Optogenetic methods developed over the past decade enable unprecedented optical activation and silencing of specific neuronal cell types. However, light scattering in neural tissue precludes illuminating areas deep within the brain via free-space optics; this has impeded employing optogenetics universally. Here, we report an approach surmounting this significant limitation. We realize implantable, ultranarrow, silicon-based photonic probes enabling the delivery of complex illumination patterns deep within brain tissue. Our approach combines methods from integrated nanophotonics and microelectromechanical systems, to yield photonic probes that are robust, scalable, and readily producible en masse. Their minute cross sections minimize tissue displacement upon probe implantation. We functionally validate one probe design in vivo with mice expressing channelrhodopsin-2. Highly local optogenetic neural activation is demonstrated by recording the induced response—both by extracellular electrical recordings in the hippocampus and by two-photon functional imaging in the cortex of mice coexpressing GCaMP6.
In this paper we propose using Array Waveguide Gratings (AWGs), working in the visible range, in order
to implement the technique of Wavelength-Division-(de)Multiplexing for multi-point stimulation of deep-brain
neurons. We've developed a CMOS compatible fabrication process and fabricated two sets of AWGs, working in
the red and blue wavelengths. Experimental data demonstrating the functionality of these AWGs is presented.