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 LEDs. 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 the full exploitation of the 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 (2° to 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.