Surface relief diffraction gratings written on β-BaB2O4 crystal by femtosecond pulses

Surface relief diffraction gratings were written at the entrance surface of a β-BaB2O4 (BBO) crystal under irradiation with femtosecond laser pulses. Probe–beam diffraction and atomic force microscopy (AFM) were employed to characterize the diffraction properties and the microstructures of the gratings. The maximal first-order diffraction efficiency of these gratings is approximately 63%. The surface periodic structure of the material induces noncollinear propagation of the fundamental input beam in the crystal. Using this diffractive optical element, efficient generation of multiple second-harmonic beams was achieved.