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

Tapering has been demonstrated as an effective way of pushing the short-wavelength edge of a supercontinuum (SC) into the deep-blue [1–2]. The spectrum of an SC is comprised by a soliton red-edge linked to a dispersive wave (DW) blue-edge through group-velocity matching (GVM) [3]. The edges are formed when a red-shifting soliton catches up with a DW, allowing them to interact through cross-phase modulation (XPM). Tapering utilises this and allows GVM to shorter wavelength. So far the focus has been on moving the spectral edge, only little attention has been devoted to maximising the power in the blue-edge. Here we demonstrate by numerical simulations that the gradient of the taper has a major impact on the power actually available in the blue-edge.