In a broad sense, photonics is the science of light (photon) generation, detection, and manipulation through emission, transmission, modulation, switching, amplification, and signal processing. Although photonic applications can cover the entire light spectrum, most lie in the range of visible and near-infrared light. Photonic applications started in earnest in the 1960s with the invention of the laser diode and optical fibers. Neurophotonics, photonics for probing and activating the nervous system, has been used in biomedical applications for quite a while and the use of this modality in the central nervous system stimulation and imaging has been a major field of research. Lately, it has found its way into the peripheral nervous system (PNS) stimulation and imaging. The PNS is the part of the nervous system that consists of the nerves and ganglia outside the brain and spinal cord. Its function is to connect the brain to the limbs and organs successfully, essentially creating a communication bridge between them. Although, for peripheral nerve stimulation, electrical methods have been the gold standard so far, they have some inherent limitations such as reverse recruitment of the larger diameter nerve fibers by the electric field. Optical methods are transcending these limitations. There has long been interest in using light to influence the behavior of neurons partially and particularly due to its noninvasive nature. Light can trigger action potentials similarly to the ones obtained through electrical stimulation. This book chapter reviews different photonics applications in peripheral nerve stimulation and imaging.
