Square-core jacketed air-clad fiber produces uniform field

Square glass rods have always been one of the best ways to create a uniform field of light from a laser beam (except for laser-speckle effects); such a field can be useful for materials-processing applications.

Dec 1st, 2006
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Square glass rods have always been one of the best ways to create a uniform field of light from a laser beam (except for laser-speckle effects); such a field can be useful for materials-processing applications. An optical fiber with a square core can serve this purpose and transmit optical power over long distances too. Researchers at the University of Southampton (Southampton, England) have developed a jacketed microstructured air-clad fiber that creates a uniform field and, because it is made entirely from pure silica, is straightforward to fabricate and very transmissive.

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The fiber preform consists of a square array of circular rods with smaller rods in the interstices, surrounded by thin-walled capillaries and contained within a jacket tube. Pressurizing some of the capillaries while drawing the fiber results in a 380 μm solid square core surrounded by a border of air holes 20 μm wide with 2 μm glass webs between them, and a solid jacket. When filled with, for example (from left to right), single-mode 633 nm light, single-mode 1060 nm light, or multimode 915 nm light, the fiber core produces a uniform field. Contact John Hayes at jrh@orc.soton.ac.uk.

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