Four wave mixing at the band edge of a 1D photonic crystal

One way to realize such a light localization is to structure the material at the wavelength size level creating thus a photonic crystal that may present a photonic band gap that prevents propagation of light in it for a given frequency bandwidth. Near its band edge such a structure becomes transparent and presents a low group velocity connected to a very pronounced light localization inside the structure or, equivalently, a high local intensity that favors the nonlinear phenomena. To study such an effect we develop a four wave mixing experiment based on a tunable picosecond laser source that allows to perform a spectroscopic study of the phase conjugate reflectivity