A Wireless Head-mountable Device with Tapered Optical Fiber-coupled Laser Diode for Light Delivery in Deep Brain Regions

Optogenetics sets new experimental paradigms that can reveal cell type-specific contributions on the neural basis of behavior. Since most of the available systems for this purpose are based on approaches that tether animals to a set of cables, recent research activities have been focused on minimizing external factors that can alter animal movements. Current wireless optogenetic systems are based on waveguide-coupled LED and implanted 𝜇LEDs. However, each configuration separately suffers from significant limitations, such as low coupling efficiency, penetration depth and invasiveness of waveguide-coupled LED, and local heat generated by implanted 𝝁LEDs. This work presents a novel wireless head-mountable stimulating system for a wide- volume light delivery. The device couples the output of a semiconductor laser diode (LD) to a tapered optical fiber (TF) on a wireless platform. The LD-TF coupling was engineered by setting up far-field analysis, which allows a full exploitation of mode division demultiplexing properties of TFs. The output delivered light along the tapered segment is capable of stimulating structures of depths up to ~2mm. TFs are tapered to a gradual taper angle (Ψ~2° to Ψ~10°) that ends with a sharp tip (~500 nm) for smooth insertion and less invasiveness. Thus, the proposed system extends the capabilities of wireless optogenetic by offering a novel solution for wide volume light delivery in deep brain regions.