arXiv:1110.6258 · Physical Review A

Femtosecond transparency in the extreme-ultraviolet region

Michal Tarana, Chris H. Greene

Published Jan 12, 2012• 38 citations

Abstract

Electromagnetically-induced-transparency-like behavior in the extreme-ultraviolet region is studied theoretically, including the effect of intense 800 nm laser dressing of He 2s2p(${}^{1}\phantom{\rule{-0.16em}{0ex}}{P}^{o}$) and 2p${}^{2}$${(}^{1}\phantom{\rule{-0.16em}{0ex}}{S}^{e})$ autoionizing states. We present an ab initio solution of the time-dependent Schr\"odinger equation in an $LS$-coupling configuration-interaction basis set. The method enables a rigorous treatment of optical field ionization of these coupled autoionizing states into the $N=2$ continuum in addition to $N=1$. Our calculated transient absorption spectra show encouraging agreement with experiment.

DOI: 10.1103/physreva.85.013411

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Femtosecond XUV transparency in light-coupled He doubly excited states.

Michal Tarana, Chris H. Greene

Electromagnetically induced transparency-like behavior in extreme ultraviolet is studied theoretically, including the effect of laser dressing of He 2s2p(^1P^o) and 2p^2(^1S^e) autoionizing states by an intense 800 nm field. The method allows for a rigorous treatment of optical field ionization of these coupled autoionizing states into the N=2 continuum in addition to N=1. Our calculated transient absorption spectra show reasonably encouraging agreement with experiment.

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Transient absorption and reshaping of ultrafast XUV light by laser-dressed helium

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Suppression of laser-induced collisional autoionization through electromagnetically induced transparency

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arXiv:1110.6258 · Physical Review A

Femtosecond transparency in the extreme-ultraviolet region

Michal Tarana, Chris H. Greene

Published Jan 12, 2012• 38 citations

arXiv HTML PDF

Abstract

Electromagnetically-induced-transparency-like behavior in the extreme-ultraviolet region is studied theoretically, including the effect of intense 800 nm laser dressing of He 2s2p(

{}^{1}\phantom{\rule{-0.16em}{0ex}}{P}^{o}

) and 2p

{}^{2}$${(}^{1}\phantom{\rule{-0.16em}{0ex}}{S}^{e})

autoionizing states. We present an ab initio solution of the time-dependent Schr"odinger equation in an

LS

-coupling configuration-interaction basis set. The method enables a rigorous treatment of optical field ionization of these coupled autoionizing states into the

N=2

continuum in addition to

N=1

. Our calculated transient absorption spectra show encouraging agreement with experiment.

DOI: 10.1103/physreva.85.013411

Related papers

Femtosecond XUV transparency in light-coupled He doubly excited states.

Michal Tarana, Chris H. Greene

Frontiers in OpticsJan 1, 20110 citations

Transient absorption and reshaping of ultrafast XUV light by laser-dressed helium

Mette B. Gaarde, Christian Buth, Jennifer L. Tate +1 more

We present a theoretical study of transient absorption and reshaping of extreme ultraviolet (XUV) pulses by helium atoms dressed with a moderately strong infrared (IR) laser field. We formulate the atomic response using both the frequency-dependent absorption cross section and a time-frequency approach based on the time-dependent dipole induced by the light fields. The latter approach can be used in cases when an ultrafast dressing pulse induces transient effects, and/or when the atom exchanges energy with multiple frequency components of the XUV field. We first characterize the dressed atom response by calculating the frequency-dependent absorption cross section for XUV energies between 20 and 24 eV for several dressing wavelengths between 400 and 2000 nm and intensities up to 10 ${}^{12}$ W/cm ${}^{2}$ . We find that for dressing wavelengths near 1600 nm, there is an Autler-Townes splitting of the $1s\ensuremath{\rightarrow}2p$ transition that can potentially lead to transparency for absorption of XUV light tuned to this transition. We study the effect of this XUV transparency in a macroscopic helium gas by incorporating the time-frequency approach into a solution of the coupled Maxwell-Schr\"odinger equations. We find rich temporal reshaping dynamics when a 61-fs XUV pulse resonant with the $1s\ensuremath{\rightarrow}2p$ transition propagates through a helium gas dressed by an 11-fs, 1600-nm laser pulse.We present a theoretical study of transient absorption and reshaping of extreme ultraviolet (XUV) pulses by helium atoms dressed with a moderately strong infrared (IR) laser field. We formulate the atomic response using both the frequency-dependent absorption cross section and a time-frequency approach based on the time-dependent dipole induced by the light fields. The latter approach can be used in cases when an ultrafast dressing pulse induces transient effects, and/or when the atom exchanges energy with multiple frequency components of the XUV field. We first characterize the dressed atom response by calculating the frequency-dependent absorption cross section for XUV energies between 20 and 24 eV for several dressing wavelengths between 400 and 2000 nm and intensities up to 10${}^{12}$ W/cm${}^{2}$. We find that for dressing wavelengths near 1600 nm, there is an Autler-Townes splitting of the $1s\ensuremath{\rightarrow}2p$ transition that can potentially lead to transparency for absorption of XUV light tuned to this transition. We study the effect of this XUV transparency in a macroscopic helium gas by incorporating the time-frequency approach into a solution of the coupled Maxwell-Schr\"odinger equations. We find rich temporal reshaping dynamics when a 61-fs XUV pulse resonant with the $1s\ensuremath{\rightarrow}2p$ transition propagates through a helium gas dressed by an 11-fs, 1600-nm laser pulse.

arXiv:1010.4558Physical Review AJan 31, 2011182 citations

Suppression of laser-induced collisional autoionization through electromagnetically induced transparency

Roberto Buffa

The effect of electromagnetically induced transparency on laser-induced collisional autoionization is investigated. The process, occurring only during atomic collisions and transient in nature, is characterized by the formation of a quasimolecule that can be ionized through the excitation to a pair of interfering dressed states decaying into the same continuum of ionization. Ionization suppression of the order of 70% is predicted for dressing laser intensities of the order of a few tens of MW/ ${\mathrm{cm}}^{2}$ . \textcopyright{} 1996 The American Physical Society.The effect of electromagnetically induced transparency on laser-induced collisional autoionization is investigated. The process, occurring only during atomic collisions and transient in nature, is characterized by the formation of a quasimolecule that can be ionized through the excitation to a pair of interfering dressed states decaying into the same continuum of ionization. Ionization suppression of the order of 70% is predicted for dressing laser intensities of the order of a few tens of MW/${\mathrm{cm}}^{2}$. \textcopyright{} 1996 The American Physical Society.

Physical Review AJan 1, 19962 citations

Role of atomic coherence effects in four-wave mixing using autoionizing resonances

M. Anscombe, Rebeca de Nalda, İbrahim Küçükkara +1 more

The generation of tunable, nanosecond-pulsed extreme-ultraviolet (EUV) light $(84.92\mathrm{nm}$ to $84.97\mathrm{nm}$ $\ensuremath{\sim}14.6\mathrm{eV})$ using four-wave mixing in optically deep krypton gas was investigated experimentally and theoretically. The sum-frequency mixing scheme generated light from two overlapping autoionizing resonances, ${17s}^{\ensuremath{'}}$ and ${15d}^{\ensuremath{'}}$. We investigated whether the laser-induced atomic coherence effect of electromagnetically induced transparency (EIT) could enhance the intensity of the EUV light generated. The maximum EUV output was seen from the region where the ${15d}^{\ensuremath{'}}$ autoionizing resonance has a transparency window due to Fano-type quantum interference. An analytical model using appropriate atomic parameters explains how background absorption can prevent EIT enhancement of EUV generation; and shows how a background Raman-like coupling term in the nonlinear susceptibility can well describe the measured EUV generation spectrum.The generation of tunable, nanosecond-pulsed extreme-ultraviolet (EUV) light $(84.92\mathrm{nm}$ to $84.97\mathrm{nm}$ $\ensuremath{\sim}14.6\mathrm{eV})$ using four-wave mixing in optically deep krypton gas was investigated experimentally and theoretically. The sum-frequency mixing scheme generated light from two overlapping autoionizing resonances, ${17s}^{\ensuremath{'}}$ and ${15d}^{\ensuremath{'}}$. We investigated whether the laser-induced atomic coherence effect of electromagnetically induced transparency (EIT) could enhance the intensity of the EUV light generated. The maximum EUV output was seen from the region where the ${15d}^{\ensuremath{'}}$ autoionizing resonance has a transparency window due to Fano-type quantum interference. An analytical model using appropriate atomic parameters explains how background absorption can prevent EIT enhancement of EUV generation; and shows how a background Raman-like coupling term in the nonlinear susceptibility can well describe the measured EUV generation spectrum.

Physical Review AOct 8, 20032 citations

Photoionization suppression by continuum coherence: Experiment and theory

Леонід Петрович Яценко, Thomas Halfmann, Bruce W. Shore +1 more

We present experimental and theoretical results of a detailed study of laser-induced continuum structures (LICS's) in the photoionization continuum of helium out of the metastable state $2s{}^{1}{S}_{0}.$ The continuum dressing, with a 1064-nm laser, couples the same region of the continuum to the $4s{}^{1}{S}_{0}$ state. The experimental data, presented for a range of intensities, show pronounced ionization suppression (by as much as 70% with respect to the far-from-resonance value) as well as enhancement, in a Beutler-Fano resonance profile. This ionization suppression is a clear indication of population trapping mediated by coupling to a continuum. We present experimental results demonstrating the effect of pulse delay upon the LICS's, and for the behavior of LICS's for both weak and strong probe pulses. Simulations based upon numerical solution of the Schr\"odinger equation model the experimental results. The atomic parameters (Rabi frequencies and Stark shifts) are calculated using a simple model-potential method for the computation of the needed wave functions. The simulations of the LICS profiles are in excellent agreement with experiment. We also present an analytic formulation of pulsed LICS's. We show that in the case of a probe pulse shorter than the dressing one, the LICS profile is the convolution of the power spectra of the probe pulse with the usual Fano profile of stationary LICS's. We discuss some consequences of deviation from steady-state theory.We present experimental and theoretical results of a detailed study of laser-induced continuum structures (LICS's) in the photoionization continuum of helium out of the metastable state $2s{}^{1}{S}_{0}.$ The continuum dressing, with a 1064-nm laser, couples the same region of the continuum to the $4s{}^{1}{S}_{0}$ state. The experimental data, presented for a range of intensities, show pronounced ionization suppression (by as much as 70% with respect to the far-from-resonance value) as well as enhancement, in a Beutler-Fano resonance profile. This ionization suppression is a clear indication of population trapping mediated by coupling to a continuum. We present experimental results demonstrating the effect of pulse delay upon the LICS's, and for the behavior of LICS's for both weak and strong probe pulses. Simulations based upon numerical solution of the Schr\"odinger equation model the experimental results. The atomic parameters (Rabi frequencies and Stark shifts) are calculated using a simple model-potential method for the computation of the needed wave functions. The simulations of the LICS profiles are in excellent agreement with experiment. We also present an analytic formulation of pulsed LICS's. We show that in the case of a probe pulse shorter than the dressing one, the LICS profile is the convolution of the power spectra of the probe pulse with the usual Fano profile of stationary LICS's. We discuss some consequences of deviation from steady-state theory.

arXiv:physics/9901017Physical Review AApr 1, 199949 citations

Photoabsorption of attosecond XUV light pulses by two strongly laser-coupled autoionizing states

Wei-Chun Chu, C. D. Lin

We study theoretically the photoabsorption spectra of an attosecond extreme ultraviolet (XUV) pulse by a laser-dressed atomic system. A weak XUV excites an autoionizing state which is strongly coupled to another autoionizing state by a laser. The theory was applied to explain two recent experiments [Loh, Greene, and Leone, Chem. Phys. 350, 7 (2008); Wang, Chini, Chen, Zhang, Cheng, He, Cheng, Wu, Thumm, and Chang, Phys. Rev. Lett. 105, 143002 (2010)] where the absorption spectra of the XUV lights were measured against the time delay between the laser and the XUV. In another example, we study an attosecond pulse exciting the $2s2p{(}^{1}\phantom{\rule{-0.16em}{0ex}}P)$ resonance of helium which is resonantly coupled to the $2{s}^{2}{(}^{1}\phantom{\rule{-0.16em}{0ex}}S)$ resonance by a moderately intense 540-nm laser. The relation between the photoabsorption spectra and the photoelectron spectra and the modification of the transmitted lights in such an experiment are analyzed. The role of Rabi flopping between the two autoionizing states within their lifetimes is investigated with respect to the laser intensity and detuning.We study theoretically the photoabsorption spectra of an attosecond extreme ultraviolet (XUV) pulse by a laser-dressed atomic system. A weak XUV excites an autoionizing state which is strongly coupled to another autoionizing state by a laser. The theory was applied to explain two recent experiments [Loh, Greene, and Leone, Chem. Phys. 350, 7 (2008); Wang, Chini, Chen, Zhang, Cheng, He, Cheng, Wu, Thumm, and Chang, Phys. Rev. Lett. 105, 143002 (2010)] where the absorption spectra of the XUV lights were measured against the time delay between the laser and the XUV. In another example, we study an attosecond pulse exciting the $2s2p{(}^{1}\phantom{\rule{-0.16em}{0ex}}P)$ resonance of helium which is resonantly coupled to the $2{s}^{2}{(}^{1}\phantom{\rule{-0.16em}{0ex}}S)$ resonance by a moderately intense 540-nm laser. The relation between the photoabsorption spectra and the photoelectron spectra and the modification of the transmitted lights in such an experiment are analyzed. The role of Rabi flopping between the two autoionizing states within their lifetimes is investigated with respect to the laser intensity and detuning.

arXiv:1205.4766Physical Review AJan 11, 201245 citations

Electromagnetically-induced-transparency-like behavior in the extreme-ultraviolet region is studied theoretically, including the effect of intense 800 nm laser dressing of He 2s2p(

{}^{1}\phantom{\rule{-0.16em}{0ex}}{P}^{o}

) and 2p

{}^{2}$${(}^{1}\phantom{\rule{-0.16em}{0ex}}{S}^{e})

autoionizing states. We present an ab initio solution of the time-dependent Schr"odinger equation in an

LS

-coupling configuration-interaction basis set. The method enables a rigorous treatment of optical field ionization of these coupled autoionizing states into the

N=2

continuum in addition to

N=1

. Our calculated transient absorption spectra show encouraging agreement with experiment.

{}^{12}

W/cm

{}^{2}

. We find that for dressing wavelengths near 1600 nm, there is an Autler-Townes splitting of the $1s\ensuremath{\rightarrow}2p$ transition that can potentially lead to transparency for absorption of XUV light tuned to this transition. We study the effect of this XUV transparency in a macroscopic helium gas by incorporating the time-frequency approach into a solution of the coupled Maxwell-Schr\"odinger equations. We find rich temporal reshaping dynamics when a 61-fs XUV pulse resonant with the $1s\ensuremath{\rightarrow}2p$ transition propagates through a helium gas dressed by an 11-fs, 1600-nm laser pulse.

{\mathrm{cm}}^{2}

. \textcopyright{} 1996 The American Physical Society.

The generation of tunable, nanosecond-pulsed extreme-ultraviolet (EUV) light

(84.92\mathrm{nm}

84.97\mathrm{nm}

$\ensuremath{\sim}14.6\mathrm{eV})$ using four-wave mixing in optically deep krypton gas was investigated experimentally and theoretically. The sum-frequency mixing scheme generated light from two overlapping autoionizing resonances, ${17s}^{\ensuremath{'}}$ and ${15d}^{\ensuremath{'}}$. We investigated whether the laser-induced atomic coherence effect of electromagnetically induced transparency (EIT) could enhance the intensity of the EUV light generated. The maximum EUV output was seen from the region where the ${15d}^{\ensuremath{'}}$ autoionizing resonance has a transparency window due to Fano-type quantum interference. An analytical model using appropriate atomic parameters explains how background absorption can prevent EIT enhancement of EUV generation; and shows how a background Raman-like coupling term in the nonlinear susceptibility can well describe the measured EUV generation spectrum.

We present experimental and theoretical results of a detailed study of laser-induced continuum structures (LICS's) in the photoionization continuum of helium out of the metastable state

2s{}^{1}{S}_{0}.

The continuum dressing, with a 1064-nm laser, couples the same region of the continuum to the

4s{}^{1}{S}_{0}

state. The experimental data, presented for a range of intensities, show pronounced ionization suppression (by as much as 70% with respect to the far-from-resonance value) as well as enhancement, in a Beutler-Fano resonance profile. This ionization suppression is a clear indication of population trapping mediated by coupling to a continuum. We present experimental results demonstrating the effect of pulse delay upon the LICS's, and for the behavior of LICS's for both weak and strong probe pulses. Simulations based upon numerical solution of the Schr\"odinger equation model the experimental results. The atomic parameters (Rabi frequencies and Stark shifts) are calculated using a simple model-potential method for the computation of the needed wave functions. The simulations of the LICS profiles are in excellent agreement with experiment. We also present an analytic formulation of pulsed LICS's. We show that in the case of a probe pulse shorter than the dressing one, the LICS profile is the convolution of the power spectra of the probe pulse with the usual Fano profile of stationary LICS's. We discuss some consequences of deviation from steady-state theory.

2s2p{(}^{1}\phantom{\rule{-0.16em}{0ex}}P)

resonance of helium which is resonantly coupled to the

2{s}^{2}{(}^{1}\phantom{\rule{-0.16em}{0ex}}S)

resonance by a moderately intense 540-nm laser. The relation between the photoabsorption spectra and the photoelectron spectra and the modification of the transmitted lights in such an experiment are analyzed. The role of Rabi flopping between the two autoionizing states within their lifetimes is investigated with respect to the laser intensity and detuning.