Third-Harmonic Generation in Absorbing Media of Cubic or Isotropic Symmetry

TLDR

The study compares third‑harmonic susceptibility data with infrared frequency‑mixing measurements and determines the cubic anisotropy of χ^(3)(3ω) in silicon and alkali halide crystals using circularly polarized pulses. Third‑harmonic generation was measured in strongly absorbing media by reflection using a picosecond Nd‑glass laser, yielding χ^(3)(3ω) values for diamond, Si, Ge, GaAs, Be, Mg, Al, Cu, Ag, and Au relative to LiF, revealing distinct valence‑ and conduction‑band dispersion and confirming selection rules for circularly polarized third‑harmonic generation in both transparent and absorbing media.

Abstract

Third-harmonic generation in strongly absorbing media has been measured in reflection, by means of a picosecond pulse train from a mode-locked Nd-glass laser. The nonlinear susceptibility ${\ensuremath{\chi}}^{(3)}(3\ensuremath{\omega})$ has been measured in the semiconductors diamond, Si, Ge, and GaAs, and the metals Be, Mg, Al, Cu, Ag, and Au relative to LiF. The data are compared with data for ${\ensuremath{\chi}}^{(3)}$ obtained in the infrared from frequency mixing with C${\mathrm{O}}_{2}$ lasers. The different dispersion characteristics for valence- and conduction-band contributions are pointed out. The cubic anisotropy of ${\ensuremath{\chi}}^{(3)}(3\ensuremath{\omega})$ in silicon and several alkali halide crystals is determined by means of circularly polarized laser pulses. The selection rules for the generation of circularly polarized third harmonics have been confirmed both in transparent and in absorbing media.