In recent years, numerous methods have been sought for developing novel solutions to counter neurodegenerative diseases.
An objective that is being investigated by researchers is to develop cortical implants that are able to wirelessly stimulate
neurons at the single cell level. This is a major development compared to current solutions that use electrodes, which
are only able to target a population of neurons, or optogenetics, which requires optical fiber-leads to be embedded deep
into the brain. In this direction, the concept of wireless optogenetic nanonetworks has been recently introduced. In
such architecture, miniature devices are implanted in the cortex for neuronal stimulation through optogenetics. One of
the aspects that will determine the topology and performance of wireless optogenetic nanonetworks is related to light
propagation in genetically-engineered neurons. In this paper, a channel model that captures the peculiarities of light
propagation in neurons is developed. First, the light propagation behavior using the modified Beer-Lambert law is analyzed
based on the photon transport through the nervous tissue. This includes analyzing the scattering light diffraction and
diffusive reflection that results from the absorption of neural cell chromophores, as well as validating the results by means
of extensive multiphysics simulations. Then, analysis is conducted on the path loss through cells at different layers of the
cortex by taking into account the multi-path phenomenon. Results show that there is a light focusing effect in the soma of
neurons that can potentially help the to stimulate the target cells.