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

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

Blog Article

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 master-cock 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 In Ground Product (Lighting) 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.