Transmission characteristics of an all-optical-waveguide biomedical system for x-ray delivery

We have investigated the transmission characteristics of an alternative all-optical-waveguide system for x-ray delivery to a precise tissue area. The delivery system includes two basic optical elements: a funnel-shaped uncoated hollow glass taper and a flexible hollow delivery waveguide. The hollow taper provides direct launching of the input x-ray radiation into a delivery waveguide. It is an uncoated glass taper whose operating principle is based on the grazing-incidence effect. We investigated both experimentally and theoretically how the transmission properties of the hollow taper depend on its geometrical parameters such as cone shape, length, input and output core diameters. The x-ray-source-to-taper coupling efficiency obtained was about 20-25%. That is relatively low in comparison with typical laser-to-taper coupling efficiencies due to the poorly collimated x-ray beam. Furthermore, we have studied the x-ray beam profile conversion by the grazing-incidence-based hollow taper. The x-ray radiation was launched into the delivery waveguide by a direct taper-to-waveguide coupling. In our experiment, we used both uncoated and metal-coated hollow waveguides with various geometrical parameters. The waveguide transmission characteristics, including the coupling efficiencies and beam profile conversion, were investigated for both straight and bent delivery waveguides. The results obtained as presented in this report give considerable confidence for successful application of the all-waveguide system as an alternative x-ray delivery technique for biomedical use.