Modeling of Mechanisms for the Creation of an Internal Clad in Sapphire Optical Fiber Using the ~6Li(n,α)~3H Reaction

摘要

The focus of this work is to model the creation of a cladding, which is internal to a sapphire optical fiber, by irradiating asapphire fiber, that is surrounded by an annulus of Li-6 enriched lithium carbonate powder, in a nuclear reactor. Such afiber has been created using the Ohio State University Research Reactor. The ~6Li(n,α)~3H reaction creates high energytritons and alpha particles that irradiate the fiber simultaneously to a depth of 24 microns, along the entire periphery of thesapphire fiber. The irradiation slightly reduces the index of refraction in the fiber’s periphery, thus creating a refractivecladding within the fiber. The Monte Carlo radiation transport code MCNP was used in combination with SRIM/TRIM topredict the modification of the fiber that results from the irradiation. Our analysis predicts that whether it is displacementdamage or the density of implanted ions that is responsible for the modification of η, or a combination of both, theirradiation yields a graded index in the fiber, with η decreasing monotonically from the value of the native sapphire 24micrometers from the surface of the fiber to a minimum value at the surface of the fiber.