Integrated-grating-induced control of second-harmonic beams in frequency-doubling crystals

We report a novel type of integrated nonlinear photonic device for controlling the generation of several second-harmonic beams. Two-dimensional diffraction gratings are recorded with femtosecond laser pulses at the entrance surface of a frequency-doubling crystal. This periodic spatial modulation of the material surface induces noncollinear propagation of the fundamental input signal in the crystal. By slightly changing the angle of incidence of the seed beam, collinear and noncollinear phase matching can be achieved between different diffraction orders, in this way allowing the efficient generation of several second-harmonic beams.