The fabrication parameters necessary for the development of waveguides that transmit energy from deep ultraviolet to infrared range on wide band gap semiconductor thin film is discussed. Such waveguides in conjunction with microfluidic systems may be used for a spatial and temporal drug delivery in neural tissue. These waveguides may also be suitably modified and employed for novel applications like lab-on-a-chip technologies for Raman Spectroscopy and high speed telecommunication optical switches. Highly textured AlN thin films are grown on C-plane sapphire with high refractive index buffer layer by plasma source molecular beam epitaxy (PSMBE). Analytical measurements such as atomic force microscopy (AFM), ultraviolet spectroscopy and X-ray diffraction, were used to characterize surface morphology and crystalline structure of these films. The fabrication of waveguide structures was performed using laser micromachining with a KrF Excimer laser of wavelength 248 nm and pulse duration of 25ns. Waveguide etching rate for the AlN thin films is investigated as a function laser pulse energy and number of pulses. It is found that etching rate increases almost linearly with both--the pulse energy and number of pulses.
We have developed a microfluidic retinal prosthesis, using wide bandgap optical wavelength semiconductor thin film waveguides, to facilitate spatial and quantitative photactivation of “caged” neurotransmitter to microfluidic channels. Novel waveguide materials and micromachining technology are necessary to fabricate 360 nanometer capable waveguides for the microfluidic device. Single crystal wide bandgap semiconductor thin films are grown on sapphire by plasma source molecular beam epitaxy (PSMBE). 248 nanometer KrF Excimer laser micromachining technology is employed to micro-fabricate wave-guiding channels and microfluidic structures. A waveguide that allows for spatial and temporal drug delivery within the retina was fabricated. In addition, there is a need for a waveguide structure that may be used in physiological drug delivery systems. A device that may deliver ultraviolet light in precise intensities and to selective areas of a microfluidic implant without direct ultraviolet exposure to the biological cells is needed in retinal and cortical implants. Results of a prototype microfluidic waveguide system will be presented.