Effect of Linewidth Enhancement Factor on Fringe in a Self-Mixing Signal and Improved Estimation of Feedback Factor in Laser Diode

• Published in: IEEE access Vol. 7; pp. 28886 - 28893
• Main Authors: Kim, Cholhyon, Lee, Cholman, O, Kwonhyok
• Format: Journal Article
• Language: English
• Published: Piscataway IEEE 2019; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Analytical models; behavioral model; Cavity resonators; Displacement measurement; Estimation; fast estimation; Hysteresis; Laser beams; laser diode; Lasers; Low-cost self-mixing sensor; Optical feedback; optical feedback factor; Phase unwrapping; Semiconductor lasers; Shape
• DOI: 10.1109/ACCESS.2018.2883475
• ISSN: 2169-3536

The optical output power of a laser diode is modulated by the self-mixing effect when the optical beam is back-reflected or back-scattered into the laser cavity by a target. The optical feedback factor C is the most important one that defines the feature of the self-mixing signals (SMSs). And the estimation of C is indispensable for the displacement reconstruction by the phase unwrapping method because it is impossible to reconstruct the displacement with sub-wavelength resolution, provided the exact value of C is unknown. Unfortunately, C is subject to constant change during the measurement and, what is worse; its estimation is usually very time-consuming. This paper studies the feature of a high and low fringe of SMSs in moderate and strong feedback regime and the effect of the feedback factor and the linewidth enhancement factor on the fringes and presents a simple approach to the estimation of C when C > 1.5 based on the behavioral model proposed by Plantier et al. In particular, the novel approach enables fast direct estimation of C because it is based on analytic relations between C and the amplitudes of the high and low peak in SMSs.