Physical Review A

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

M. Anscombe, Rebeca de Nalda, İbrahim Küçükkara, J. P. Marangos

Published Oct 8, 2003• 2 citations

Abstract

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.

DOI: 10.1103/physreva.68.043810

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Generation of tunable coherent radiation below 1000 Å by four-wave mixing in krypton

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Coherent, narrow-band, tunable radiation in the extreme-ultraviolet spectral region was generated by a two-photon resonantly enhanced four-wave mixing process in krypton. Sum-generated radiation was produced near 942, 928, and 923 A with power efficiencies as high as 10−5. Difference-generated radiation near 1312 Å was also detected.

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Physical Review A

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

M. Anscombe, Rebeca de Nalda, İbrahim Küçükkara, J. P. Marangos

Published Oct 8, 2003• 2 citations

Publisher

Abstract

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.

DOI: 10.1103/physreva.68.043810

Related papers

Near-resonant four-wave mixing of attosecond extreme-ultraviolet pulses with near-infrared pulses in neon: Detection of electronic coherences

Wei Cao, Erika R. Warrick, Ashley P. Fidler +2 more

Coherent narrow-band extreme-ultraviolet (EUV) light is generated by a near-resonant four-wave mixing (FWM) process between attosecond pulse trains and near-infrared pulses in neon gas. The near-resonant FWM process involves one vacuum-ultraviolet (VUV) photon and two near-infrared (NIR) photons and produces new higher-energy frequency components corresponding to the $ns/nd$ to ground-state $(2{s}^{2}2{p}^{6})$ transitions in the neon atom. The EUV emission exhibits small angular divergence (2 mrad) and monotonically increasing intensity over a pressure range of 0.5--16 Torr, suggesting phase matching in the production of the narrow-bandwidth coherent EUV light. In addition, time-resolved scans of the NIR nonlinear mixing process reveal the detection of a persistent, ultrafast bound electronic wave packet based on a coherent superposition initiated by the VUV pulse in the neon atoms. This FWM process using attosecond pulses offers a means for both efficient narrow-band EUV source generation and time-resolved investigations of ultrafast dynamics.Coherent narrow-band extreme-ultraviolet (EUV) light is generated by a near-resonant four-wave mixing (FWM) process between attosecond pulse trains and near-infrared pulses in neon gas. The near-resonant FWM process involves one vacuum-ultraviolet (VUV) photon and two near-infrared (NIR) photons and produces new higher-energy frequency components corresponding to the $ns/nd$ to ground-state $(2{s}^{2}2{p}^{6})$ transitions in the neon atom. The EUV emission exhibits small angular divergence (2 mrad) and monotonically increasing intensity over a pressure range of 0.5--16 Torr, suggesting phase matching in the production of the narrow-bandwidth coherent EUV light. In addition, time-resolved scans of the NIR nonlinear mixing process reveal the detection of a persistent, ultrafast bound electronic wave packet based on a coherent superposition initiated by the VUV pulse in the neon atoms. This FWM process using attosecond pulses offers a means for both efficient narrow-band EUV source generation and time-resolved investigations of ultrafast dynamics.

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Physical Review AJul 1, 199720 citations

Resonant sum-difference frequency mixing enhanced by electromagnetically induced transparency in krypton

C. Franklin Dorman, J. P. Marangos

We report experiments that investigate the generation of coherent VUV radiation at 123.6 nm via a resonant sum-difference frequency mixing scheme in Kr. One of the mixing fields at 212.55 nm was in two-photon resonance with the transition between the ${4p}^{6}{}^{1}S$ ground state and the ${4p}^{5}5p[0,\frac{1}{2}]$ excited state $(94093.7 {\mathrm{cm}}^{\ensuremath{-}1}).$ The second field (the coupling field) at 759 nm was in single-photon resonance with the transition between the ${4p}^{5}5p[0,\frac{1}{2}]$ state and the ${4p}^{5}5s[1,\frac{1}{2}]$ state at $80917.6 {\mathrm{cm}}^{\ensuremath{-}1}.$ The presence of the coupling field leads to electromagnetically induced transparency (EIT) at the wavelength of the generated field, 123.6 nm. This is predicted to enhance the four-wave-mixing efficiency by a large factor. We have studied the dependence of the four-wave mixing process on the detuning and strength of the coupling field. The efficiency for four-wave mixing was found to be enhanced by a significant factor (>5) by the EIT effect when the resonant coupling field strength exceeded about half the Doppler width $(0.1 {\mathrm{cm}}^{\ensuremath{-}1}).$ A calculation for monochromatic fields and a uniform slab of gas provided qualitative agreement with the results of experiment. The relative conversion efficiency for this resonant mixing scheme is found to be ${10}^{4}$ times greater than that for a similar scheme where the coupling laser is tuned far $(1270 {\mathrm{cm}}^{\ensuremath{-}1})$ off resonance. A substantial part of this resonant enhancement can thus be attributed to the EIT effect.We report experiments that investigate the generation of coherent VUV radiation at 123.6 nm via a resonant sum-difference frequency mixing scheme in Kr. One of the mixing fields at 212.55 nm was in two-photon resonance with the transition between the ${4p}^{6}{}^{1}S$ ground state and the ${4p}^{5}5p[0,\frac{1}{2}]$ excited state $(94093.7 {\mathrm{cm}}^{\ensuremath{-}1}).$ The second field (the coupling field) at 759 nm was in single-photon resonance with the transition between the ${4p}^{5}5p[0,\frac{1}{2}]$ state and the ${4p}^{5}5s[1,\frac{1}{2}]$ state at $80917.6 {\mathrm{cm}}^{\ensuremath{-}1}.$ The presence of the coupling field leads to electromagnetically induced transparency (EIT) at the wavelength of the generated field, 123.6 nm. This is predicted to enhance the four-wave-mixing efficiency by a large factor. We have studied the dependence of the four-wave mixing process on the detuning and strength of the coupling field. The efficiency for four-wave mixing was found to be enhanced by a significant factor (>5) by the EIT effect when the resonant coupling field strength exceeded about half the Doppler width $(0.1 {\mathrm{cm}}^{\ensuremath{-}1}).$ A calculation for monochromatic fields and a uniform slab of gas provided qualitative agreement with the results of experiment. The relative conversion efficiency for this resonant mixing scheme is found to be ${10}^{4}$ times greater than that for a similar scheme where the coupling laser is tuned far $(1270 {\mathrm{cm}}^{\ensuremath{-}1})$ off resonance. A substantial part of this resonant enhancement can thus be attributed to the EIT effect.

Physical Review ANov 1, 199818 citations

Investigation of vacuum ultraviolet generation in a resonant four-wave mixing scheme in krypton with electro-magnetically induced transparency

C. Franklin Dorman, J. P. Marangos, Jon C. Petch

We report experiments investigating a resonant sum-difference frequency mixing scheme in krypton producing coherent radiation at 123.6nm (i.e. in the vacuum ultraviolet (VUV)). Owing to the resonant nature of this scheme, electromagnetically induced transparency (EIT) plays a crucial role in the generation of this coherent radiation, resulting in a greatly enhanced conversion efficiency. This is the first time a resonant sum-difference mixing scheme involving EIT, that generates VUV radiation, has been investigated experimentally. Our results are in broad agreement with theoretical predictions. Measurements are presented of the dependence of VUV generation on laser detuning (in the range ± cm−1) and laser powers. In particular the dependence on the coupling field strength has been studied in the range of coupling field Rabi frequencies Ωc = 0.05−3 cm−1. We estimate an enhancement in the conversion efficiency, compared with the non-resonant case, of greater than 102.We report experiments investigating a resonant sum-difference frequency mixing scheme in krypton producing coherent radiation at 123.6nm (i.e. in the vacuum ultraviolet (VUV)). Owing to the resonant nature of this scheme, electromagnetically induced transparency (EIT) plays a crucial role in the generation of this coherent radiation, resulting in a greatly enhanced conversion efficiency. This is the first time a resonant sum-difference mixing scheme involving EIT, that generates VUV radiation, has been investigated experimentally. Our results are in broad agreement with theoretical predictions. Measurements are presented of the dependence of VUV generation on laser detuning (in the range ± cm−1) and laser powers. In particular the dependence on the coupling field strength has been studied in the range of coupling field Rabi frequencies Ωc = 0.05−3 cm−1. We estimate an enhancement in the conversion efficiency, compared with the non-resonant case, of greater than 102.

Journal of Modern OpticsJun 1, 19981 citation

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

Generation of tunable coherent radiation below 1000 Å by four-wave mixing in krypton

Keith Bonin, Thomas J. Mcilrath

Journal of the Optical Society of America BApr 1, 198529 citations

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{'}}

{15d}^{\ensuremath{'}}

ns/nd

to ground-state

(2{s}^{2}2{p}^{6})

transitions in the neon atom. The EUV emission exhibits small angular divergence (2 mrad) and monotonically increasing intensity over a pressure range of 0.5--16 Torr, suggesting phase matching in the production of the narrow-bandwidth coherent EUV light. In addition, time-resolved scans of the NIR nonlinear mixing process reveal the detection of a persistent, ultrafast bound electronic wave packet based on a coherent superposition initiated by the VUV pulse in the neon atoms. This FWM process using attosecond pulses offers a means for both efficient narrow-band EUV source generation and time-resolved investigations of ultrafast dynamics.

(n=4--8)

in atomic hydrogen. Pulsed radiation was generated by strong coupling of the

\mathrm{np}

and

2s

levels with laser radiation at Balmer wavelengths, and simultaneously (weaker) coupling of the

2s

and

1s

levels by two-photon resonance with 243-nm laser radiation. Investigations were carried out over a range of laser intensities and products of interaction length and atomic density

(\mathrm{NL}).

As the product

\mathrm{NL}

increased, the XUV intensities were greatly enhanced by EIT, and at high

\mathrm{NL}

values, the spectral distributions of some of the generated signals were found to be distorted by the presence of molecular hydrogen. Calculated profiles, modified to incorporate the effects of nearby molecular resonances, were shown to be in good agreement with the observed spectra.

{4p}^{6}{}^{1}S

ground state and the

{4p}^{5}5p[0,\frac{1}{2}]

excited state $(94093.7 {\mathrm{cm}}^{\ensuremath{-}1}).$ The second field (the coupling field) at 759 nm was in single-photon resonance with the transition between the

{4p}^{5}5p[0,\frac{1}{2}]

state and the

{4p}^{5}5s[1,\frac{1}{2}]

state at $80917.6 {\mathrm{cm}}^{\ensuremath{-}1}.$ The presence of the coupling field leads to electromagnetically induced transparency (EIT) at the wavelength of the generated field, 123.6 nm. This is predicted to enhance the four-wave-mixing efficiency by a large factor. We have studied the dependence of the four-wave mixing process on the detuning and strength of the coupling field. The efficiency for four-wave mixing was found to be enhanced by a significant factor (>5) by the EIT effect when the resonant coupling field strength exceeded about half the Doppler width $(0.1 {\mathrm{cm}}^{\ensuremath{-}1}).$ A calculation for monochromatic fields and a uniform slab of gas provided qualitative agreement with the results of experiment. The relative conversion efficiency for this resonant mixing scheme is found to be

{10}^{4}

times greater than that for a similar scheme where the coupling laser is tuned far $(1270 {\mathrm{cm}}^{\ensuremath{-}1})$ off resonance. A substantial part of this resonant enhancement can thus be attributed to the EIT effect.

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.