Journal of Infrared and Millimeter Waves, Volume. 43, Issue 3, 354(2024)
Non-destructive thickness measurement with micron level accuracy based on a 4.3-THz quantum-cascade laser
Fig. 1. Terahertz homodyne detection system:(a) Schematic of the terahertz light path;(b) Photos of the experimental setup
Fig. 2. The measured terahertz beam spot including both the reference light and the interference fringes
Fig. 3. Schematic diagram of the optical path when the terahertz beam passes through the sample
Fig. 4. Theoretical curves of transmission phase (φ) changing with sample rotation angle (θ) under different thickness (T) conditions
Fig. 5. Thickness measurement results of silicon wafers numbered 1 (a),2 (b),and 3 (c) based on optical microscopes,as well as the measured length of a 1 mm standard microscale plate (d)
Fig. 6. Experimental results of transmission phase (φ) with the rotation angle (θ) after the terahertz light passes through the wafer (1+2) and the wafer (1+2+3)
Fig. 7. Variation of the calculated RMSE with the fitting thickness:(a) wafer (1+2);(b) wafer (1+2+3)
Fig. 8. Experimental (solid circle) and fitting (solid line) transmission phase with different rotation angle
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Hong-Yi LI, Zhi-Yong TAN, Wen-Jian WAN, Jun-Cheng CAO. Non-destructive thickness measurement with micron level accuracy based on a 4.3-THz quantum-cascade laser[J]. Journal of Infrared and Millimeter Waves, 2024, 43(3): 354
Category: Research Articles
Received: Aug. 28, 2023
Accepted: --
Published Online: Apr. 29, 2024
The Author Email: Zhi-Yong TAN (zytan@mail.sim.ac.cn), Jun-Cheng CAO (jccao@mail.sim.ac.cn)