Pulling optical fibers

Single crystal fibers have potential for a variety of optical applications both as active and passive elements. They can be produced by a variety of methods; the most versatile of which is the laser-heated pedestal growth technique. Laser heating provides a clean heat source which can be tightly focussed directly onto the sample with a beam size which is comparable with the fiber dimensions of a few μm to several mm. Contamination problems arising from crucibles and furnace components are virtually eliminated in the pedestal growth method, and the amount of material required is minimal. Very steep temperature gradients are possible which permit more rapid growth rates ( ≈ mm/min) than conventional growth methods, and can lead to increased dopant incorporation and the formation of potentially interesting metastable compounds. Crystals of both congruently and incongruently melting compounds can be grown. This method has been found to be a fast, simple, and inexpensive means to produce single crystals for property evaluation, making it an extremely valuable tool for surveying new materials. In addition, small diameter single crystal fibers will usually contain fewer defects than comparable bulk crystals.