The present invention provides an apparatus that includes an infrared (IR) light source having two or more wavelengths (e.g., a relatively broad wavelength-profile light source and/or a light source with a plurality of relatively narrowband wavelengths), wherein the different wavelengths have different tissue-penetration depths. The IR light provides optical stimulation of nerves to generate nerve-action potentials (NAPs) in one or more individual nerve cells, and/or compound nerve-action potentials (CNAPs) in a nerve bundle. In some embodiments, the stimulation of NAPs and CNAPs is used to restore hearing. In some embodiments, the broad wavelength profile extends the physical volume of tissue that is stimulated, thus homogenizing the spatial light-absorption profile of the stimulation light used, e.g., for optical triggering of NAPs and CNAPs in the cochlea.
