Nonlinear optical frequency conversion by cascaded difference frequency generation

We propose a nonlinear optical frequency conversion method based on cascaded difference frequency generation. Feasible designs are presented that enable the cascaded optical waves. They are initially generated by cascaded difference frequency generation with two pump waves, then transferred to high-order Stokes waves by optimized cascaded difference frequency generation, and finally congregated at a few spectral lines. We demonstrate wide frequency tuning characteristics and high conversion efficiency characteristics of the nonlinear frequency convertor by providing a theoretical framework. The frequency tuning from 291 THz to 175 THz and energy conversion efficiency exceeding 30% are achieved by numerical calculations. The nonlinear frequency convertor exhibits physics distinctly different from conventional three-wave mixing parametric amplification or difference frequency generation. We argue that the nonlinear frequency convertor based on cascaded difference frequency generation is promising for achieving efficient and robust frequency conversion.