Physical review. B, Condensed matter

Accumulated photon echo in neodymium-doped disordered yttrium fluoride crystals

Keith W. Ver Steeg, Alexander Ya. Karasik, Roger J. Reeves, Tasoltan T. Basiev, Richard C. Powell

Published Mar 1, 1995• 8 citations

Abstract

Accumulated photon echoes were used to measure the dephasing time (${\mathit{T}}_{2}$) of the $^{4}$${\mathit{I}}_{9/2}$${\ensuremath{\rightarrow}}^{4}$${\mathit{G}}_{5/2}$${,}^{2}$${\mathit{G}}_{7/2}$ transition of ${\mathrm{Nd}}^{3+}$ in highly disordered ${\mathrm{CaF}}_{2}$-${\mathrm{YF}}_{3}$ crystals. ${\mathit{T}}_{2}$ decreased from subnanosecond values for excitation of low-lying Stark levels to subpicosecond values for excitation of high-lying levels. From 9--100 K the measured temperature dependence of the homogeneous linewidth is described by a resonant single-phonon absorption process.

DOI: 10.1103/physrevb.51.6085

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Photon echoes of terbium in lithium yttrium fluoride

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It is important to compare dephasing mechanisms for ordered and disordered systems with a small and large inhomogeneous line broadening, respectively. We studied dephasing processes in crystals with Nd3+ ions by using the accumulated photon echo (APE) technique. Ordered (CaF2) and disordered (CaF2–YF3) crystals were chosen for investigations.

May 8, 19940 citations

Measurement of optical homogeneous linewidths in a glass with picosecond accumulated photon echoes

Robert M. Shelby

Picosecond accumulated photon echoes have been used to study optical dephasing in the (4)I(9/2)?(2)G(7/2), (4)G(5/2) transition of Nd(3+) in silicate glass. The homogeneous width exhibited a T(2.2)temperature dependence similar to that of other rare-earth systems previously studied by fluorescence line narrowing. The wavelength dependence of the echo-decay curves shows that relaxation among crystal-field states takes place in a few picoseconds.

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Physical review. B, Condensed matter

Accumulated photon echo in neodymium-doped disordered yttrium fluoride crystals

Keith W. Ver Steeg, Alexander Ya. Karasik, Roger J. Reeves, Tasoltan T. Basiev, Richard C. Powell

Published Mar 1, 1995• 8 citations

Publisher

Abstract

Accumulated photon echoes were used to measure the dephasing time (

{\mathit{T}}_{2}

) of the

^{4}$${\mathit{I}}_{9/2}$${\ensuremath{\rightarrow}}^{4}$${\mathit{G}}_{5/2}$${,}^{2}$${\mathit{G}}_{7/2}

transition of

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

in highly disordered

{\mathrm{CaF}}_{2}

{\mathrm{YF}}_{3}

crystals.

{\mathit{T}}_{2}

decreased from subnanosecond values for excitation of low-lying Stark levels to subpicosecond values for excitation of high-lying levels. From 9--100 K the measured temperature dependence of the homogeneous linewidth is described by a resonant single-phonon absorption process.

DOI: 10.1103/physrevb.51.6085

Related papers

Optical echo spectroscopy and phase relaxation of Nd3+ ions in CaF2 crystals

Tasoltan T. Basiev, Alexander Ya. Karasik, Vladimir Fedorov +1 more

Accumulated photon echoes have been used to investigate the mechanisms of optical dephasing in CaF2 crystals activated by Nd3+ ions. Tunable picosecond laser radiation, which permits the selective excitation of various Nd3+ optical centers in the 4 I 9/2→4 G 5/2, 2 G 7/2 transition, is used. The optical phase relaxation times measured at temperatures from 9 to 50 K permit determination of the homogeneous widths of the transitions between the low-lying 4 I 9/2 Stark level and three excited 4 G 5/2, 2 G 7/2 levels, and calculation of the constants of the inter-Stark relaxation transitions in the ground and excited multiplets for the rhombic N and M Nd3+ centers in CaF2 crystals. An analysis of the temperature dependence of the homogeneous linewidth of the transitions between low-lying Stark levels of the ground and excited states shows that the mechanism of optical dephasing in the crystals investigated is described well by direct relaxation processes with resonant inter-Stark absorption of one phonon in the ground and excited states. At T=9 K, the homogeneous linewidth Γh in CaF2 crystals is almost an order of magnitude smaller than Γh in disordered CaF2-YF3 crystals. This difference can be attributed to the significantly greater spectral phonon density of states in disordered crystals.Accumulated photon echoes have been used to investigate the mechanisms of optical dephasing in CaF2 crystals activated by Nd3+ ions. Tunable picosecond laser radiation, which permits the selective excitation of various Nd3+ optical centers in the 4 I 9/2→4 G 5/2, 2 G 7/2 transition, is used. The optical phase relaxation times measured at temperatures from 9 to 50 K permit determination of the homogeneous widths of the transitions between the low-lying 4 I 9/2 Stark level and three excited 4 G 5/2, 2 G 7/2 levels, and calculation of the constants of the inter-Stark relaxation transitions in the ground and excited multiplets for the rhombic N and M Nd3+ centers in CaF2 crystals. An analysis of the temperature dependence of the homogeneous linewidth of the transitions between low-lying Stark levels of the ground and excited states shows that the mechanism of optical dephasing in the crystals investigated is described well by direct relaxation processes with resonant inter-Stark absorption of one phonon in the ground and excited states. At T=9 K, the homogeneous linewidth Γh in CaF2 crystals is almost an order of magnitude smaller than Γh in disordered CaF2-YF3 crystals. This difference can be attributed to the significantly greater spectral phonon density of states in disordered crystals.

Journal of Experimental and Theoretical PhysicsJan 1, 199817 citations

Stark-level one-phonon dephasing process of Nd3+ -doped silicate glass fiber studied with accumulated photon echoes

Ryuzi Yano, Naoshi Uesugi

Measurements of the homogeneous width of the $^{4}$ ${\mathrm{G}}_{5\mathrm{/}2}$ , $^{2}$ ${\mathrm{G}}_{7\mathrm{/}2}$ ${\mathrm{\ensuremath{-}}}^{4}$ ${\mathrm{I}}_{9\mathrm{/}2}$ transition of ${\mathrm{Nd}}^{3+}$ in a silicate glass fiber at low temperatures by the technique of accumulated photon echoes show that the dephasing processes are one-phonon processes between the Stark levels of ${\mathrm{Nd}}^{3+}$ . These dephasing processes differ from the commonly observed processes of rare-earth ion-doped glasses: the local-configurational-change-induced dephasing process and the Raman process with low-frequency modes. The densely distributed Stark levels of the $^{4}$ ${\mathrm{G}}_{5\mathrm{/}2}$ and $^{2}$ ${\mathrm{G}}_{7\mathrm{/}2}$ states are responsible for one-phonon processes. The transition-wavelength dependences of the homogeneous widths ${\mathrm{\ensuremath{\Gamma}}}_{\mathrm{h}}$ (4.2 K) and ${\mathrm{\ensuremath{\Gamma}}}_{\mathrm{h}}$ (T\ensuremath{\rightarrow}0) are explained by using the one-phonon process model.Measurements of the homogeneous width of the $^{4}$ ${\mathrm{G}}_{5\mathrm{/}2}$ , $^{2}$ ${\mathrm{G}}_{7\mathrm{/}2}$ ${\mathrm{\ensuremath{-}}}^{4}$ ${\mathrm{I}}_{9\mathrm{/}2}$ transition of ${\mathrm{Nd}}^{3+}$ in a silicate glass fiber at low temperatures by the technique of accumulated photon echoes show that the dephasing processes are one-phonon processes between the Stark levels of ${\mathrm{Nd}}^{3+}$ . These dephasing processes differ from the commonly observed processes of rare-earth ion-doped glasses: the local-configurational-change-induced dephasing process and the Raman process with low-frequency modes. The densely distributed Stark levels of the $^{4}$ ${\mathrm{G}}_{5\mathrm{/}2}$ and $^{2}$ ${\mathrm{G}}_{7\mathrm{/}2}$ states are responsible for one-phonon processes. The transition-wavelength dependences of the homogeneous widths ${\mathrm{\ensuremath{\Gamma}}}_{\mathrm{h}}$ (4.2 K) and ${\mathrm{\ensuremath{\Gamma}}}_{\mathrm{h}}$ (T\ensuremath{\rightarrow}0) are explained by using the one-phonon process model.

Physical review. B, Condensed matterMar 1, 19976 citations

Photon echoes of terbium in lithium yttrium fluoride

P. Darejeh

The photon echo experiment is a method of measuring the homogeneous dephasing time (T2) from which the homogeneous linewidth of an optical transition can be calculated.In this thesis, the theories of linewidths of transitions and of the development of a photon echo are presented.Also discussed is the experimental setup by which the first photon echoes in the rare-earth terbium were observed and measured.The decays of echo intensity with laser pulse separation at the externally applied fields of 45 KG and 25 KG were plotted and from these plots a homogeneous dephasing time of HO nanoseconds was calculated.Data at 15 KG were taken, but because of the non-exponential behavior of the decay, Tj was not calculated.At 0 KG, no echo was observed, implying a decrease of the dephasing time below 15 KG.The photon echo experiment is a method of measuring the homogeneous dephasing time (T2) from which the homogeneous linewidth of an optical transition can be calculated.In this thesis, the theories of linewidths of transitions and of the development of a photon echo are presented.Also discussed is the experimental setup by which the first photon echoes in the rare-earth terbium were observed and measured.The decays of echo intensity with laser pulse separation at the externally applied fields of 45 KG and 25 KG were plotted and from these plots a homogeneous dephasing time of HO nanoseconds was calculated.Data at 15 KG were taken, but because of the non-exponential behavior of the decay, Tj was not calculated.At 0 KG, no echo was observed, implying a decrease of the dephasing time below 15 KG.

Jan 1, 19830 citations

Anisotropic Optical-Response of Eu-doped Yttrium Orthosilicate

Huimin Liu, M. L. Santiago, Weiyi Jia +1 more

Eu-doped yttrium orthosilicate (Eu(3+) : Y2SiO5) had been a subject being investigated for coherent time-domain optical memory and information processing applications since its ultraslow optical dephasing was discovered several years ago. In this crystal the weakly allowed (7)F0 - (5)D0 transition of europium ions exhibits a sufficient long dephasing time and no spectral difli.usion on a time scale of several hours at low temperature, thus an information pattern or data can be stored as a population grating in the ground state hyperfine levels. On the other hand, the study on photon-echo relaxation shows that the dephasing time T2 of Eu (3+) and other rare-earth ions doped YAG, YAlO3 strongly depends on the intensity of the excitation pulses. In Eu (3+) :YAlO3, an exponential decay of photon-echo with T2 = 53 microseconds if the excitation pulses are weak (5 vJ/pulse) was observed. However, when the excitation pulses are strong (80 pJ/pulse) they observed a much shortened T2 with a highly nonexponential decay pattern. The conclusion they derived is that the intensity-dependent dephasing rate effects are quite general, and it depends on how much the excitation intensity varies. In this paper we use transient grating formation technique showing that a temporal lattice distortion may only occur along crystal c axis, caused by EU (3+) excitation. At high excitation level the produced exciton in conduction band may also couple to the dynamical lattice relaxation process, giving rise to an apparently much shortened dephasing time.Eu-doped yttrium orthosilicate (Eu(3+) : Y2SiO5) had been a subject being investigated for coherent time-domain optical memory and information processing applications since its ultraslow optical dephasing was discovered several years ago. In this crystal the weakly allowed (7)F0 - (5)D0 transition of europium ions exhibits a sufficient long dephasing time and no spectral difli.usion on a time scale of several hours at low temperature, thus an information pattern or data can be stored as a population grating in the ground state hyperfine levels. On the other hand, the study on photon-echo relaxation shows that the dephasing time T2 of Eu (3+) and other rare-earth ions doped YAG, YAlO3 strongly depends on the intensity of the excitation pulses. In Eu (3+) :YAlO3, an exponential decay of photon-echo with T2 = 53 microseconds if the excitation pulses are weak (5 vJ/pulse) was observed. However, when the excitation pulses are strong (80 pJ/pulse) they observed a much shortened T2 with a highly nonexponential decay pattern. The conclusion they derived is that the intensity-dependent dephasing rate effects are quite general, and it depends on how much the excitation intensity varies. In this paper we use transient grating formation technique showing that a temporal lattice distortion may only occur along crystal c axis, caused by EU (3+) excitation. At high excitation level the produced exciton in conduction band may also couple to the dynamical lattice relaxation process, giving rise to an apparently much shortened dephasing time.

NASA University Research Centers Technical Advances in Aeronautics, Space Sciences and Technology, Earth Systems Sciences, Global Hydrology, and EducationFeb 22, 19980 citations

Picosecond photon-echo spectroscopy in ordered and disordered fluoride crystals doped with Nd3+ ions

Keith W. Ver Steeg, Roger J. Reeves, Vladimir Fedorov +3 more

May 8, 19940 citations

Measurement of optical homogeneous linewidths in a glass with picosecond accumulated photon echoes

Robert M. Shelby

Optics LettersFeb 1, 198366 citations

Accumulated photon echoes were used to measure the dephasing time (

{\mathit{T}}_{2}

) of the

^{4}$${\mathit{I}}_{9/2}$${\ensuremath{\rightarrow}}^{4}$${\mathit{G}}_{5/2}$${,}^{2}$${\mathit{G}}_{7/2}

transition of

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

in highly disordered

{\mathrm{CaF}}_{2}

{\mathrm{YF}}_{3}

crystals.

{\mathit{T}}_{2}

Measurements of the homogeneous width of the

^{4}

{\mathrm{G}}_{5\mathrm{/}2}

^{2}

{\mathrm{G}}_{7\mathrm{/}2}

${\mathrm{\ensuremath{-}}}^{4}$

{\mathrm{I}}_{9\mathrm{/}2}

transition of

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

in a silicate glass fiber at low temperatures by the technique of accumulated photon echoes show that the dephasing processes are one-phonon processes between the Stark levels of

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

. These dephasing processes differ from the commonly observed processes of rare-earth ion-doped glasses: the local-configurational-change-induced dephasing process and the Raman process with low-frequency modes. The densely distributed Stark levels of the

^{4}

{\mathrm{G}}_{5\mathrm{/}2}

and

^{2}

{\mathrm{G}}_{7\mathrm{/}2}

states are responsible for one-phonon processes. The transition-wavelength dependences of the homogeneous widths ${\mathrm{\ensuremath{\Gamma}}}_{\mathrm{h}}$ (4.2 K) and ${\mathrm{\ensuremath{\Gamma}}}_{\mathrm{h}}$ (T\ensuremath{\rightarrow}0) are explained by using the one-phonon process model.