Characterization of microstructures of specialty optical fibers for electric field sensing by propagation-based X-ray phase-contract tomography

Abstract

In this work, we present a quantitative (statistical) 3D morphological characterization of optical fibers used in electric field sensing. The characterization technique employs propagation-based X-ray phase-contrast microcomputed tomography (micro-CT). Particularly, we investigate specialty optical fibers that contain microstructured holes that are electrooptically modified by thermal poling to induce second-order nonlinear effects (SONE). The efficiency of SONE is reflected in the characterization parameter Vπ, which is highly dependent on the dimensions of the fiber. The fiber microstructures must be uniform to allow the fabrication of reproducible devices. The results obtained using the micro-CT technique showed that an uncertainty of ±1.7% arises in the determination of the expected value of the voltage that causes a change in the phase of the electromagnetic wave equal to π rad (Vπ), showing a great advantage when it is compared with other techniques e.g. SEM, which would need at least 1000 images of the cross-section of the optical fiber taken in different points making the process more expensive and time consuming.