Fig. 1. Small footprint and passive optoelectrode for electrophysiology and optogenetic applications.

a Schematic illustration of the neural probe, which is a needle device inserted into the brain cortex of an optogenetically modified mouse to study neural functions. The probe tip, which is the only part of the device inserted into the cortex, has a minimally invasive size for reduced brain damage and integrates both nanophotonic circuits and arrays of sensors for simultaneous high-spatiotemporal-resolution optical manipulation and readout of neural networks. We connect the probe to an external laser and electronics through the device interface area to access the tip circuit functions. b False-color scanning electron microscopy (SEM) image of the probe tip showing the integration of both arrays of sensors (yellow) and nanophotonic circuits and highlighting the length (1 mm), width (45 µm), and thickness (20 µm) of the tip. The scale bar is 50 μm. c Close-up image of the probe tip, showing the wires and electrodes (highlighted in yellow) as well as the underlying nanophotonic circuit with ring resonators. The scale bar is 20 μm. d Further close-up showing wires and electrodes on top of some nanophotonic components: the bus waveguide (highlighted with dashed green lines) and a ring resonator (dashed red circle). The scale bar is 5 μm