Sub-external cavity effect and elimination method in laser self-mixing interference wave plate measurement system

• Published in: Chinese physics B Vol. 27; no. 2; pp. 349 - 354
• Main Author: 牛海莎;牛燕雄;宋建军
• Format: Journal Article
• Language: English
• Published: Chinese Physical Society and IOP Publishing Ltd 01.02.2018
• Subjects: non-coated wave plate measurement; self-consistent model; self-mixing interference; 测量系统;干扰波;激光;混合;浪板;干扰系统;发芽技术;测量方法
• ISSN: 1674-1056; 2058-3834
• DOI: 10.1088/1674-1056/27/2/024201

Laser self-mixing interference（SMI） wave plate measurement method is a burgeoning technique for its simplicity and efficiency. But for the non-coated sample, the reflected light from the surface can seriously affect the measurement results.To analyze the reason theoretically, a self-consistent model for laser operation with a sub-external and an external cavity is established, and the sub-external cavity formed by the sample and a cavity mirror is proved to be the main error source.A synchronous tuning method is proposed to eliminate the sub-external cavity effect. Experiments are carried out on the synchronously tuning double external cavities self-mixing interference system, and the error of the system is in the range of -0.435°~0.387° compared with the ellipsometer. The research plays an important role in improving the performance and enlarging the application range of the laser self-mixing interference system.