Self-mixing interference in a diode laser: experimental observations and theoretical analysis

Abstract

The experimental results of an investigation of self-mixing effects or backscatter modulation in diode lasers coupled with a simple theoretical analysis are presented. The laser is used to send light, either in free space or through an optical fiber, to a movable target from which the optical backscatter is detected and fed back into the laser. In the experiment three significant conclusions are drawn: (1) self-mixing interference is not dependent on the coherence length of the laser, (2) the interference is not dependent on the use of a single-mode or multimode laser as the source, and (3) the interference is independent of the type of fiber employed, i.e., whether it is single mode or multimode. A comparison of this kind of interference with that in a conventional interferometer shows that self-mixing interference has the same phase sensitivity as that of the conventional arrangement, the modulation depth of the interference is comparable with that of a conventional interferometer, and the direction of the phase movement can be obtained from the interference signal. The above factors have implications for the optical sensing of a wide range of physical parameters. Several applications of the method are discussed that highlight the significant advantages of simplicity, compactness, and robustness as well as the self-aligning and self-detecting abilities of fiber-based self-mixing interferometry when compared with the use of conventional interference methods.

Differential optical feedback interferometry for the measurement of nanometric displacements

“…Early studies on the subject dated from the 1980s, when several research groups [1][2][3] studied the behavior of laser diodes (LD) subjected to optical feedback. These early studies gave rise to a series of applications being the most representatives, the measurement of micrometric displacements [4,5], velocity [6] and absolute distance [7].…”

Single high-order round-trip feedback effects in orthogonally polarized dual frequency laser

“…The optical feedback in lasers, also called self-mixing interference, can be realized by the laser output coupled back into its cavity from an external reflector [1][2][3][4]. Compared with conventional interference systems, optical feedback systems have the advantages of simplicity, compactness, self-alignment and low cost [5,6].…”

Eliminating noises contained in sensing signals from a self-mixing laser diode

“…When a small fraction of light emitted by a laser diode (LD) is reflected or backscattered by an external target and reenters the laser internal cavity, both the amplitude and the frequency of the emitted laser power can be changed [1][2][3]. In this case, the laser diode is called a self-mixing LD (SMLD) which can be used as a sensor for obtaining metrological quantities associated to the external target as well as the parameters of the LD.…”

“…In this case, the laser diode is called a self-mixing LD (SMLD) which can be used as a sensor for obtaining metrological quantities associated to the external target as well as the parameters of the LD. Experimental set-ups suitably oriented to such sensing have been devised, and theoretical analysis proposed accordingly [2][3][4][5][6][7][8]. A typical SMLD sensing system is depicted in Figure 1.…”