The objective of this research is to explore and harness the transverse Anderson localization as a novel guiding mechanism in disordered optical fibers. The key transformative attribute of this research is the introduction of a new guiding mechanism in optical fibers besides the conventional index-guiding and the more recent band-gap-guiding and gain-guiding mechanisms. The disordered fibers are based on the novel behavior of high- and low-refractive index regions in phase-separated glasses. The research will characterize the emergence of the localized states, as well as their linear and nonlinear guiding properties at various disorder levels.
Transverse Anderson localization was recently observed in a disordered optical waveguide, created by optical interference in a photo-refractive dielectric. Here, transverse Anderson localization will be investigated in an optical fiber medium. The fiber-based set-up is robust; the availability of well-established fiber characterization techniques enables a more detailed study of the localization phenomenon. For example, it enables direct access to the disordered refractive index profile (through SEM pictures), as well as access to the optical field. A fiber-based study is also the gateway to device-level implementation of the localization phenomenon in optical waveguides.
Optical fibers are the backbone of communication around the globe, and play a critical role in the manufacturing, defense, and health sciences industries. The fundamental understanding and mastery of novel optical fibers is vital to the national security and technological competitiveness of the United States for the development of the next generation of high-speed communication devices and lightwave-based defense applications.
Funded by this project, the research team studied optical fibers with highly disordered index profiles. They reported the first successful development of a novel disordered optical fiber in which the beam propagates using the transverse Anderson localization of light instead of the typical index-guiding mechanism. Therefore, the fiber does not have a core or cladding and can guide a beam of light coupled to any point on its input facet. The research team observed very low cross-talk and extremely low bend loss values for the simultaneous propagation of multiple spatially separated beams, indicating that this fiber will likely be suitable for short-haul spatially multiplexed optical communications. Since the start of the project, the research team has developed a complete theoretical and experimental picture of the transverse Anderson localization in disordered optical fibers. They reported the first observation of Anderson localization in a polymer and a glass optical fiber, beam multiplexing, ultra-bend performance, image transport, wave-front shaping and sharp focusing, nonlocal nonlinear behavior, and single-photon data packing. This NSF grant has resulted in several peer-reviewed journal and conference/proceeding publications, several invited talks, and a patent application. The disordered fibers that are fabricated in PI Mafiâ€™s group have been shared with several other universities. University of Wisconsin-Milwaukee (UWM, PI Mafiâ€™s former institution) and Corning Inc. have filed a joint patent application on Anderson localization in disordered fibers (Corning Inc. has licensed the patent from UWM). The most promising application of this novel fiber is in endoscopic fiber-optic imaging. The research team reported in 2014 the first demonstration of optical image transport using transverse Anderson localization of light in these fibers. The image transport quality is comparable with or better than the best commercially available multicore image fibers, with less pixelation and higher contrast. Over the next few years, Mafi's research group intends to improve the specifications of the disordered optical fiber to develop a high-resolution and robust endoscopic fiber-optic medical imaging system.