Exact nonlinear refractive index of the GRIN rod material

Ascertain the Kerr nonlinear refractive index n2 of the specific graded-index rod material used in the experiments (commercial GRIN rods with 0.9 mm core diameter and NA 0.25 from Wavesource Photonics Inc.), through direct measurement or reliable characterization.

Background

Accurate modeling of nonlinear propagation in the GRIN rods requires the Kerr coefficient n2. The authors note that this parameter is not precisely known for the material used; they infer a rough estimate by fitting simulations to experiments.

Resolving this unknown would improve quantitative agreement between theory and experiment and enable predictive modeling across power and beam-shape variations.