Linear and nonlinear optical properties of KDP crystals with incorporated Al2O3⋅nH2O nanoparticles

•KDP single crystals with incorporated Al2O3·nH2O nanoparticles were grown.•An absorption band caused by the presence of NOA in the crystals is revealed.•The sign inversion of the refractive nonlinear optical response in KDP:NOA crystals was observed.

Optical and nonlinear optical properties of a novel composite system based on KDP single crystals with embedded nanoparticles of nanostructured oxyhydroxide of aluminum (Al2O3·nH2O, NOA), were studied. KDP crystals with NOA nanoparticles (KDP:NOA) possess high optical quality and homogeneity. Optical spectroscopy showed the presence of an absorption band at 270 nm caused by NOA nanoparticles incorporated in the KDP matrix. There was observed an enhancement of nonlinear refractive index and inversion of its sign in KDP:NOA crystals in comparison with nominally pure KDP crystals under excitation of picosecond laser pulses. The obtained results demonstrate that KDP:NOA is a promising composite material for optoelectronics and nonlinear optics.