Abstract
Implantable silicon neural probes with integrated nanophotonic waveguides can deliver patterned dynamic illumination into brain tissue at depth. Here, we introduce neural probes with integrated optical phased arrays and demonstrate optical beam steering in vitro. Beam formation in brain tissue is simulated and characterized. The probes are used for optogenetic stimulation and calcium imaging.
Highlights
Encoded optogenetic actuators and fluorescence indicators have become powerful tools in the interrogation of brain activity, since they enable the control and imaging of neurons with high cell-type specificity and single-cell spatial resolution [1,2,3]
Nanophotonic waveguides with grating coupler (GC) light emitters [7,8,9,10] and micro-lightemitting-diodes [11] have been integrated onto implantable Si probes
Since light mostly scatters forward [12], low-divergence beams can be emitted from GCs over distances of 200-300 μm [7, 8]
Summary
We applied the beam propagation method (BPM) to simulate the optical scattering in tissue [S1]. The field 3 μm above the optical phased array (OPA) was calculated and used as the launch field for the above propagation simulations. The OPA field was the sum of the arrayed field profiles This process was repeated for each simulated wavelength. The same simulation model was used to study the OPA beam profiles in a non-scattering medium (water) with all phase masks set to a uniform value of 0. The arcs spanned the central lobe and the two adjacent troughs
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