Optical depth sectioning in self-mixing lasers for biomedical applications

Abstract

Illumination in scattering media provides a general means to provide optical diagnosis in a noninvasive, painless and low cost approach, which has pushed forward the interest of the field both in biomedical and industrial applications. Several biophotonics techniques are based on the use of the therapeutic window of skin, where diffusion of light is dominant and the classical geometrical optics approach gets lost, with only radiometric methods being valid in practice. A comparable analysis is valid for industrial applications where the analysis of inclusions in scattering e

Self-mixing interferometry is a measurement technique based on the effect that in a laser the reinjection of emitted light back-reflected into its cavity has on the the properties of the laser itself. In diode lasers, optical feedback effects are particularly powerful, and can be employed as a powerful metrological tool. Due to its self-alignment and lack of any external elements, self-mixing interferometry is very robust and low cost, and can offer an adequate trade-off between performance and cost for a wide range of sensing applications. In this work, self-mixing interferometry has been proposed, studied and implemented for vibrometry and flowmetry in combination with conventional microscopy to provide the former technique with the lateral and axial resolution of the latter. Besides, the self-mixing interferometry phenomena has been extensively reviewed, and a model for complex interferometric external cavities has been developed.