Efficient broadband frequency conversion via simultaneous adiabatic three wave mixing processes

Two frequency-cascaded and spatially simultaneous three-wave-mixing processes, each pumped by a different frequency, are studied in a quasi-phase-matching crystal with chirped poling. Theory, numerical simulation, and experiment all show that efficient two-process adiabatic frequency conversion takes place over a broad range of input wavelengths. Experimentally, up to five process cascades are obtained. Furthermore, it is demonstrated that reversing the chirp sign results in a different conversion for the same input wavelength. This method can be applied to generation of an all-optically tunable frequency comb.