We have investigated degenerate four-wave mixing (DFWM) in a strongly absorbing molecular gas. A theory taking into account saturable absorption of the interacting beams is used to explain the dependence of the DFWM reflectivity on laser intensity and on the molecular number density. These parameters have a great influence on the observed spectra, owing to linear absorption that suppresses the DFWM signal in the line center of the molecular transitions. The great sensitivity of the spectra to the experimental conditions limits the applicability of DFWM for spectroscopic studies in absorbing media.We have investigated degenerate four-wave mixing (DFWM) in a strongly absorbing molecular gas. A theory taking into account saturable absorption of the interacting beams is used to explain the dependence of the DFWM reflectivity on laser intensity and on the molecular number density. These parameters have a great influence on the observed spectra, owing to linear absorption that suppresses the DFWM signal in the line center of the molecular transitions. The great sensitivity of the spectra to the experimental conditions limits the applicability of DFWM for spectroscopic studies in absorbing media.

Journal of the Optical Society of America BDec 1, 19926 citations

EXPERIMENTAL AND THEORETICAL STUDIES OF DEGENERATE FOUR-WAVE MIXING I. IODINE

S. K. Lin, Chung-Jen Wu, Chung‐Hung Chang +3 more

We have investigated the dependence of degenerate four-wave mixing (DFWM) spectra of gas-phase $I_{2}$ on laser intensity, molecular transition moments and molecular concentration. The experimental results are interpreted by using a weak-field theory of DFWM derived with a density-matrix method. For comparison, the direct absorption spectra of $I_{2}$ are also presented. We have demonstrated, in our observed DFWM spectra of $I_{2}$ , that the spectral resolution in DFWM can be better than that of linear optical spectroscopy. The outcome has also been elucidated by the theoretical result.We have investigated the dependence of degenerate four-wave mixing (DFWM) spectra of gas-phase $I_{2}$ on laser intensity, molecular transition moments and molecular concentration. The experimental results are interpreted by using a weak-field theory of DFWM derived with a density-matrix method. For comparison, the direct absorption spectra of $I_{2}$ are also presented. We have demonstrated, in our observed DFWM spectra of $I_{2}$, that the spectral resolution in DFWM can be better than that of linear optical spectroscopy. The outcome has also been elucidated by the theoretical result.

Jan 1, 19950 citations

Power dependence of transient degenerate four-wave mixing in molecular systems

A. V. Pakhomov, Chung-Jen Wu, Yit‐Tsong Chen +1 more

The object of this study is to quantitatively elucidate the laser-power dependence in transient degenerate four-wave mixing (DFWM) with an emphasis on the high laser-pump intensity region. We discuss our investigation on the power dependence of transient DFWM by taking gas-phase iodine ( ${\mathrm{I}}_{2}$ ) molecules as a testing example. The distinct physical feature is that in the high-power laser pump, where both laser-pulse duration and the inverse of pump rate are much shorter than the molecular population relaxation time, the steady-state DFWM theory of Abrams and Lind [Optical Phase Conjugation, edited by R. A. Fisher (Academic, New York, 1983), Chap. 8, pp. 211--284; Opt. Lett. 2, 94 (1978); 3, 205 (1978)] is not appropriate. The prediction by the steady-state theory has shown the DFWM to decrease with increasing laser-pump intensity as a function of 1/ ${\mathrm{I}}_{\mathrm{laser}}$ , which disagrees with the saturation behavior observed in the experiment. To elucidate the dependence of DFWM on the laser pump intensity, a non-steady-state extension of the nonperturbative theory of Abrams and Lind is required. The non-steady-state theoretical result will be shown to be in good agreement with the experimental power dependence at resonance transient DFWM especially in the high-power pump region.The object of this study is to quantitatively elucidate the laser-power dependence in transient degenerate four-wave mixing (DFWM) with an emphasis on the high laser-pump intensity region. We discuss our investigation on the power dependence of transient DFWM by taking gas-phase iodine (${\mathrm{I}}_{2}$) molecules as a testing example. The distinct physical feature is that in the high-power laser pump, where both laser-pulse duration and the inverse of pump rate are much shorter than the molecular population relaxation time, the steady-state DFWM theory of Abrams and Lind [Optical Phase Conjugation, edited by R. A. Fisher (Academic, New York, 1983), Chap. 8, pp. 211--284; Opt. Lett. 2, 94 (1978); 3, 205 (1978)] is not appropriate. The prediction by the steady-state theory has shown the DFWM to decrease with increasing laser-pump intensity as a function of 1/${\mathrm{I}}_{\mathrm{laser}}$, which disagrees with the saturation behavior observed in the experiment. To elucidate the dependence of DFWM on the laser pump intensity, a non-steady-state extension of the nonperturbative theory of Abrams and Lind is required. The non-steady-state theoretical result will be shown to be in good agreement with the experimental power dependence at resonance transient DFWM especially in the high-power pump region.

Physical Review AApr 1, 19971 citation

Theory of degenerate four-wave mixing in three-level atoms

M. Pinard, B. Kleinmann, G. Grynberg

Optics CommunicationsSep 1, 198414 citations

We have investigated the dependence of degenerate four-wave mixing (DFWM) spectra of gas-phase

I_{2}

on laser intensity, molecular transition moments and molecular concentration. The experimental results are interpreted by using a weak-field theory of DFWM derived with a density-matrix method. For comparison, the direct absorption spectra of

I_{2}

are also presented. We have demonstrated, in our observed DFWM spectra of

I_{2}

, that the spectral resolution in DFWM can be better than that of linear optical spectroscopy. The outcome has also been elucidated by the theoretical result.

{\mathrm{I}}_{2}

) molecules as a testing example. The distinct physical feature is that in the high-power laser pump, where both laser-pulse duration and the inverse of pump rate are much shorter than the molecular population relaxation time, the steady-state DFWM theory of Abrams and Lind [Optical Phase Conjugation, edited by R. A. Fisher (Academic, New York, 1983), Chap. 8, pp. 211--284; Opt. Lett. 2, 94 (1978); 3, 205 (1978)] is not appropriate. The prediction by the steady-state theory has shown the DFWM to decrease with increasing laser-pump intensity as a function of 1/

{\mathrm{I}}_{\mathrm{laser}}

, which disagrees with the saturation behavior observed in the experiment. To elucidate the dependence of DFWM on the laser pump intensity, a non-steady-state extension of the nonperturbative theory of Abrams and Lind is required. The non-steady-state theoretical result will be shown to be in good agreement with the experimental power dependence at resonance transient DFWM especially in the high-power pump region.