AIR FORCE INSTITUTE OF TECHNOLOGY WRIGHT-PATTERSON AFB OH WRIGHT-PATTERSON AFB United States
This thesis conducts research involving designing, fabricating, and testing optical fiber tip refractive index sensors. The fabrication process used for these sensors is a two-photon polymerization process utilizing a photo sensitive polymer. Unlike planar lithography, this fabrication process allows the creation of arbitrary shapes with a great degree of freedom. There is a total of three different designed fiber tip sensors that are all fabricated and tested. One is a flat surfaced single cavity Fabry-Prot interferometer FPI device, another is a flat surfaced double cavity FPI device, and the last is a confocal surfaced double cavity FPI device. These sensors are tested for both thermal radiation and volatile organic compounds VOC sensing. Thermal radiation sensing involves exposing the device to temperatures ranging from room temperature up to 120 deg C. As the temperature increases the fiber tip structure expands which changes its reflection spectrum. Each device was also exposed to isopropanol in gaseous form which results in a refractive index change. This change is also observed in the reflection spectrum. Lastly, research was conducted on thin dielectric reflective coatings for the purpose of increasing the reflectivity of the device surfaces resulting in a higher quality factor.