Harrington The overall objective of the proposed work is to develop the hollow waveguide technology necessary to fabricate low-loss, coherent image bundles for broadband infrared imaging. The approach to be taken is to fabricate hollow-glass, coherent bundles which then can be coated for broadband infrared transmission. The image bundles will be fabricated using both mandrel wrap and leach bundle technologies. The advantage of using hollow oxide glass tubing to form the bundles is that conventional coherent bundling methods used for solid-core glass fibers can be used here. Once the coherent hollow guide bundles have been made, the inside walls of the glass tubing will be coated using two technologies developed at Rutgers University. The first is liquid-phase chemistry and the second is chemical vapor deposition (CVD). These methods have proven very successful in making single waveguides with losses as low as 0.1 dB/m and lengths up to 13 m. The challenge in this program is to extend the current technology used to coat single hollow guides with bore sizes as small as 250 um to the approximately 5O-~m-bore size guides which will make up the IR image bundle.
The significance of this research lies in the anticipated reduction in loss for hollow glass guides by a factor of 10 or more through the deposition of multilayer dielectric coatings. The development of an efficient, coherent IR bundle for imaging beyond 2 ~m would mark the first time that such a high resolution, broadband bundle has been fabricated and, it is believed, this technology will have a major impact on thermal imaging systems used for recognition and process control. If we are successful in reducing the loss of the hollow guides by a factor of ten over current losses we will not only have a fiber well suited for thermal imaging but also a waveguide with significant potential in delivering laser power for surgical and other medical applications. In addition, our hollow bundle could be used in a transmit mode as well as in the receive mode. That is, it is possible to transniit laser energy for local heating and then to interrogate the resulting thermal energy via the same fiber bundle. Finally, it should be possible to make the ultimate smart fiber optic involving thermal imaging, power delivery, and chemical sensing all via the same hollow guide bundle. ***
