"A Dynamical Model of Harmonic Generation in Centrosymmetric Semiconductors"
Charles M. Bowden Research Center AMSRD-AMR-WSS, RDECOM, Redstone Arsenal, Alabama 35898-5000, USA
Abstract: We study second and third harmonic generation in centrosymmetric materials at visible and UV wavelengths in bulk and cavity environments. Second harmonic generation is due mostly to a combination of symmetry breaking, the magnetic portion of the Lorentz force, and quadrupolar contributions that impart peculiar features to the angular dependence of the generated signals, in analogy to what occurs in metals. The material is assumed to have a non-zero third order nonlinearity that gives rise to most of the third harmonic signal. Using the parameters of bulk Silicon we predict that cavity environments can significantly modify reflected and transmitted second (390nm) and third (260nm) harmonic generation, with dramatic improvements for third harmonic generation, notwithstanding the fact that the harmonic field may be tuned to a wavelength range where the dielectric function of the material is negative. A phase locking mechanism binds the pump to the generated harmonics and inhibits absorption at the harmonic wavelengths. These results highlight additional flexibility and usefulness of materials like Silicon as a nonlinear medium in the visible and UV ranges.