Self-mixing effect inside the fiber ring laser with different fiber-ends

•Observe self-mixing signal inside the fiber ring laser with different fiber-ends.•Use the ABCD matrix for the calculation of coupling efficiency.•Simulation show a good agreement with the experiment results.

In this paper, a basic issue in the research of the coupling efficiency inside fiber ring laser self-mixing interference with different fiber-ends is discussed. From the experimental section, we observe waveforms of self-mixing signal inside the fiber ring laser with different fiber-ends. In the theoretical part, we analyze the laser self-mixing process in the Gaussian beam approximation and use the ABCD matrix under paraxial approximation for the calculation of coupling efficiency inside the fiber ring laser with different fiber-ends. Theoretical and experimental results indicate that different fiber-ends would form different characteristics of the laser self-mixing signal. Furthermore, the results of the comparison between theoretical and experimental results illustrate that the plane-end usually widely used in practical application of most self-mixing interference systems and could keep a required coupling efficiency in measurements. In addition, the pigtail with sphere-end could be suitable for the occasion of high requisition of good coupling efficiency and the pigtail with cone-end is suitable for the measurement of hyperfine structure and surface roughness.