Direct numerical simulation of radiation propagation in a multicore fiber

Abstract Modern technology allows for manufacturing of multicore fibers composed of a number of microcores placed on a circle and doped with Nd 3+ ions. To understand in detail coupling between microcores and evaluate an opportunity to achieve phase-locked operation of the array, a mathematical code describing light propagation in this composed fiber was developed. A numerical code performs direct integration of scalar wave equation in paraxial approximation. The wave equation was solved using a splitting technique for diffraction/refraction processes on every propagation step. Calculations on the diffraction step were made with help of 2D FFT technique on Cartesian mesh. The problem of microcore array excitation by injection of a beam into one of them was numerically studied. Results are compared with predictions of simplified coupled-mode theory. For realizable in experiments conditions coupling coefficients are found. Evolution of far-field patterns with fiber length was studied.