Doppler-shifted laser self-mixing interferometry for enhanced detection sensitivity

• Published in: Journal of modern optics Vol. 66; no. 18; pp. 1796 - 1801
• Main Authors: Kou, Ke, Wang, Cuo, Zhang, Guanlei
• Format: Journal Article
• Language: English
• Published: Abingdon Taylor & Francis 24.10.2019; Taylor & Francis Ltd
• Subjects: Acoustooptical devices; Cost analysis; Doppler effect; Doppler shift; Interferometry; Lasers; Measurement techniques; Medical treatment; Modulators; relaxation oscillation frequency; Relaxation oscillations; Rotating disks; Self-mixing interferometry; sensitivity; Sensitivity enhancement; signal to noise ratio; Theoretical analysis
• ISSN: 0950-0340; 1362-3044
• DOI: 10.1080/09500340.2019.1674933

Laser self-mixing interferometry (SMI) is a well-known measurement technique having been applied to the fields of geometrical quantities detection, medical treatment and industry manufacturing. Its detection sensitivity can be improved by frequency shifting towards the laser's relaxation oscillation frequency (ROF), which has always been implemented by a pair of acousto-optic modulators (AOM). This manuscript presents a novel method based on Doppler effect for frequency shifting, which is based on a rotating disk and has the advantages of convenient adjustment and low cost. The theoretical analysis in the form of Doppler shift and time-delayed rate equations is followed, and simulative and experimental results are included to prove its validity. To our knowledge, this technique has not been used in practice till now, and the proposed structure, with these advantages, can find significant applications in designing high performance SMI sensors, and can extend SMI measurement to more kinds of non-cooperative surfaces.