Physical review. B, Condensed matter

Nonequilibrium resonant-phonon-induced excess photon-echo dephasing

Yue Bai, Ravinder Kachru

Published Dec 1, 1992• 12 citations

Abstract

We demonstrate that the excitation-induced excess dephasing of photon echoes in ${\mathrm{Pr}}^{3+}$:${\mathrm{YA}1\mathrm{O}}_{3}$${(}^{3}$${\mathrm{H}}_{4}$${\mathrm{\ensuremath{-}}}^{1}$${\mathrm{D}}_{2}$) is predominantly induced by the 51-${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ resonant phonons associated with nonradiative relaxations of the excited ions. Instantaneous diffusion via direct ion-ion coupling is found to be much less important. The dephasing mechanism discussed should be applicable to all other systems where the relaxation of excited states involves nonradiative processes.

DOI: 10.1103/physrevb.46.13735

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Physical review. B, Condensed matter

Nonequilibrium resonant-phonon-induced excess photon-echo dephasing

Yue Bai, Ravinder Kachru

Published Dec 1, 1992• 12 citations

Publisher

Abstract

We demonstrate that the excitation-induced excess dephasing of photon echoes in

{\mathrm{Pr}}^{3+}

{\mathrm{YA}1\mathrm{O}}_{3}$${(}^{3}$${\mathrm{H}}_{4}$${\mathrm{\ensuremath{-}}}^{1}$${\mathrm{D}}_{2}

) is predominantly induced by the 51-

{\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}

resonant phonons associated with nonradiative relaxations of the excited ions. Instantaneous diffusion via direct ion-ion coupling is found to be much less important. The dephasing mechanism discussed should be applicable to all other systems where the relaxation of excited states involves nonradiative processes.

DOI: 10.1103/physrevb.46.13735

Related papers

Optically induced shifts in the frequency of the 3 H4 −1 D2 transition of Pr3+ in LaF3

Jiamin Zhang, THOMAS W. MOSSBERG

Photon-echo techniques were employed to measure the homogeneous dephasing rate of the 592.5-nm, $^{3}$ ${\mathit{H}}_{4\mathrm{\ensuremath{-}}}^{1}$ ${\mathit{D}}_{2}$ , transition of ${\mathrm{Pr}}^{3+}$ as experimental parameters affecting the number of ${\mathrm{Pr}}^{3+}$ ions optically excited were varied. These parameters include the dopant concentration and the intensity, carrier frequency, and bandwidth of the excitation pulses. Dephasing rates are found to contain a background contribution whose magnitude is dependent upon the specific crystal sample studied and a second contribution whose magnitude increases with the number of ${\mathrm{Pr}}^{3+}$ ions changing state in the course of the echo excitation sequence. The second contribution to the dephasing rate is attributed to the presence of optical instantaneous diffusion, i.e., the redistribution of ionic transition frequencies consequent to optical excitation, in the samples.Photon-echo techniques were employed to measure the homogeneous dephasing rate of the 592.5-nm, $^{3}$${\mathit{H}}_{4\mathrm{\ensuremath{-}}}^{1}$${\mathit{D}}_{2}$, transition of ${\mathrm{Pr}}^{3+}$ as experimental parameters affecting the number of ${\mathrm{Pr}}^{3+}$ ions optically excited were varied. These parameters include the dopant concentration and the intensity, carrier frequency, and bandwidth of the excitation pulses. Dephasing rates are found to contain a background contribution whose magnitude is dependent upon the specific crystal sample studied and a second contribution whose magnitude increases with the number of ${\mathrm{Pr}}^{3+}$ ions changing state in the course of the echo excitation sequence. The second contribution to the dephasing rate is attributed to the presence of optical instantaneous diffusion, i.e., the redistribution of ionic transition frequencies consequent to optical excitation, in the samples.

Physical review. B, Condensed matterSep 1, 19938 citations

Excess dephasing in photon-echo experiments arising from excitation-induced electronic level shifts

Huang Jin, J.M. Zhang, A. Lezama +1 more

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Physical Review LettersJul 3, 1989101 citations

Observation of a magnetic-field-induced resonance in the homogeneous dephasing time for the 1 D2 −3 H4 transition in Pr3+ : YAlO3

Baozhu Luo, Stefan Kröll

Using two-pulse photon echo excitation a strong resonance in the measured homogeneous dephasing time as a function of magnetic field is observed in the $^{3}$ ${\mathit{H}}_{4}$ ${\mathrm{\ensuremath{-}}}^{1}$ ${\mathit{D}}_{2}$ transition of ${\mathrm{Pr}}^{3+}$ : ${\mathrm{YAlO}}_{3}$ . The resonance could only be observed at low excitation energies since it otherwise was masked by excitation intensity dependent extra dephasing processes in the crystal. Thus intensity dependent dephasing processes may not only affect the apparent dephasing time of a system but may also mask other more subtle interactions in the materials studied. It is reasonable to assume that the type of resonance observed could be caused by Zeeman induced level crossings in the active ion or in the host crystal ions or, possibly, that it could be due to coincidences between Zeeman level transition frequencies. However, based on current data of the Pr: ${\mathrm{YAlO}}_{3}$ system the observed resonance could not be unambiguously tied to such effects. \textcopyright{} 1996 The American Physical Society.Using two-pulse photon echo excitation a strong resonance in the measured homogeneous dephasing time as a function of magnetic field is observed in the $^{3}$${\mathit{H}}_{4}$${\mathrm{\ensuremath{-}}}^{1}$${\mathit{D}}_{2}$ transition of ${\mathrm{Pr}}^{3+}$:${\mathrm{YAlO}}_{3}$. The resonance could only be observed at low excitation energies since it otherwise was masked by excitation intensity dependent extra dephasing processes in the crystal. Thus intensity dependent dephasing processes may not only affect the apparent dephasing time of a system but may also mask other more subtle interactions in the materials studied. It is reasonable to assume that the type of resonance observed could be caused by Zeeman induced level crossings in the active ion or in the host crystal ions or, possibly, that it could be due to coincidences between Zeeman level transition frequencies. However, based on current data of the Pr:${\mathrm{YAlO}}_{3}$ system the observed resonance could not be unambiguously tied to such effects. \textcopyright{} 1996 The American Physical Society.

Physical review. B, Condensed matterOct 1, 19962 citations

Optical dephasing by nonequilibrium phonons in LaF3

Richard S. Meltzer, R. M. Macfarlane

Phonon-induced coherence loss (PICL) is produced by a monoenergetic nonequilibrium distribution of phonons in ${\mathrm{LaF}}_{3}$ : ${\mathrm{Pr}}^{3+}$ . The phonons are generated by relaxation between excited states of the ${\mathrm{Pr}}^{3+}$ ion after selective excitation with a pulsed, tunable dye laser. The optical dephasing is observed from the effect on the free-induction decay of ${\mathrm{Pr}}^{3+}$ ions whose excited-state level separation is resonant with the phonons. It is shown that PICL is a sensitive detector of monoenergetic phonons, and can be used to study phonon dynamics. The observed rate of optical dephasing is reduced relative to an equivalent occupation of 23-${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ phonons produced thermally.Phonon-induced coherence loss (PICL) is produced by a monoenergetic nonequilibrium distribution of phonons in ${\mathrm{LaF}}_{3}$:${\mathrm{Pr}}^{3+}$. The phonons are generated by relaxation between excited states of the ${\mathrm{Pr}}^{3+}$ ion after selective excitation with a pulsed, tunable dye laser. The optical dephasing is observed from the effect on the free-induction decay of ${\mathrm{Pr}}^{3+}$ ions whose excited-state level separation is resonant with the phonons. It is shown that PICL is a sensitive detector of monoenergetic phonons, and can be used to study phonon dynamics. The observed rate of optical dephasing is reduced relative to an equivalent occupation of 23-${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ phonons produced thermally.

Physical review. B, Condensed matterJul 15, 198517 citations

Intensity-dependent photon-echo relaxation in rare-earth-doped crystals

Stefan Kröll, E. Y. Xu, M. K. Kim +2 more

Photon-echo-relaxation measurements made on the $^{3}\mathrm{H}_{4}$ ${\mathrm{\ensuremath{-}}}^{3}$ ${\mathrm{P}}_{0}$ transition of 0.01 at. % ${\mathrm{Pr}}^{3+}$ :YAG (where YAG represents yttrium aluminum garnet), $^{3}\mathrm{H}_{4}$ ${\mathrm{\ensuremath{-}}}^{1}$ ${\mathrm{D}}_{2}$ transition in 0.1 at. % ${\mathrm{Pr}}^{3+}$ : ${\mathrm{YAlO}}_{3}$ , and $^{7}\mathrm{F}_{0}$ ${\mathrm{\ensuremath{-}}}^{5}$ ${\mathrm{D}}_{0}$ transition in 0.25 at. % ${\mathrm{Eu}}^{3+}$ : ${\mathrm{YAlO}}_{3}$ show that the photon-echo relaxation rate increases when the intensities of the excitation pulses are increased. Although a part of the relaxation-rate increase in ${\mathrm{Pr}}^{3+}$ :YAG may be attributed to an instantaneous spectral diffusion (ISD) in which the presence of excited neighboring ${\mathrm{Pr}}^{3+}$ ions change the local field and the absorption frequency of the rare-earth ions, our data deviate significantly from the ISD-model predictions. An additional intensity-dependent relaxation mechanism is required to explain the results.Photon-echo-relaxation measurements made on the $^{3}\mathrm{H}_{4}$${\mathrm{\ensuremath{-}}}^{3}$${\mathrm{P}}_{0}$ transition of 0.01 at. % ${\mathrm{Pr}}^{3+}$:YAG (where YAG represents yttrium aluminum garnet), $^{3}\mathrm{H}_{4}$${\mathrm{\ensuremath{-}}}^{1}$${\mathrm{D}}_{2}$ transition in 0.1 at. % ${\mathrm{Pr}}^{3+}$:${\mathrm{YAlO}}_{3}$, and $^{7}\mathrm{F}_{0}$${\mathrm{\ensuremath{-}}}^{5}$${\mathrm{D}}_{0}$ transition in 0.25 at. % ${\mathrm{Eu}}^{3+}$:${\mathrm{YAlO}}_{3}$ show that the photon-echo relaxation rate increases when the intensities of the excitation pulses are increased. Although a part of the relaxation-rate increase in ${\mathrm{Pr}}^{3+}$:YAG may be attributed to an instantaneous spectral diffusion (ISD) in which the presence of excited neighboring ${\mathrm{Pr}}^{3+}$ ions change the local field and the absorption frequency of the rare-earth ions, our data deviate significantly from the ISD-model predictions. An additional intensity-dependent relaxation mechanism is required to explain the results.

Physical review. B, Condensed matterJun 1, 199033 citations

Photon-echo attenuation in rare-earth-ion-doped crystals

Stefan B. Altner, G. Zumofen, Urs P. Wild +1 more

We study the optical properties of rare-earth-ion-doped inorganic crystals with an emphasis on the dependence of two-pulse photon echoes on the excitation density in the system. The experimental investigations concentrate on ${\mathrm{Pr}}^{3+}$ : ${\mathrm{Nd}}^{3+}$ : ${\mathrm{Eu}}^{3+}$ codoped ${\mathrm{Y}}_{2}$ Si ${\mathrm{O}}_{5}$ and YAl ${\mathrm{O}}_{3}$ crystals at low temperatures. With two pulses of one laser the echo is induced in one ion species and with a third, "scrambler" pulse of a second laser another species is excited. These scrambler excitations lead to a dephasing and thus to an echo attenuation which depends on the strength, frequency, and time of the scrambler pulse. The spectral sensitivity of the echo attenuation is used for a spectroscopic technique: "photon-echo attenuation spectroscopy." As a function of the delay time ${t}_{s}$ between the scrambler pulse and the onset of the two-pulse echo sequence the attenuation shows a very specific behavior dictated by the excitation-induced frequency shifts (EFS's). For ${t}_{s}$ between the two echo-inducing pulses the echo intensity is partially regained by the "dephasing-rephasing balancing" of the reversible EFS's. For the theoretical description a stochastic model is introduced and the dephasing by excitation-induced lattice vibrations and by EFS's are analyzed in detail. The present results are discussed in the light of previous experimental and theoretical investigations.We study the optical properties of rare-earth-ion-doped inorganic crystals with an emphasis on the dependence of two-pulse photon echoes on the excitation density in the system. The experimental investigations concentrate on ${\mathrm{Pr}}^{3+}$:${\mathrm{Nd}}^{3+}$:${\mathrm{Eu}}^{3+}$ codoped ${\mathrm{Y}}_{2}$Si${\mathrm{O}}_{5}$ and YAl${\mathrm{O}}_{3}$ crystals at low temperatures. With two pulses of one laser the echo is induced in one ion species and with a third, "scrambler" pulse of a second laser another species is excited. These scrambler excitations lead to a dephasing and thus to an echo attenuation which depends on the strength, frequency, and time of the scrambler pulse. The spectral sensitivity of the echo attenuation is used for a spectroscopic technique: "photon-echo attenuation spectroscopy." As a function of the delay time ${t}_{s}$ between the scrambler pulse and the onset of the two-pulse echo sequence the attenuation shows a very specific behavior dictated by the excitation-induced frequency shifts (EFS's). For ${t}_{s}$ between the two echo-inducing pulses the echo intensity is partially regained by the "dephasing-rephasing balancing" of the reversible EFS's. For the theoretical description a stochastic model is introduced and the dephasing by excitation-induced lattice vibrations and by EFS's are analyzed in detail. The present results are discussed in the light of previous experimental and theoretical investigations.

Physical review. B, Condensed matterDec 15, 199622 citations

We demonstrate that the excitation-induced excess dephasing of photon echoes in

{\mathrm{Pr}}^{3+}

{\mathrm{YA}1\mathrm{O}}_{3}$${(}^{3}$${\mathrm{H}}_{4}$${\mathrm{\ensuremath{-}}}^{1}$${\mathrm{D}}_{2}

) is predominantly induced by the 51-

{\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}

Photon-echo techniques were employed to measure the homogeneous dephasing rate of the 592.5-nm,

^{3}

${\mathit{H}}_{4\mathrm{\ensuremath{-}}}^{1}$

{\mathit{D}}_{2}

, transition of

{\mathrm{Pr}}^{3+}

as experimental parameters affecting the number of

{\mathrm{Pr}}^{3+}

ions optically excited were varied. These parameters include the dopant concentration and the intensity, carrier frequency, and bandwidth of the excitation pulses. Dephasing rates are found to contain a background contribution whose magnitude is dependent upon the specific crystal sample studied and a second contribution whose magnitude increases with the number of

{\mathrm{Pr}}^{3+}

ions changing state in the course of the echo excitation sequence. The second contribution to the dephasing rate is attributed to the presence of optical instantaneous diffusion, i.e., the redistribution of ionic transition frequencies consequent to optical excitation, in the samples.

Working on the

^{7}\mathrm{F}_{0}

${\mathrm{\ensuremath{-}}}^{5}$

{\mathrm{D}}_{0}

transition of

{\mathrm{Eu}}^{3+}

{\mathrm{Y}}_{2}

{\mathrm{O}}_{3}

, we provide the first detailed characterization of excitation-induced shifts in optical transition frequencies and demonstrate their exaggeration of nominally homogeneous dephasing rates. The shifts (found to vary in rough proportion to the number of

{\mathrm{Eu}}^{3+}

ions excited and to be as small as one part in

{10}^{12}

) were identified through their unique signature in specially designed photon-echo experiments. The effects reported may constitute a rather general complication in optical measurements of homogeneous relaxation rates in solids.

Using two-pulse photon echo excitation a strong resonance in the measured homogeneous dephasing time as a function of magnetic field is observed in the

^{3}

{\mathit{H}}_{4}

${\mathrm{\ensuremath{-}}}^{1}$

{\mathit{D}}_{2}

transition of

{\mathrm{Pr}}^{3+}

{\mathrm{YAlO}}_{3}

. The resonance could only be observed at low excitation energies since it otherwise was masked by excitation intensity dependent extra dephasing processes in the crystal. Thus intensity dependent dephasing processes may not only affect the apparent dephasing time of a system but may also mask other more subtle interactions in the materials studied. It is reasonable to assume that the type of resonance observed could be caused by Zeeman induced level crossings in the active ion or in the host crystal ions or, possibly, that it could be due to coincidences between Zeeman level transition frequencies. However, based on current data of the Pr:

{\mathrm{YAlO}}_{3}

system the observed resonance could not be unambiguously tied to such effects. \textcopyright{} 1996 The American Physical Society.

Phonon-induced coherence loss (PICL) is produced by a monoenergetic nonequilibrium distribution of phonons in

{\mathrm{LaF}}_{3}

{\mathrm{Pr}}^{3+}

. The phonons are generated by relaxation between excited states of the

{\mathrm{Pr}}^{3+}

ion after selective excitation with a pulsed, tunable dye laser. The optical dephasing is observed from the effect on the free-induction decay of

{\mathrm{Pr}}^{3+}

ions whose excited-state level separation is resonant with the phonons. It is shown that PICL is a sensitive detector of monoenergetic phonons, and can be used to study phonon dynamics. The observed rate of optical dephasing is reduced relative to an equivalent occupation of 23-${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ phonons produced thermally.

Photon-echo-relaxation measurements made on the

^{3}\mathrm{H}_{4}

${\mathrm{\ensuremath{-}}}^{3}$

{\mathrm{P}}_{0}

transition of 0.01 at. %

{\mathrm{Pr}}^{3+}

:YAG (where YAG represents yttrium aluminum garnet),

^{3}\mathrm{H}_{4}

${\mathrm{\ensuremath{-}}}^{1}$

{\mathrm{D}}_{2}

transition in 0.1 at. %

{\mathrm{Pr}}^{3+}

{\mathrm{YAlO}}_{3}

, and

^{7}\mathrm{F}_{0}

${\mathrm{\ensuremath{-}}}^{5}$

{\mathrm{D}}_{0}

transition in 0.25 at. %

{\mathrm{Eu}}^{3+}

{\mathrm{YAlO}}_{3}

show that the photon-echo relaxation rate increases when the intensities of the excitation pulses are increased. Although a part of the relaxation-rate increase in

{\mathrm{Pr}}^{3+}

:YAG may be attributed to an instantaneous spectral diffusion (ISD) in which the presence of excited neighboring

{\mathrm{Pr}}^{3+}

ions change the local field and the absorption frequency of the rare-earth ions, our data deviate significantly from the ISD-model predictions. An additional intensity-dependent relaxation mechanism is required to explain the results.

{\mathrm{Pr}}^{3+}

{\mathrm{Nd}}^{3+}

{\mathrm{Eu}}^{3+}

codoped

{\mathrm{Y}}_{2}

{\mathrm{O}}_{5}

and YAl

{\mathrm{O}}_{3}

crystals at low temperatures. With two pulses of one laser the echo is induced in one ion species and with a third, "scrambler" pulse of a second laser another species is excited. These scrambler excitations lead to a dephasing and thus to an echo attenuation which depends on the strength, frequency, and time of the scrambler pulse. The spectral sensitivity of the echo attenuation is used for a spectroscopic technique: "photon-echo attenuation spectroscopy." As a function of the delay time

{t}_{s}

between the scrambler pulse and the onset of the two-pulse echo sequence the attenuation shows a very specific behavior dictated by the excitation-induced frequency shifts (EFS's). For

{t}_{s}

between the two echo-inducing pulses the echo intensity is partially regained by the "dephasing-rephasing balancing" of the reversible EFS's. For the theoretical description a stochastic model is introduced and the dephasing by excitation-induced lattice vibrations and by EFS's are analyzed in detail. The present results are discussed in the light of previous experimental and theoretical investigations.