Gel growth of 3-methyl-4-nitropyridine-1-oxide organic crystals: X-ray and nonlinear optics characterization

3-methyl-4-nitropyridine-1-oxide is an organic material presenting high optical nonlinear behavior especially for second-harmonic generation. Single crystals are obtained by spontaneous nucleation and grown by slow cooling in tetramethoxysilane gel. Coupled phase-matched second-harmonic generation and x-ray topography experiments allow one to relate nonlinear optical performance to crystalline quality.