Broadband Response of Second Harmonic Generation in a Two-Dimensional Quasi-Random Quasi-Phase-Matching Structure

The broadband response of second harmonic generation (SHG) is experimentally observed in a two-dimensional (2D) quasi-random quasi-phase-matching (QPM) structure. A nonlinear conversion efficiency of more than 50% is obtained. Due to the line-type distribution of the reciprocal vector, the second harmonic wave (SHW) covering a broad frequency band is efficiently radiated in the shape of one single spot or three spots instead of a stripe. This is believed to be favorable for its practical application and paves the way for the use of ultrahigh-bandwidth light sources and devices in modern optical technologies.