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Morris S.,Center for Optical Materials Science and Engineering Technologies | Hawkins T.,Center for Optical Materials Science and Engineering Technologies | Foy P.,Center for Optical Materials Science and Engineering Technologies | Ballato J.,Center for Optical Materials Science and Engineering Technologies | And 2 more authors.
International Journal of Applied Glass Science | Year: 2012

Glass-clad optical fibers comprising a crystalline semiconductor core have garnered considerable recent attention for their potential utility as novel waveguides for applications in nonlinear optics, sensing, power delivery, and biomedicine. To date, cladding compositions have relied on commercially-available expedients and have not been tailored for the specific semiconductor core nor the application. In this work, more-optimum silicate and nonoxide glass compositions are developed for unary (Si, Ge), binary (InSb, GaAs), and ternary (GaAlSb) semiconductor cores based on two main design criteria: (1) matching the thermal expansion coefficient between semiconductor core and glass cladding and (2) matching the viscosity-temperature dependences such that the cladding glass draws into fiber at a temperature slightly above the melting point of the semiconductor. While this latter requirement is critical to the molten core fabrication method, which offers a practical approach to long fiber lengths at acceptable manufacturing speeds (>m/s), these compositions are more broadly applicable to other semiconductor fiber processing methods. Preliminary experimental results on silicon core optical fiber are provided and show a marked diminution in oxygen content relative to analogous fibers drawn using a pure silica cladding. © 2012 The American Ceramic Society and Wiley Periodicals, Inc. Source

Ballato J.,Clemson University | McMillen C.,Clemson University | Hawkins T.,Clemson University | Foy P.,Clemson University | And 4 more authors.
Optical Materials Express | Year: 2012

Described herein are glass-clad optical fibers, fabricated using a molten core fiber draw process, comprising oxide cores in the Bi2O3-GeO2 system. More specifically, the fibers utilized a borosilicate glass cladding with core compositions in the initial preform ranging from un-reacted crystalline Bi2O3-rich (Bi2O3 + GeO2) powders to stoichiometric crystalline Bi12GeO20. Fibers drawn from the as-purchased crystalline Bi2O3-rich powders were amorphous with a transmission of about 80% at 1.3 μm. Fibers drawn from the crystalline Bi12GeO20 core contained a mixture of crystalline bismuth germanate (Bi2GeO5) and bismuth oxide (δ-Bi2O3/BiO2-x). While representing an initial proof-of-concept, this work shows that commercially-relevant draw processing can be employed to yield fibers with core composition that are very difficult to fabricate using conventional methods and that the molten core method further enables in situ reactive chemistry to take place during fiberization resulting in amorphous or crystalline oxide core fibers depending on initial core composition. Perhaps more importantly is that optical fibers possessing acentric, hence optically nonlinear, oxide crystals can be realized in a scalable manufacturing manner though further optimization is required both of the core chemistry and process conditions in order to achieve a single phase and single crystalline fiber. © 2012 Optical Society of America. Source

Ballato J.,Clemson University | Hawkins T.,Clemson University | Foy P.,Clemson University | Morris S.,Clemson University | And 3 more authors.
Optics Letters | Year: 2011

Silica-clad optical fibers comprising a core of crystalline germanium were drawn using a molten core technique. With respect to previous fibers drawn using a borosilicate cladding, the present fibers exhibit negligible oxygen despite being fabricated at more than twice the melting point of the germanium. The counterintuitive result of less oxygen when the fiber is drawn at a higher temperatures is discussed. The measured propagation loss for the fiber was 0.7dB/cm at 3.39μm, which is the lowest loss reported to date. © 2011 Optical Society of America. Source

Evert A.,Clemson University | Hawkins T.,Clemson University | Stolen R.,Clemson University | Dragic P.,University of Illinois at Urbana - Champaign | And 2 more authors.
Optical Fiber Technology | Year: 2013

Reported here is a straight-forward and flexible method to fabricate silica optical fibers of circular cladding cross-section and rectilinear cores whose aspect ratio and -refractive index profile changes with position along the fiber in a deterministic way. Specifically, a modification to the process recently developed to produce longitudinally-graded optical fibers, LGFs [Opt. Express 20 (2012) 17394-17402], was employed. Herein reported are MCVD-derived germanosilicate fibers with rectangular cores where the aspect ratio changes by nearly 200% and the average -refractive index changed by about 5%. Fiber losses were measured to be about 50 dB/km. Such rectangular core fibers are useful for a variety of telecommunication and biomedical applications and the dimensional and optical chirp provides a deterministic way to control further the modal properties of the fiber. © 2013 Elsevier Inc. All rights reserved. Source

McMillen C.,Clemson University | Brambilla G.,University of Southampton | Morris S.,Clemson University | Hawkins T.,Clemson University | And 5 more authors.
Optical Materials | Year: 2012

Previously reported [Opt. Mater. 32 (2010) 862-867] was the crystallographic orientation of the core phase in a semiconductor optical fiber relative to the fiber axes. In this continuation, the same glass-clad crystalline germanium core optical fibers were tapered and, for the first time to the best of our knowledge, the influence of tapering on the core crystallography is studied and reported. Single crystal X-ray diffraction (SC-XRD) shows that the act of tapering not only modifies the fiber dimension but also re-orients the crystallography of the crystalline core. This can be especially useful to the continued optimization of these crystalline semiconductor core optical fibers and such control over crystal orientation is critical for future fiber-based nonlinear and optoelectronic devices. © 2012 Elsevier B.V. All rights reserved. Source

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