Abstract

Recent findings indicated that the reduction of topological fluctuation in silica glass occurs by applying hot-compression (HC).^1,2 The suppression mechanism (called topological pruning) decreases the optical loss,³ thereby posing great significance in the optimization of glass in optical communication fibers. Fig. 1(a) shows the refractive index n of HC silica glass increasing linearly with pressure. The tendency is reasonable considering pressure densifies the averaged structure of glass. However, as shown in Fig. 1(b), the Abbe number, v, increases with pressure, indicating the dispersion of the optical oscillator strength sharpened.⁴ To determine the details of this topological fluctuation change, total structure factors, S(q) are deduced from the high-energy X-ray diffraction (HEXRD) data as shown in Fig. 2. Pressure induced sharpening of FSDP (First Sharp Diffraction Peak) was observed, indicating the intermediate-range ordering grows by pressure. Along with the sharpening, longer-distance ordering, denoted as SP in Fig.2, disappeared. Using molecular dynamics (MD) simulation-reverse Monte Carlo (RMC) modeling, the growth and disappearance of those specific ordering are explained as the disappearance of voids which behaves as optical scattering particles.¹ This talk will explain in further details this investigation into the role of topological fluctuations in the optical performance of silica glass.²

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