Noncollinear Maker's fringe measurements of second-order nonlinear optical layers

A novel technique for characterizing thin-film second-order nonlinearities with submicrometer resolution for the film's depth is proposed. This method is substantially a variation of the classic one-beam Maker's fringe technique and uses the second harmonic generated by two noncollinear fundamental beams. Compared with that for the one-beam case, this configuration reduces the coherence length of the process, thus increasing the resolution for the nonlinear depth measurements. The technique has been implemented on thermally poled silica samples, revealing the initial growth of the nonlinear region.