Nonlinear optical mixing of existing laser frequencies to access portions of the spectrum where lasing action is not easily obtainable is common practice today. Although nonlinear solid-state media are available [1] for frequency conversion from just under 200 nm in the ultraviolet to about a few microns in the infrared, the generation of widely-tunable laser radiation in the mid-to-far infrared and VUV regions typically requires four-frequency mixing in atomic vapors. In the past, frequency conversion in atomic vapors suffered from poor conversion efficiencies due to the small magnitude of the third-order nonlinear susceptibility and the difficulty in phasematching. We demonstrate a method [2] for performing four-frequency mixing which overcomes both of these shortcomings, allowing efficient frequency conversion with moderate pump intensities.Nonlinear optical mixing of existing laser frequencies to access portions of the spectrum where lasing action is not easily obtainable is common practice today. Although nonlinear solid-state media are available [1] for frequency conversion from just under 200 nm in the ultraviolet to about a few microns in the infrared, the generation of widely-tunable laser radiation in the mid-to-far infrared and VUV regions typically requires four-frequency mixing in atomic vapors. In the past, frequency conversion in atomic vapors suffered from poor conversion efficiencies due to the small magnitude of the third-order nonlinear susceptibility and the difficulty in phasematching. We demonstrate a method [2] for performing four-frequency mixing which overcomes both of these shortcomings, allowing efficient frequency conversion with moderate pump intensities.

Nonlinear OpticsJan 1, 19960 citations

Distinction of the competing processes in nonlinear resonant frequency mixing in atoms

Valentin Mitev, Lubomir I. Pavlov, K. V. Stamenov +1 more

Optical and Quantum ElectronicsJan 1, 19800 citations

Theory of Optical Frequency Mixing Using Resonant Phenomena

Ali Javan, A. Szöke

The nonlinear interaction of two intense optical waves with three energy levels of an atomic system is analyzed theoretically. The frequencies of the applied fields are assumed to be on or near two of the resonances involving the three levels. Particular attention is given to the generation of power at the difference frequency of the two applied fields where their frequency separation lies in the far-infrared range of the spectrum. In the limit of large input fields where atomic transitions are driven to saturation, the generated difference-frequency power is no longer proportional to the product of the two input powers. It is shown that, in this limit, the total rate of emission of photons at the difference frequency may, in principle, approach a value given by $\frac{\mathrm{rN}}{T}$ , where $N$ is the total number of atoms, $T$ is the average time of coherent interaction of atoms and the radiation field, and $r$ is a factor which in favorable cases approaches unity at low temperatures. Also, a number of additional effects are encountered due to coherent double-quantum transitions among various levels which may be ignored only for weak input powers. These effects are highly dependent on the modes of relaxations of atomic levels and the details of the line shape. The results are applied to several cases, in which the resonance condition yields large efficiency in nonlinear frequency mixing.The nonlinear interaction of two intense optical waves with three energy levels of an atomic system is analyzed theoretically. The frequencies of the applied fields are assumed to be on or near two of the resonances involving the three levels. Particular attention is given to the generation of power at the difference frequency of the two applied fields where their frequency separation lies in the far-infrared range of the spectrum. In the limit of large input fields where atomic transitions are driven to saturation, the generated difference-frequency power is no longer proportional to the product of the two input powers. It is shown that, in this limit, the total rate of emission of photons at the difference frequency may, in principle, approach a value given by $\frac{\mathrm{rN}}{T}$, where $N$ is the total number of atoms, $T$ is the average time of coherent interaction of atoms and the radiation field, and $r$ is a factor which in favorable cases approaches unity at low temperatures. Also, a number of additional effects are encountered due to coherent double-quantum transitions among various levels which may be ignored only for weak input powers. These effects are highly dependent on the modes of relaxations of atomic levels and the details of the line shape. The results are applied to several cases, in which the resonance condition yields large efficiency in nonlinear frequency mixing.

Physical ReviewJan 18, 196515 citations

Multiwave coherent interaction and nonlinear frequency shift

Alexander A. Zabolotskii

Journal of Experimental and Theoretical PhysicsNov 1, 19882 citations

\frac{\mathrm{rN}}{T}

, where

N

is the total number of atoms,

T

is the average time of coherent interaction of atoms and the radiation field, and

r

is a factor which in favorable cases approaches unity at low temperatures. Also, a number of additional effects are encountered due to coherent double-quantum transitions among various levels which may be ignored only for weak input powers. These effects are highly dependent on the modes of relaxations of atomic levels and the details of the line shape. The results are applied to several cases, in which the resonance condition yields large efficiency in nonlinear frequency mixing.