Group-acceleration matching in tapered optical fibers for maximising the power in the blue-edge of a supercontinuum

In this paper, we demonstrate by numerical simulations that the gradient of the taper has a major impact on the power actually available in the blue-edge.To investigate the influence of GAM, we simulated the propagation of a 10 fs fundamental soliton through asymmetrically tapered fibers with varying gradients. The initial 2 m of uniform fiber ensures that the soliton has fully caught-up and established GVM with the DW before entering the taper. The tapered section is always 4 m, but with varying up and down-tapering lengths. The energy of the DW at the end of the fiber. The tendency is clear: a smaller taper gradient allows the soliton to blue-shift more of the energy in its DW. In other words, when the GAM is low (small taper gradient/long taper), the GVs of the soliton and DW change at similar rate, which gives a longer XPM interaction length and allows the soliton to blue-shift more of the energy in its DW. These observations explain the previously observed lack of power in the blue-edge in, and are very important for SC generation in tapers aimed at moving the blue-edge further down in the deep-blue.