Abstract

A recent semiclassical theory of two-photon multiwave mixing¹ allows one to examine such diverse areas as saturation spectroscopy, phase conjugation,² and two-photon Doppler-free spectroscopy.³ The theory is based on the two-photon two-level scheme with upper level a and lower level b and no dipole matrix element connecting them. The pump field frequency v₂ is approximately one-half of the frequency difference ω = ω_a – ω_b. Transitions occur between levels a and b via nonresonant intermediate levels, which are assumed to acquire no appreciable population. The medium is probed by a nonsaturating field at frequency v₁.

© 1986 Optical Society of America