ABSTRACT
Optical neural stimulation has become a key neurophotonic technology, providing multiple benefits over electrical stimulation due to its non-contact nature, high spatiotemporal resolution, and potential for cell-type selective targeting. The demonstrations of single-photon Holographic Optical Neural Interfaces for optogenetic stimulation included selectively activating multiple retinal ganglion cells as a path to restore vision lost following photoreceptor degeneration and single-photon activation of cultured neurons and HEK cells. The fundamental properties of the optical elements comprising the system and primarily the spatial light modulator will ultimately determine its performance. The experimentally measured FWHM is slightly larger than the theoretically expected FWHM for a Gaussian beam due to physical limitations of the optical system and due to the rapid phase variations of the pattern generated on the grating. Mechanical averaging can be accomplished by adding an optical element such as a rotating diffuser that pseudo-randomly scrambles the resulting phases and reduces speckle contrast.
