Before revision: The flat surface also allows a GRIN lens to be easily fused to an optical fiber, to produce collimated output, making it applicable for endoscopy as well as in vivo calcium imaging and optogenetic stimulation .
After revision: The flat surface also allows a GRIN lens to be easily optically aligned to aforin brain fiber, to produce collimated output, making it applicable for endoscopy as well as in vivo calcium imaging and optogenetic stimulation .