Soliton compression to ultra-short pulses using cascaded quadratic nonlinearities in silica photonic crystal fibers

We investigate the possibility of using poled silica photonic crystal fibers for self-defocusing soliton compression with cascaded quadratic nonlinearities. Such a configuration has promise due to the desirable possibility of reducing the group-velocity mismatch. However, this unfortunately leads to increased phase mismatch, and the dispersion is often anomalous. All this reduces the design parameter space where soliton compression is possible, and poses strong requirements on the poling efficiency. We propose to use quasi-phase matching in order to reach realistic requirements on the quadratic nonlinearity, and show that compression of nJ pulses to few-cycle duration is possible in such a fiber. A small amount of group-velocity mismatch optimizes the compression.