Taper designs for semiconductor filled fibres

Recently there has been much interest in designing optical tapers for nonlinear pulse manipulation in both standard and semiconductor filled fibres. Such tapers can be used to overcome the large linear losses in semiconductor filled fibres while allowing parabolic pulse generation or soliton propagation for example. However once the taper profile has been chosen to overcome the linear loss problem in semiconductor filled fibres the problem of two photon absorption (TPA) and associated free carrier effects remain. This work shows that it is possible to use a genetic algorithm to design tapers that alleviate both linear and nonlinear losses and hence should allow high quality pulse propagation over several centimetres of semiconductor filled fibres.