Abstract

Consider sum frequency generation (SFG) ω₃ = 2 ω₁ + ω₂ in a phase matched metal-noble gas mixture, using two lasers ω₁ and ω₂, where 2 ω₁ is tuned to a two photon transition Ω_g2 and ω₂ is shifted across Rydberg transitions Ω_2n (g groundstate, 2 excited state, n Rydberg state of the metal atom). Then the intensity of the SFG spectrum I₃ (ω₃)~ |χ⁽³⁾ (ω₃)|² displays resonances and related antiresonances, separated by (1) which are caused respectively by constructive and destructive interference of resonant and nonresonant parts of the 3. order nonlinear susceptibility χ⁽³⁾ (ω₃ ≃ Ω_ng) = χ^R(ω₃)+ χ^NR (3) The products μ_2nμ_ng:= x_n of the dipole transition matrix elements may then be obtained from a simple measurement of the frequency spacings Δω_n at a large number of transitions Ω_gn and solving iteratively the coupled equation system (1),(3); neither absolute radiation intensity nor vapour density deter mination is needed.

© 1984 Optical Society of America