arXiv:2106.11131 · Physical Review A

Resonant nonlinear refraction of 4–5−μm light in CO and CO2 gas

J. J. Pigeon, D. Tovey, Sergei Ya. Tochitsky, G. J. Louwrens, I. Ben‐Zvi, Dmitry V. Martyshkin, Vladimir Fedorov, K. Karki, Sergey Mirov, C. Joshi

Published Oct 21, 2021• 2 citations

arXiv HTML PDF

Abstract

The resonant nonlinear refraction of $4\text{--}5\text{\ensuremath{-}}\ensuremath{\mu}\text{m}$ light in CO and $\mathrm{C}{\mathrm{O}}_{2}$ gas at a peak intensity of $15\phantom{\rule{0.16em}{0ex}}\mathrm{MW}/\mathrm{c}{\mathrm{m}}^{2}$ was demonstrated using time- and frequency-resolved measurements of self-focusing and self-defocusing. The nonlinearity of these molecular gases exhibits intensity-dependent sign reversals and a $<4\text{\ensuremath{-}}\mathrm{ns}$ response time. A change from self-focusing to self-defocusing or vice versa was observed to occur for Rabi frequencies that are comparable to the collisional linewidth. A density matrix model for the nonlinear susceptibility of a strongly driven two-level system provides a qualitative explanation for these results.

DOI: 10.1103/physreva.104.043519

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Negative nonlinear susceptibility of cesium vapor around 1.06 μm

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arXiv:2106.11131 · Physical Review A

Resonant nonlinear refraction of 4–5−μm light in CO and CO2 gas

J. J. Pigeon, D. Tovey, Sergei Ya. Tochitsky, G. J. Louwrens, I. Ben‐Zvi, Dmitry V. Martyshkin, Vladimir Fedorov, K. Karki, Sergey Mirov, C. Joshi

Published Oct 21, 2021• 2 citations

arXiv HTML PDF

Abstract

The resonant nonlinear refraction of

4\text{--}5\text{\ensuremath{-}}\ensuremath{\mu}\text{m}

light in CO and

\mathrm{C}{\mathrm{O}}_{2}

gas at a peak intensity of

15\phantom{\rule{0.16em}{0ex}}\mathrm{MW}/\mathrm{c}{\mathrm{m}}^{2}

was demonstrated using time- and frequency-resolved measurements of self-focusing and self-defocusing. The nonlinearity of these molecular gases exhibits intensity-dependent sign reversals and a

<4\text{\ensuremath{-}}\mathrm{ns}

response time. A change from self-focusing to self-defocusing or vice versa was observed to occur for Rabi frequencies that are comparable to the collisional linewidth. A density matrix model for the nonlinear susceptibility of a strongly driven two-level system provides a qualitative explanation for these results.

DOI: 10.1103/physreva.104.043519

Related papers

Negative nonlinear susceptibility of cesium vapor around 1.06 μm

Robert H. Lehmberg, John F. Reintjes, Robert C Eckardt

We outline a complete theory of the nonlinear susceptibility of cesium around 1.06 \ensuremath{\mu}m, and present the first measurements of the negative nonlinear refractive index ${n}_{2}$ primarily responsible for the self-defocusing that is observed. For linearly polarized light, our measured value of ${n}_{2}$ is $\ensuremath{-}(1.4\ifmmode\pm\else\textpm\fi{}0.2)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}30}N$ esu, where $N$ is the atomic density. This is in reasonable agreement with our calculated value of $\ensuremath{-}2.62\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}30}N$. The main portion of ${n}_{2}$ comes from a two-photon resonance between the $6s$ and $7s$ levels, and an additional negative term arises from induced population changes between $6s$ and $6p$ . For circular polarization, ${n}_{2}$ arises mainly from the induced population changes, giving the measured and calculated values of $\ensuremath{-}(0.26\ifmmode\pm\else\textpm\fi{}0.03)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}30}N$ and $\ensuremath{-}0.525\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}30}N$, respectively. In our experiments where the 35-psec pulses were shorter than the $6s\ensuremath{-}6p$ inverse linewidth, the nonlinear susceptibility depends mainly on the instantaneous intensity; however, for longer pulses, one would obtain additional contributions proportional to time integrals over the intensity. Since the useful output power from large Nd laser systems is limited by self-focusing due to the laser glass, our results suggest the possibility of increasing this power by using Cs vapor for compensation.We outline a complete theory of the nonlinear susceptibility of cesium around 1.06 \ensuremath{\mu}m, and present the first measurements of the negative nonlinear refractive index ${n}_{2}$ primarily responsible for the self-defocusing that is observed. For linearly polarized light, our measured value of ${n}_{2}$ is $\ensuremath{-}(1.4\ifmmode\pm\else\textpm\fi{}0.2)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}30}N$ esu, where $N$ is the atomic density. This is in reasonable agreement with our calculated value of $\ensuremath{-}2.62\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}30}N$. The main portion of ${n}_{2}$ comes from a two-photon resonance between the $6s$ and $7s$ levels, and an additional negative term arises from induced population changes between $6s$ and $6p$. For circular polarization, ${n}_{2}$ arises mainly from the induced population changes, giving the measured and calculated values of $\ensuremath{-}(0.26\ifmmode\pm\else\textpm\fi{}0.03)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}30}N$ and $\ensuremath{-}0.525\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}30}N$, respectively. In our experiments where the 35-psec pulses were shorter than the $6s\ensuremath{-}6p$ inverse linewidth, the nonlinear susceptibility depends mainly on the instantaneous intensity; however, for longer pulses, one would obtain additional contributions proportional to time integrals over the intensity. Since the useful output power from large Nd laser systems is limited by self-focusing due to the laser glass, our results suggest the possibility of increasing this power by using Cs vapor for compensation.

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Robert G. Harrison, W. J. Firth, I. A. Al-Saidi +1 more

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International Meeting on Instabilities and Dynamics of Lasers and Nonlinear Optical SystemsJan 1, 19850 citations

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Christian Kohler, Roland Guichard, Emmanuel Lorin +4 more

Accurate modeling of optical nonlinearities is crucial to describe macroscopic laser propagation in a medium, including sum frequency generation, spectral broadening due to self-phase modulation, various ionization processes and soliton formation. For incident laser light the response of the medium is given by the induced polarization of the microscopic system. The polarization is usually expanded in a Taylor series for the electric field amplitude, which is truncated after the first non-linear term being of third order for isotropic media. A third-order nonlinearity leads to the well-known optical Kerr effect, where the refractive index of the medium becomes intensity dependent via n = n0+ n2I. This leads to an inherent problem when modeling laser propagation in two or more spatial dimensions, linked to the formal divergence (n2> 0) of the refractive index for increasing intensity.Accurate modeling of optical nonlinearities is crucial to describe macroscopic laser propagation in a medium, including sum frequency generation, spectral broadening due to self-phase modulation, various ionization processes and soliton formation. For incident laser light the response of the medium is given by the induced polarization of the microscopic system. The polarization is usually expanded in a Taylor series for the electric field amplitude, which is truncated after the first non-linear term being of third order for isotropic media. A third-order nonlinearity leads to the well-known optical Kerr effect, where the refractive index of the medium becomes intensity dependent via n = n0+ n2I. This leads to an inherent problem when modeling laser propagation in two or more spatial dimensions, linked to the formal divergence (n2> 0) of the refractive index for increasing intensity.

Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC)May 1, 20130 citations

Saturable refraction and reverse saturable refraction in optical materials

Chunfei Li, Yuxiao Wang

Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIEOct 13, 19981 citation

The resonant nonlinear refraction of

4\text{--}5\text{\ensuremath{-}}\ensuremath{\mu}\text{m}

light in CO and

\mathrm{C}{\mathrm{O}}_{2}

gas at a peak intensity of

15\phantom{\rule{0.16em}{0ex}}\mathrm{MW}/\mathrm{c}{\mathrm{m}}^{2}

was demonstrated using time- and frequency-resolved measurements of self-focusing and self-defocusing. The nonlinearity of these molecular gases exhibits intensity-dependent sign reversals and a

<4\text{\ensuremath{-}}\mathrm{ns}

We outline a complete theory of the nonlinear susceptibility of cesium around 1.06 \ensuremath{\mu}m, and present the first measurements of the negative nonlinear refractive index

{n}_{2}

primarily responsible for the self-defocusing that is observed. For linearly polarized light, our measured value of

{n}_{2}

is $\ensuremath{-}(1.4\ifmmode\pm\else\textpm\fi{}0.2)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}30}N$ esu, where

N

is the atomic density. This is in reasonable agreement with our calculated value of $\ensuremath{-}2.62\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}30}N$. The main portion of

{n}_{2}

comes from a two-photon resonance between the

6s

and

7s

levels, and an additional negative term arises from induced population changes between

6s

and

6p

. For circular polarization,

{n}_{2}

arises mainly from the induced population changes, giving the measured and calculated values of $\ensuremath{-}(0.26\ifmmode\pm\else\textpm\fi{}0.03)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}30}N$ and $\ensuremath{-}0.525\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}30}N$, respectively. In our experiments where the 35-psec pulses were shorter than the $6s\ensuremath{-}6p$ inverse linewidth, the nonlinear susceptibility depends mainly on the instantaneous intensity; however, for longer pulses, one would obtain additional contributions proportional to time integrals over the intensity. Since the useful output power from large Nd laser systems is limited by self-focusing due to the laser glass, our results suggest the possibility of increasing this power by using Cs vapor for compensation.