In the work of Pniewski et al., the team develops a photonic crystal fiber, fabricated using a custom soft-glass, in which secondary glass is included inside the core. This high index inclusion within the core is intended to further tailor the dispersion characteristics of the fiber. And, given its small size, be of potential value for enhanced nonlinear optical functionality.
There has been significant growth in photonic crystal fibers since their invention in the 1990s and a great many geometries of varying complexity have been theoretically, computationally, and experimentally studied. Quite often, it is the structure that is different while the material from which it is made remains the same with air voids being a common secondary “phase.” In this work, the aforementioned high index inclusion, being of high lead content and quite small diameter, offers additional design flexibility in that both the geometric structure and the material properties are tailored.
One problem with materials, however, is that they do what nature tells them, which is rarely what we expect of them. And glasses, particularly multicomponent ones, are messy. Each glass component can behave differently from the others and what one starts with is frequently not what one ends with especially when the number of components is fairly large and the dimensions are small. None of this is all that surprising and the literature is full of analogous cases of optical fibers that begin as one thing compositionally and evolve into compositionally different things as the preform is made and fiber drawn.
However, in this work, the high index inclusion not only permits a tailoring of the fiber’s dispersion but also a direct route to study the diffusion of the inclusion’s glass components during fabrication. As such, the work sheds light - forgive the pun – on both the role of structure and materials on the performance of these interesting fibers.
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