Noninvasive photonic sensing of glucose in blood stream

In this chapter, we review several photonic methods, which were investigated in our group and which are based on temporal-spatial analysis of the collected speckle field, for sensing of glucose in bloodstream. First, we will present remote optical approach for measuring nano vibrations generated in the skin due to the changes in the bloodstream parameters as a function of the glucose concentration in the blood. We will show that these temporal-spatial vibration-related changes can be analyzed with different machine learning algorithms (e.g., random forest) to enhance the sensitivity of the measurements. Later, we will present the potential of Faraday rotation effect, in which the polarization of linearly polarized light is rotated when scattered from materials exhibiting this effect while being exposed to a magnetic field to evaluate glucose levels. Furthermore, we will show an experimental approach in which excited acoustic waves are generated and change the refractive index of the glucose solution. These changes are monitored via remote sensing of temporal speckle size variations. Finally, we will present the remote clinical approach for continuous monitoring of diabetic foot patients via laser contrast analysis.