Soliton pulse compression in adiabatically tapered silicon photonic wires

We demonstrate that one can achieve compression of femtosecond optical pulse by more than a factor of three in millimetre-long dispersion engineered silicon (Si) photonic wire waveguides (SiPWWs) when the devices are operated in the soliton regime. The SiPWWs are designed such that they exhibit a negative second-order dispersion coefficient, β₂, over more than 700 nm, which allows for broadband device operation. Our computational study is based on a rigorous nonlinear propagation model, which describes the frequency dispersion up to the third order, free-carrier (FC) dispersion and FC absorption, self-phase modulation, two-photon absorption (TPA), the frequency dispersion of waveguide nonlinearity, and the FC dynamics [1,2]. Using this model we demonstrate that by choosing the parameters of the input pulse such that one operates in the soliton regime (β₂<;0) and employing adiabatically tapered SiPWWs, in order to monotonously decrease the (anomalous) dispersion coefficient, the width of femtosecond pulses can be reduced from hundreds of fs to just a few tens of fs.