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Fiber-based modulated optical reflectance configuration allowing for offset pump and probe beams
A Fleming1, C Folsom1, C Jensen1
1Department of Mechanical and Aerospace Engineering, Utah State University, Logan, Utah 84322, USA.
The Review of Scientific Instruments
|January 3, 2017
Summary
A novel fiber-optic system measures thermal diffusivity using modulated laser heating and optical reflectance. This technique accurately determines thermal properties for materials like Germanium and Silicon Carbide, crucial for advanced material science applications.
Area of Science:
- Materials Science and Engineering
- Optical Physics
- Thermal Analysis
Background:
- Accurate measurement of thermal diffusivity is critical for understanding and optimizing material performance in various applications.
- Existing methods for thermal diffusivity measurement can be complex, time-consuming, or unsuitable for in-situ analysis.
- Development of non-contact or minimally invasive techniques is desirable for precise material characterization.
Purpose of the Study:
- To develop and validate a new fiber-based modulated optical reflectance system for measuring thermal diffusivity.
- To assess the system's performance and accuracy for different materials, including semiconductors and insulators.
- To investigate the influence of measurement configuration (contact vs. non-contact) on accuracy.
Main Methods:
- A fiber-based setup employing a pump laser for periodic heating and a probe laser for optical reflectance detection.
- The system utilizes a ceramic ferrule to maintain a fixed separation between the pump and probe fibers.
- Thermal diffusivity is calculated from the phase lag between the modulated heat input and the sample's temperature response.
Main Results:
- The system achieved measurements for Germanium (Ge) and Silicon Carbide (SiC) within 10% of established literature values.
- Measurements on Silicon Dioxide (SiO2) showed a ~100% deviation when the ferrule was in direct contact with the sample.
- Non-contact SiO2 measurements yielded results with less than 2% difference from literature values, highlighting the impact of contact.
Conclusions:
- The developed fiber-based modulated optical reflectance technique is a viable method for accurate thermal diffusivity measurements.
- The system demonstrates high accuracy for various materials, particularly in non-contact configurations.
- Direct contact can introduce parallel heat transfer pathways, affecting measurement accuracy, especially for insulating materials like SiO2.
