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We report simultaneous measurements and ab initio calculations of the second-order nonlinear coefficients for SiC polytypes. Our measured values for χzzz (χzxx) are 18 (−4) pm/V for 4H SiC and 24 (−4) pm/V for 6H SiC. They are in good agreement with our theoretical results.

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Multiphoton reduction of Eu 3+ to Eu 2+ in methanol was induced by irradiation with the second harmonic (394 nm, 2 ps) of a Ti:sapphire laser. The conversion efficiencies were increased to 0.3 for short pulse excitation, as compared to on the order of 10 -5 for a nanosecond dye laser pulse. It appears that a three-photon process pumps a deep charge-transfer state from which Eu 3+ efficiently dissociates to Eu 2+ . On the basis of the excitation spectra, the first intermediate state is the 5 L 6 state, which is one of the f-electronic excited states. The Eu 2+ concentration increased shot by shot and approached a plateau. The saturation behavior will be explained in terms of the back photooxidation of Eu 2+ to Eu 3+ .