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Uncertainty Estimation for the Brillouin Frequency Shift Measurement Using a Scanning Tandem Fabry-Pérot
Patrice Salzenstein1, Thomas Y Wu2
1Centre National de la Recherche Scientifique (CNRS), Franche-Comté Electronique Mécanique Thermique Optique Sciences et Technologies (FEMTO-ST) Institute, Université de Franche-Comté (UFC), 25030 Besançon, France.
Micromachines
|July 29, 2023
Summary
This study details a Brillouin light scattering (BLS) spectrometer for material analysis. The system accurately measures material properties, like the longitudinal modulus, with high precision, improving upon existing methods.
Area of Science:
- Materials Science
- Spectroscopy
- Metrology
Background:
- Accurate measurement of material parameters requires precise determination of Brillouin scattering shift frequencies.
- Existing methods for material characterization have limitations in measurement uncertainty.
Purpose of the Study:
- To describe the operational principles of a Brillouin light scattering (BLS) spectrometer utilizing a high-power laser and scanning tandem Fabry-Pérot interferometer (TFPI).
- To analyze uncertainty components in the BLS spectrometer according to the Guide to the Expression of Uncertainty in Measurement (GUM).
- To evaluate the spectrometer's capability for material characterization, specifically for polymethyl methacrylate (PMMA).
Main Methods:
- Utilized a Brillouin light scattering (BLS) spectrometer equipped with a high-power laser and a scanning tandem Fabry-Pérot interferometer (TFPI).
- Performed detailed uncertainty analysis following the Guide to the Expression of Uncertainty in Measurement (GUM) guidelines.
- Measured and calculated Brillouin frequency shifts for polymethyl methacrylate (PMMA) to validate the system.
Main Results:
- The expanded relative uncertainty for the measured Brillouin frequency shift of PMMA was determined to be 0.26% (15.70 GHz).
- The calculated Brillouin frequency shift for PMMA was 15.44 GHz with an expanded relative uncertainty of 2.13%.
- The TFPI-based BLS spectrometer achieved a 1.9% expanded uncertainty for longitudinal modulus measurement, outperforming the ultrasonic velocity-based method (2.9%).
Conclusions:
- Measured and calculated Brillouin frequency shifts for PMMA are in agreement within their expanded uncertainties, validating the spectrometer's accuracy.
- The TFPI-based BLS spectrometer offers a precise method for material characterization, particularly for determining the longitudinal modulus.
- This advanced BLS system provides a more accurate alternative to ultrasonic methods for measuring material properties.
