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Beam diameter thresholds as applying light depolarization for effective submicron and micron root mean square
Applied Optics
|October 20, 2017
Summary
We developed a compact laser instrument to study light depolarization (LDP) and its effect on surface roughness measurement. Smaller beam spot sizes (BSS) provide higher sensitivity for precise roughness analysis.
Area of Science:
- Optics and Photonics
- Materials Science
- Surface Metrology
Background:
- Light Depolarization (LDP) is crucial for understanding light-matter interactions.
- Accurate surface roughness (Rq) evaluation is vital in precision engineering.
Purpose of the Study:
- To investigate the microscopic mechanisms of LDP.
- To determine the effect of beam spot size (BSS) on LDP-based Rq measurements.
- To develop a compact, portable instrument for online roughness testing.
Main Methods:
- Developed a compact laser instrument (λ=632.8 nm) with adjustable BSS (≥18 μm).
- Examined six nickel plate samples with Rq ranging from 42 nm to 2.3 μm.
- Performed off-specular inspections with BSS adjusted from 20 μm to 650 μm.
Main Results:
- BSS ≤ 40 μm (60λ) achieved 10-nm-level Rq sensitivity.
- BSS ≥ 140 μm (220λ) showed ~100 times weaker sensitivity.
- Demonstrated instructional significance of BSS for 10 nm and 1 μm Rq analyses.
Conclusions:
- BSS significantly impacts LDP-based surface roughness measurement sensitivity.
- The developed instrument offers high potential for LDP analysis and online roughness testing due to its simplicity, portability, and low cost.
