Influence of linewidth enhancement factor \(\alpha \) on self-mixing interferometry in solid-state lasers


Up to now, laser self-mixing interferometry (SMI) has been widely applied to numerous scientific and industry fields. A easily negligible parameter, linewidth enhancement factor \(\alpha \), influences the inclination of SMI signals, and larger \(\alpha \) generally indicates more inclined fringes. It is demonstrated in the paper that solid-state lasers (SSL) have smaller linewidth enhancement factors compared with semiconductor ones, which interrupt the movement reconstruction of external targets. For Nd:YAG SSLs, \(\alpha \) is experimentally analyzed to be around one, resulting in less tilted SMI fringes, and the direction discrimination property of SMI becomes less obvious even when a smooth target supplies more amount of feedback light. In the Nd:YAG SSL scheme and for harmonic vibrations, a simple and effective method is also proposed to obtain the frequency and amplitude information of external targets. Simulations and experiments show that the method can achieve the frequency accuracy within 1% and the amplitude accuracy better than 3%.

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This work was supported by National Natural Science Foundation of China (Program No. 61803302), Natural Science Foundation of Shaanxi Province (Program No. 2017JQ6062) and Natural Science Foundation of Shaanxi Provincial Department of Education (Program No. 19JK0589).

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Correspondence to Ke Kou.

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Kou, K., Wang, C. Influence of linewidth enhancement factor \(\alpha \) on self-mixing interferometry in solid-state lasers. Opt Rev 28, 99–105 (2021).

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  • Laser self-mixing interferometry
  • Linewidth enhancement factor
  • Harmonic vibration