SBIR Phase I: Feasibility of Chiral Fiber Polarizer

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This Small Business Innovation Research (SBIR) Phase I project is to demonstrate the feasibility of a new class of in-fiber polarizers and polarization converters based upon chiral optical fibers. Helical birefringence is imparted to these optical waveguides by twisting fibers with noncircular cores as they pass through a miniature oven. Thus thesechiral fiber gratings (CFGs) do not require coherent irradiation of photosensitive glass, which is used to process fiber Bragg gratings (FBGs), but rather are created in a versatile continuous process from specially prepared glass preforms. They are true fiber devices and do not require any substrates, bulk components, or rigid package. Both the polarizer and polarization converter will be based on CFGs with a pitch of tens of microns. These CFG-based devices, which will be fabricated at dramatically reduced cost, will permit the control of the polarization of transmitted light with high extinction ratio over broad or narrow spectral ranges as dictated by the application. They will have broad application in telecommunications to polarization mode dispersion (PMD) compensation, wavelength- division multiplexing (WDM), and Faraday rotators. Polarizers are also key to sensors relying on optical interference such as gyroscopes.Polarization and frequency selective chiral fibers have applications ranging from telecommunications to sensing. The use of external modulators for high bandwidth fiber telecommunication requires that the incident wave be linearly polarized. This necessitates use of a polarizer since laser sources used in telecommunications generally have random polarization. Further any use of polarization maintaining fiber requires that polarized light be launched into the fiber. Polarizers are also key components in PMD compensation systems. The versatile chiral polarizers may be fabricated from refractory or radiation resistive glasses so that they may function in harsh environments with high levels of radiation, high temperature, or corrosive chemicals.