Infrared supercontinuum frequency doubling via nonlinear Raman-Nath and Cerenkov scattering processes

We consider experimentally the frequency doubling of a near infrared supercontinuum light in a periodically poled lithium niobate crystal. The supercontinuum light was generated by a photonic crystal fiber and then filtered by an infrared passband filter, in order to obtain a spectrum from 1100 nm to 1500 nm. Once that spectrum was injected in the crystal, we observed a broadband frequency conversion towards the visible domain between 560 nm and 700 nm. Our goal is to demonstrate the capability of the spatio-temporal quadratic unidirectional pulse propagation model, providing insight into the complex experimental observations. We enlighten the role of Cerenkov second-harmonic emission, nonlinear Raman-Nath and nonlinear Bragg scattering processes in the broadband frequency conversion from infrared to visible light.