscilloscope waveform, we also obtain a set of ellipsometric parameters under various values of Delta(0) before and after calibration. We also introduce a correction factor to correct the effect caused by the shift of the modulation amplitude in the process of etching. An optical thick film is used to calibrate Delta(0) using PEM ellipsometry, and its refractive index and extinction coefficient are also obtained in etching. Finally, we suggest the use of the traces of the ellipsometric parameters under various thicknesses for monitoring instead of calculating the thickness in real time.
In situ calibration technique for photoelastic modulator in ellipsometry
(2004-05-01)
Wang, MW
;
Tsai, FH
;
Chao, YF
;
光電工程學系
;
Department of Photonics
The modulation amplitude of a phase modulator is calibrated under a fixed incident angle in photoelastic modulation (PEM) ellipsometry. In addition to its modulation amplitude (Delta(o)), we also calibrated its static phase retardation at 632.8 nm. The ellipsometric parameters of a sample were measured by a multiple harmonic intensity ratio technique and proved that ellipsometric parameters can be obtained under various modulation amplitudes. Since the physical size of PEM is constant, we calibrated the modulation amplitude at multiple wavelengths by setting the Delta(o) value at 0.383 for 568.2 nm. These calibrations provided enough information for establishing an in situ/real time spectroscopic ellipsometry. (C) 2003 Elsevier B.V. All rights reserved.