For the application in optical cochlear implants, our group develops optical modules based on a multi-channel waveguide technology, which is able to transmit light to the spiral ganglion neurons in the inner ear with high spatial resolution.
Laser diode arrays capable of emitting in the red wavelength range are used as light source to target novel red-shifted opsins which are necessary for optical excitation of the neurons. The laser diodes are used in combination with micro-sized lens systems to couple light into the facets of polymer-based waveguide arrays to facilitate multi-channel optical cochlear implants.
The waveguide arrays are designed to allow a small bending radius suitable for implantation in the inner ear by selecting polymer core and cladding materials with appropriately high index contrast. The waveguide arrays are manufactured on wafer-level using microsystem technology processes. Flexible waveguides are realized by removing a temporary carrier substrate and integrating the waveguide to optical modules.
The method of optical stray light analysis based on a top-view camera system and motorized stages allows us to analyze stray and absorption losses along the waveguide optical axis, as well as in- and outcoupling efficiencies. This information is used to incrementally improve the waveguide design, as well as minimizing cross-talk between the respective optical channels.