Numerical investigation of the nonlinear spectral broadening aiming at a few-cycle regime for 10 ps level Nd-doped lasers

We present a cascaded nonlinear spectral broadening scheme for Nd-doped lasers,featuring with long pulse duration and high average power.This scheme is based on two multi-pass cells(MPCs)and one multiple-plate supercontinuum generation(MPSG),and the numerical investigation is driven by a home-made Nd-doped fiber laser with 12 ps pulse duration,50 kHz repetition rate and 100 W average power.The MPC-based first two stages allow us to broaden the pulse spectrum to 4 nm and 43 nm respectively,and subsequently,the MPSG-based third stage allows us to reach 235 nm spectral bandwidth.This broadened spectrum can support a Fourier-transfer-limited pulse duration of 9.8 fs,which is shorter than three optical cycles.To the best of our knowledge,it is the first time to demonstrate the possibility of few-cycle pulses generation based on the 10 ps level Nd-doped lasers.Such few-cycle and high average power laser sources should be attractive and prospective,benefiting from the characteristics of structure compact,low-cost and flexibility.