Four-photon-resonant third-harmonic generation in Hg.
A tunable resonant enhancement of third-harmonic and sum-frequency generation is observed at four-photon resonance with the 7(1)S, 6(1)D, and 6(3)D levels and at five-photon resonance with 9(1)P levels of atomic mercury. The causes of this resonant enhancement are examined and appear to include a nonlinear refractive index and nonlinear mixing of order 5 and higher. A perturbative treatment of the nonlinearities is found to be inadequate.
Smith
A V
AV
Sandia National Laboratories, Albuquerque, New Mexico 87115, USA.