Ray tracing models for estimating light collection properties of microstructured tapered optical fibers for optical neural interfaces

ABSTRACT Tapered optical fibers (TFs) were recently employed for depth-resolved monitoring of functional fluorescence in sub-cortical brain structures, enabling light collection from groups of a few cells through small optical windows located on the taper edge [1]. Here we present a numerical model to estimate light collection properties of microstructured TFs implanted in scattering brain tissue. Ray tracing coupled with Henyey-Greenstein scattering model enables the estimation of both light collection and fluorescence excitation fields in three dimensions, whose combination is employed to retrieve the volume of tissue probed by the device.