Second harmonic generation in hexagonal silicon carbide

We report optical second harmonic generation measurements in single crystal αâ€�SiC of polytype 6H. The angular dependence of second harmonic intensity was consistent with two independent nonvanishing second order susceptibility components, as expected for a crystal with hexagonal symmetry. For the fundamental wavelength of 1.064 μm the magnitudes of the two components were determined to be χ_zzz ⁽²⁾=±1.2×10^−7 and χ_zxx ⁽²⁾=∓1.2×10^−8 esu. The corresponding linear electroâ€�optic coefficient computed from this value is r_zzz=±100 pm/V. The wavelength dependence of the nonlinear susceptibility was examined for second harmonic wavelengths between the bandgap (400 nm) and the red (700 nm), and was found to be relatively uniform over this region. The refractory nature of this compound and its large nonlinear optical coefficients make it an attractive candidate for high power nonlinear optical waveguide applications.