Determination of quadratic nonlinear optical coefficient of Al _xGa_1-xAs system by the method of reflected second harmonics

The quadratic nonlinear optical coefficient in the AlGaAs system has been systematically measured as a function of the alloy composition at the fundamental wavelength of 1.064 μm by the method of reflected harmonics. The harmonic waves from the thin-film samples are analyzed considering various interferences including multiple reflections. The experimental results show a reduction of the magnitude of the second-harmonic coefficient with increasing Al content in the AlGaAs system. This tendency is consistent with Miller's rule.