Measurement of the effective surface second harmonic susceptibility tensor in sputtered air-exposed aluminum and nickel(80)iron(20) films

In this thesis, I describe research on the fundamental origins of optical surface second harmonic generation in magnetic and non-magnetic metallic films. The work has resulted in the first measurements of all elements of the effective surface susceptibility tensor that completely describes surface second harmonic generation from a phenomenological perspective.; The first measurement was done on isotropic sputtered, air-exposed Al films. For this measurement, the complete polarization state of the second harmonic light was measured as a function of input beam polarization state and azimuthal angle of the sample. A novel technique for fitting the data was developed and the tensor elements were reduced using a realistic model for the sample linear optical constants. The results show good agreement with previous theoretical and experimental work for the biggest tensor element. However, disagreement with theoretical predictions is found for the other two families of elements, where the measured values are two orders of magnitude smaller than what is predicted by theory.; The second measurement was done on sputtered, air-exposed Ni₈₀Fe ₂₀ films. Because these films are structurally isotropic but magnetically anisotropic, the symmetry of the system is reduced and the susceptibility tensor is more complicated. For these films, the second harmonic intensity and polarization state was measured as a function of input polarization angle, sample azimuthal angle, and sample in-plane magnetization direction. The data was fitted using measured linear optical constants to a model that includes both magnetic and non-magnetic tensor elements. The results have uncovered a previously unrecognized mirror symmetry of this system. Further, I find that the magnetic tensor elements are nearly equal in size to the non-magnetic tensor elements, in strong contrast to the linear magneto-optic Kerr effect, where the off-diagonal magnetization-sensitive elements of the linear susceptibility are less than 1% the size of the non-magnetic on-diagonal elements. Together with the results for the isotropic non-magnetic system, these results suggest that the large magnetization-sensitivity of optical surface second harmonic generation may be correlated to the suppression of the non-magnetic tensor elements.; Finally, this thesis describes earlier work done to compare surface and bulk magnetization in Ni₈₀Fe₂₀ films using surface second harmonic generation simultaneously with the linear magneto-optic Kerr effect. These results show that the magnetization responds essentially identically in the surface and bulk of these systems.