Fourth-harmonic generation at a crystalline GaAs(001) surface.
We demonstrate fourth-harmonic generation from a GaAs(001) surface by using femtosecond pulses well below damage threshold. Our data reveal a strong fourfold anisotropic surface-specific polarization that is not present in second-harmonic generation and is nearly as strong as the bulk polarization.
Lee
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YS
Anderson
M H
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Downer
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MC