On-axis shaping of second-harmonic beams

We report complete spatial shaping (both phase and amplitude) of the second-harmonic beam generated in a nonlinear photonic crystal. Using a collinear second-order process in a nonlinear computer generated hologram imprinted on the crystal, the desired beam is generated on-axis and in the near field. This enables compact and efficient one-dimensional beam shaping in comparison to previously demonstrated off-axis Fourier holograms. We experimentally demonstrate the second-harmonic generation of high-order Hermite-Gauss, top hats and arbitrary skyline-shaped beams. A new design for photonic crystals based on non-linear computer generated holograms enables on-axis one dimensional shaping of the second harmonic beam in the near field. This method enables a compact and efficient manner of second harmonic beam shaping, and is demonstrated here for various beam shapes.