What is the difference between the two? I see them frequently listed together in conference descriptions but can't seem to find anything that clearly explains the difference.
Neurophotonics refers to the use of light to study the brain, including measurement (i.e. microscopy, including the use of fluorescent molecules that allow measurement of ions or voltages in live tissue, but also including histological techniques) and manipulation (using light to activate, inactivate, modulate, etc neural activity).
Optogenetics refers to the use of genetically encoded (whether delivered via virus or in a transgenic animal) constructs that respond to light and are introduced into cells where they are not normally found, often neurons. Neurophotonics is a broad term that would include optogenetics.
In my personal opinion, optogenetics is a fairly specific term that is useful, though it certainly has some popular buzz around it. Neurophotonics is a new buzzword that encompasses a lot of techniques that have been around a long time, and while these techniques are constantly improved upon, the neurophotonics label isn't really necessary (but sounds fun).