Frontiers in Optics

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

Michal Tarana, Chris H. Greene

Published Jan 1, 2011• 0 citations

Abstract

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.

DOI: 10.1364/ls.2011.lwc1

Related papers

Femtosecond transparency in the extreme-ultraviolet region

Michal Tarana, Chris H. Greene

arXiv:1110.6258Physical Review AJan 12, 201238 citations

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

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

arXiv:1010.4558Physical Review AJan 31, 2011182 citations

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

Wei-Chun Chu, C. D. Lin

arXiv:1205.4766Physical Review AJan 11, 201245 citations

Suppression of laser-induced collisional autoionization through electromagnetically induced transparency

Roberto Buffa

Physical Review AJan 1, 19962 citations

Strong-Field Extreme-Ultraviolet Dressing of Atomic Double Excitation

Christian Ott, Lennart Aufleger, Thomas Ding +21 more

arXiv:1907.06874Physical Review LettersOct 15, 201951 citations

Absorption and emission of single attosecond light pulses in an autoionizing gaseous medium dressed by a time-delayed control field

Wei-Chun Chu, C. D. Lin

arXiv:1211.6172Physical Review AJan 16, 201345 citations

Frontiers in Optics

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

Michal Tarana, Chris H. Greene

Published Jan 1, 2011• 0 citations

Publisher

Abstract

DOI: 10.1364/ls.2011.lwc1

Related papers

Femtosecond transparency in the extreme-ultraviolet region

Michal Tarana, Chris H. Greene

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.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.

arXiv:1110.6258Physical Review AJan 12, 201238 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

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

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

Strong-Field Extreme-Ultraviolet Dressing of Atomic Double Excitation

Christian Ott, Lennart Aufleger, Thomas Ding +21 more

We report on the experimental observation of a strong-field dressing of an autoionizing two-electron state in helium with intense extreme-ultraviolet laser pulses from a free-electron laser. The asymmetric Fano line shape of this transition is spectrally resolved, and we observe modifications of the resonance asymmetry structure for increasing free-electron-laser pulse energy on the order of few tens of Microjoules. A quantum-mechanical calculation of the time-dependent dipole response of this autoionizing state, driven by classical extreme-ultraviolet (XUV) electric fields, evidences strong-field-induced energy and phase shifts of the doubly excited state, which are extracted from the Fano line-shape asymmetry. The experimental results obtained at the Free-Electron Laser in Hamburg (FLASH) thus correspond to transient energy shifts on the order of a few meV, induced by strong XUV fields. These results open up a new way of performing nonperturbative XUV nonlinear optics for the light-matter interaction of resonant electronic transitions in atoms at short wavelengths.We report on the experimental observation of a strong-field dressing of an autoionizing two-electron state in helium with intense extreme-ultraviolet laser pulses from a free-electron laser. The asymmetric Fano line shape of this transition is spectrally resolved, and we observe modifications of the resonance asymmetry structure for increasing free-electron-laser pulse energy on the order of few tens of Microjoules. A quantum-mechanical calculation of the time-dependent dipole response of this autoionizing state, driven by classical extreme-ultraviolet (XUV) electric fields, evidences strong-field-induced energy and phase shifts of the doubly excited state, which are extracted from the Fano line-shape asymmetry. The experimental results obtained at the Free-Electron Laser in Hamburg (FLASH) thus correspond to transient energy shifts on the order of a few meV, induced by strong XUV fields. These results open up a new way of performing nonperturbative XUV nonlinear optics for the light-matter interaction of resonant electronic transitions in atoms at short wavelengths.

arXiv:1907.06874Physical Review LettersOct 15, 201951 citations

Absorption and emission of single attosecond light pulses in an autoionizing gaseous medium dressed by a time-delayed control field

Wei-Chun Chu, C. D. Lin

An extreme ultraviolet (EUV) single attosecond pulse passing through a laser-dressed dense gas is studied theoretically. The weak EUV pulse pumps the helium gas from the ground state to the $2s2p({}^{1}P)$ autoionizing state, which is coupled to the $2{s}^{2}{(}^{1}S)$ autoionizing state by a femtosecond infrared laser with the intensity in the order of 10 ${}^{12}$ W/cm ${}^{2}$ . The simulation shows how the transient absorption and emission of the EUV are modified by the coupling laser. A simple analytical expression for the atomic response derived for $\ensuremath{\delta}$-function pulses reveals the strong modification of the Fano lineshape in the spectra, where these features are quite universal and remain valid for realistic pulse conditions. We further account for the propagation of pulses in the medium and show that the EUV signal at the atomic resonance can be enhanced in the gaseous medium by more than 50 $%$ for specifically adjusted laser parameters, and that this enhancement persists as the EUV propagates in the gaseous medium. Our result demonstrates the high-level control of nonlinear optical effects that are achievable with attosecond pulses.An extreme ultraviolet (EUV) single attosecond pulse passing through a laser-dressed dense gas is studied theoretically. The weak EUV pulse pumps the helium gas from the ground state to the $2s2p({}^{1}P)$ autoionizing state, which is coupled to the $2{s}^{2}{(}^{1}S)$ autoionizing state by a femtosecond infrared laser with the intensity in the order of 10${}^{12}$ W/cm${}^{2}$. The simulation shows how the transient absorption and emission of the EUV are modified by the coupling laser. A simple analytical expression for the atomic response derived for $\ensuremath{\delta}$-function pulses reveals the strong modification of the Fano lineshape in the spectra, where these features are quite universal and remain valid for realistic pulse conditions. We further account for the propagation of pulses in the medium and show that the EUV signal at the atomic resonance can be enhanced in the gaseous medium by more than 50$%$ for specifically adjusted laser parameters, and that this enhancement persists as the EUV propagates in the gaseous medium. Our result demonstrates the high-level control of nonlinear optical effects that are achievable with attosecond pulses.

arXiv:1211.6172Physical Review AJan 16, 201345 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.

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.

{\mathrm{cm}}^{2}

. \textcopyright{} 1996 The American Physical Society.

An extreme ultraviolet (EUV) single attosecond pulse passing through a laser-dressed dense gas is studied theoretically. The weak EUV pulse pumps the helium gas from the ground state to the

2s2p({}^{1}P)

autoionizing state, which is coupled to the

2{s}^{2}{(}^{1}S)

autoionizing state by a femtosecond infrared laser with the intensity in the order of 10

{}^{12}

W/cm

{}^{2}

. The simulation shows how the transient absorption and emission of the EUV are modified by the coupling laser. A simple analytical expression for the atomic response derived for $\ensuremath{\delta}$-function pulses reveals the strong modification of the Fano lineshape in the spectra, where these features are quite universal and remain valid for realistic pulse conditions. We further account for the propagation of pulses in the medium and show that the EUV signal at the atomic resonance can be enhanced in the gaseous medium by more than 50

%

for specifically adjusted laser parameters, and that this enhancement persists as the EUV propagates in the gaseous medium. Our result demonstrates the high-level control of nonlinear optical effects that are achievable with attosecond pulses.