Generation of Bessel beam lattices by a single metasurface for neuronal activity recording in zebrafish larva

Bessel Beams (BBs) and BB lattices are structured-light excitation profiles frequently applied in material processing, nonlinear spectroscopy and in many fluorescence microscopy methods such as Light Sheet Microscopy (LSM). In LSM, BBs and BB-lattices offer wider excitation profiles, higher acquisition rate, enhanced resolution, and improved signal-to-noise ratio, while reducing the overall phototoxicity. However, this performance improvement typically comes at the cost of layout complexity and spatial constraints, originating from the optical arrangement required for obtaining BB features and for multiplexing the BB in a lattice of beamlets. Here, we introduce a novel method for encoding in a single flat element all the optical operations required to generate a BB lattice, including those of the excitation objective. We assessed the effective capabilities of this approach, using Meta-Surface (MS) technology to fabricate the corresponding flat optical element and to characterize its optical figures. Finally, we demonstrated its actual application in LSM, recording neuronal activity at cellular resolution in the zebrafish larval brain using fluorescence based neuronal activity reporters. In perspective, this approach, applied here for LSM, prompts a step forward in the BB versatility and in the BB application scenarios.