The line shape and strength of two-photon absorption in an atomic vapor are studied both theoretically and experimentally for the case of absorption of unequal-frequency photons. Special attention is given to the situation in which the intermediate state is resonant or nearly resonant. It is shown that for the resonant case, maximum absorption rates and Doppler-free spectra are simultaneously obtained. Either counterpropagating or copropagating beams can be used. With counterpropagating beams the two-photon linewidths are quite insensitive to power broadening of the intermediate state. With copropagating beams the two-photon spectra can also reveal the intermediate-state structure with a resolution determined mainly by the intermediate-state lifetime (nearly as well as can be done using any spectroscopic technique). The theoretical analysis provides a closed-form solution for the line shape and strength of the two-photon spectrum. In general the line shape is composed of two features. One is Doppler broadened and predominates when the intermediate state is nonresonant. The second feature is Doppler free, and it predominates with a resonant intermediate state. Detailed comparisons of experimental measurements of the line shape and strength of two-photon absorption in Na vapor are made with the theory and found to be in excellent agreement. Signal strengths for the onresonance case are 6 \ifmmode\times\else\texttimes\fi{} ${10}^{9}$ larger than the case of equal-frequency photons with no loss in resolution.The line shape and strength of two-photon absorption in an atomic vapor are studied both theoretically and experimentally for the case of absorption of unequal-frequency photons. Special attention is given to the situation in which the intermediate state is resonant or nearly resonant. It is shown that for the resonant case, maximum absorption rates and Doppler-free spectra are simultaneously obtained. Either counterpropagating or copropagating beams can be used. With counterpropagating beams the two-photon linewidths are quite insensitive to power broadening of the intermediate state. With copropagating beams the two-photon spectra can also reveal the intermediate-state structure with a resolution determined mainly by the intermediate-state lifetime (nearly as well as can be done using any spectroscopic technique). The theoretical analysis provides a closed-form solution for the line shape and strength of the two-photon spectrum. In general the line shape is composed of two features. One is Doppler broadened and predominates when the intermediate state is nonresonant. The second feature is Doppler free, and it predominates with a resonant intermediate state. Detailed comparisons of experimental measurements of the line shape and strength of two-photon absorption in Na vapor are made with the theory and found to be in excellent agreement. Signal strengths for the onresonance case are 6 \ifmmode\times\else\texttimes\fi{} ${10}^{9}$ larger than the case of equal-frequency photons with no loss in resolution.

Physical Review AAug 1, 1976149 citations

Two-photon absorption in atomic gases

M. S. Pindzola

Physics of Electronic and Atomic Collisions: ICPEAC XJan 1, 19770 citations

Line Shape of Two-Photon Absorption in a Standing-Wave Field in a Gas

L. S. Vasilenko, V. P. Chebotaev, A. V. Shishaev

Jan 1, 1970131 citations

Refractive Index Enhancement with Vanishing Absorption in an Atomic Vapor

Nicholas Proite, Brett Unks, Jonathan Tyler Green +1 more

We report a proof-of-principle experiment where the refractive index of an atomic vapor is enhanced while maintaining vanishing absorption of the beam. The key idea is to drive alkali atoms in a vapor with appropriate control lasers and induce a gain resonance and an absorption resonance for a probe beam in a two-photon Raman configuration. The strength and the position of these two resonances can be manipulated by changing the parameters of the control lasers. By using the interference between these two resonances, we obtain an enhanced refractive index without an increase in the absorption.We report a proof-of-principle experiment where the refractive index of an atomic vapor is enhanced while maintaining vanishing absorption of the beam. The key idea is to drive alkali atoms in a vapor with appropriate control lasers and induce a gain resonance and an absorption resonance for a probe beam in a two-photon Raman configuration. The strength and the position of these two resonances can be manipulated by changing the parameters of the control lasers. By using the interference between these two resonances, we obtain an enhanced refractive index without an increase in the absorption.

arXiv:0807.2584Physical Review LettersSep 29, 200870 citations

Electromagnetically induced two-photon absorption reduction in sodium vapor

Jin-Yue Gao, Suhui Yang, Dong Wang +5 more

Summary form only given. It is well known that two-photon absorption can be greatly enhanced whenever a single photon energy approaches an allowed atomic transition. If more than one intermediate state exists, the two-photon absorption can be annihilated depending on the location of the intermediate states. In case there is only one intermediate state, a control laser can be applied to couple the intermediate state with other state to create two dressed states. Then, the medium can be made transparent against two-photon absorption in the presence of multiple pathways. We report the first observation of electromagnetically induced two-photon absorption reduction in sodium vapor.Summary form only given. It is well known that two-photon absorption can be greatly enhanced whenever a single photon energy approaches an allowed atomic transition. If more than one intermediate state exists, the two-photon absorption can be annihilated depending on the location of the intermediate states. In case there is only one intermediate state, a control laser can be applied to couple the intermediate state with other state to create two dressed states. Then, the medium can be made transparent against two-photon absorption in the presence of multiple pathways. We report the first observation of electromagnetically induced two-photon absorption reduction in sodium vapor.

Quantum Electronics and Laser Science ConferenceJan 20, 20030 citations

{10}^{9}

larger than the case of equal-frequency photons with no loss in resolution.