Small footprint optoelectrodes for simultaneous readout and passive light localization by the use of ring resonators

Abstract: Neural probes are in vivo invasive devices that combine electrophysiology and optogenetics to gain insight into how the brain operates, down to the single neuron and its network activity. Their integration of stimulation sites and sensors allows for recording and manipulating neurons` activity with a high spatiotemporal resolution. State of the art probes are limited by tradeoffs between their lateral dimension, the number of sensors, and the ability to selectively access independent stimulation sites. Here, we realize a highly scalable probe that features a three-dimensional integration of small footprint arrays of sensors and nanophotonic circuits and scales the density of sensors per cross-section by one order of magnitude with respect to state of the art devices. For the first time, we overcome the spatial limit of the nanophotonic circuit by coupling only one waveguide to numerous optical ring resonators as passive nanophotonic switches. With our strategy, we achieve accurate on-demand light localization while avoiding spatial demanding bundles of waveguides and demonstrate the feasibility of a proof of concept device and its additional scalability, towards high resolution and low damaging neural optoelectrodes.