Influence of excited-statePr3+on the relaxation of thePr3+:YAlO33H4−1D2transition (original) (raw)

Spectroscopic and relaxation character of theP03−H43transition in LaF3:Pr3+measured by photon echoes

Physical Review B

The hyperfine structure and relaxation character of the terminal levels of the Pp-H4 0 (4777 A) transition in LaF:Pr + (0.03 at, %} were studied using the photon-echo technique. Using two independent nitrogen-laser pumped dye lasers we have observed modulated photon echoes for pulse separations over a-10-p,sec range. In this interval our modulated photon echoes decay in a simple exponential manner by a factor. of 10 and yield a homogeneous linewidth of 70 kHz [full width at half maximum (FWHM)]. Fourier transformation of the echo-modulation data yields directly the nuclear level splittings and their associated linewidths in the Pp and H4 states. In the Pp (H4) state the nuclear splittings are 0.73 and 1.12 MHz (8.48 and 16,68 MHz). The measurements for the nuclear level splittings and associated linewidths in the H4 state are in excellent agreement with those obtained from the optical-rf double-resonance experiments of Erickson. We find that the calculated echo modulation is a sensitive function of the relative orientation of the principal axes associated with the groundand excited-state Hamiltonians. By comparing our experimental and calculated echo-modulation patterns we are able to determine their relative orientations.

Homogeneous broadening and hyperfine structure of optical transitions inPr3+:Y2SiO5

Physical Review B, 1995

Contributions to the homogeneous linewidth of the H&(1)~'Dz(1) transition for the two crystallographic sites of Pr in Y2SiO, have been investigated using photon echoes. The effects of excitationintensity-dependent dephasing or instantaneous diffusion were systematically studied to allow accurate determination of the optical resonance widths. Homogeneous linewidths of 2.8 kHz (site 1) and 1 kHz (site 2) were measured with no applied magnetic field and with sufficiently low laser intensity to minimize the effects of instantaneous diffusion. Using the same excitation intensity, widths of 2.1 kHz (site 1) and 0.85 kHz (site 2) were obtained with an applied magnetic field of 77 G, demonstrating a significant contribution of Y nuclear-spin fluctuations to the zero-field homogeneous linewidth. Extrapolation to zero excitation intensity yielded optical resonance widths that were only slightly narrower than the measured values. Optically detected nuclear magnetic resonance measurements determined the hyperfine structure of the H& ground state for each site; the hyperfine levels of the lowest component of the 'D2 manifold for each site were determined using photon echo nuclear double resonance. The relatively large oscillator strength of 3 X 10 for a rare-earth ion, in conjunction with long dephasing times makes this material a useful candidate for demonstration of time-domain signal processing and optical data storage.

Excited-state absorption inPr3+:Y3Al5O12

Physical Review B, 1994

The optical-absorption transitions originating from the lowest 4fSd excited state of Pr'+ in Y,A1,0,z have been studied. The experimental arrangement uses a 7-ns 266-nm light pulse to populate the lowest 4fSd state, and a spatially overlapped, time-sequenced pulse from a frequency-tunable dye laser to induce transitions from that excited state. The excited-state-absorption (ESA) spectrum covering the 900-300-nm probe wavelength range is characterized by two broad peaks centered at 700 and 350 nm on a slowly rising background. The peak ESA cross section at 355 nm is (1+0.1)X10 ' cm'. The position, shape, and strength of the spectrum suggest that the terminal states of the ESA transitions are the second 4f5d state of Pr3+ and the conduction band of the host lattice. The ESA measurements have been extended to transitions from the Po and 'Di excited states of the 4f configuration of Pr + as well. The ESA cross sections at a probe wavelength of 532 nm are (8+1)X 10 ' cm' and (5.7+0.6) X 10 cm for transitions from the Po and 'D& excited states, respectively. The terminal state of ESA transitions from these two levels is the lowest 4f5d state. The strong ESA completely inhibits the potential laser action based on emission from these states in this crystal. 10 '-10 ' cm. More recently, strong ESA at a probe wavelength of 224 nm has been reported in four Pr +doped fluoride crystals: CaF2, SrF2, LiYF4, and BaY2FS. ' In Pr +LiYF4, these authors measured an ESA cross section of 2.6+0.5X10 ' cm at 224 nm which corresponds to a local emission peak characterized by an emission cross section of 2.0+0.2X10 ' cm .

Non-Markovian nature of relaxation processes and its spectroscopic manifestations

Soviet Journal of Quantum Electronics, 1976

Ab initio results for e-LiH and e-CO scattering are reported using a new numerical continuum basis in the R-matrix method. In the case of e-LiH scattering, converged 'P eigenphase sums are obtained in the static exchange approximation. In the case of e-CO scattering, converged eigenphase sums and momentum transfer cross sections are obtained at low and intermediate energies including electron exchange and nonadiabatic polarisation effects. The low-energy e-CO 'II shape-resonance parameters are calculated as a function of internuclear separation for the first time, and are found to be in excellent agreement with experiment. Evidence is also presented for the e-CO *I: shape resonance at about 20 eV. The momentum transfer cross section is in good agreement with experiment.

Resonant enhancement of two-photon transitions to the second excited 4f5d state in Pr3+:Y3Al5O12

Phys. Rev. B, 1993

The two-photon absorption cross section for transitions from the 'H4 ground-state manifold to the second excited state of the 4f5d configuration of Pr'+ in Y&A1,0,2 is observed to be enhanced by about two orders of magnitude when the excitation frequency happens to be resonant with the PJ (J =0, 1,2) and 'I6 intermediate states of the 4f configuration. The structure and line shape of the two-photon excitation spectrum spanning the 39600-46950 cm transition-energy range are entirely dominated by these resonantly enhanced transitions, while the contributions from nonresonant transitions appear as a slowly varying background beneath the strong resonance peaks. A two-photon absorption cross section as high as 4X 10 cm s is measured at the peak of the resonantly enhanced transition at 44246 cm which involves a level of the I'2 manifold as the intermediate state. The spectrally integrated cross section over that manifold is 3.3 X 10 cm .

Two-photon excitation of the lowest 4f2→4f5d near-ultraviolet transitions in Pr3+:Y3Al5O12

Phys. Rev. B, 1992

Two-photon transitions from the 'H4 ground-state manifold of the 4f' configuration to the lowest state of the 4fSd configuration of Pr in YiAlsO, t have been studied with a tunable dye laser as a function of the excitation wavelength, intensity, temperature, and focusing geometry. The two-photon excitation spectrum is vibronic in nature and covers the 555-615-nm excitation wavelength range. Both the direct nonresonant and the resonantly enhanced transitions are observed. The measured two-photonabsorption cross section varies over 3 orders of magnitude with a maximum of 1X10 " cm s at the peak of the resonantly enhanced transition at 581 nm. The parity selection rule which forbids these two-photon transitions in a free ion is relaxed by odd-parity crystal-field mixing of the wave functions, making these transitions possible. Two-photon excitation measurements are complemented by onephoton-absorption and-emission measurements.

Optical-Pumping Transients in Rubidium-87 and Application to Excited-State Disorientation Cross Sections

Physical Review, 1966

Detailed studies have been made of the light transmitted through rubidium-87 vapor during the opticalpumping process, both with and without buffer gas present. The observed transients are single exponentials with no buffer gas present, and double exponentials with buffer gas present, over a wide range of pumping intensities and relaxation times. These results are in excellent agreement with the predictions based on phenomenological equations in which nuclear spin is included and a single relaxation time is assumed. From a study of the amplitudes of the two exponential components of the optical-pumping transient, an effective cross section 0. e ff is deduced for the disorientation of rubidium-87 within the 5 Plf2 state as a result of its collision with a buffer-gas atom. It is shown that 0;gg= fTip+osf2, where o ii~i s the cross section for disorientation within the 52PJig level, and cr312 is the cross section for transfer from the 5'Pif~level to the 5'P~f2 level by means of collisions with the buffer gas. On the basis of recently measured values for o. 3f2, values are deduced for aIis. The cross sections are: o&is(Rb-He) =1.5(0 8))&10 "cm' a|is(Rb-Ne) =4 4(2.2) X10 " cm', and oIis(Rb-Ar) =3.5(1. 8) &(10 " cm'. These cross sections are deduced from a model in which the probabilities for Rb ' to relax from any hyper6ne level to any other are all equal. This model gives a better fit with the observed transients than the assumption that the electron spin only is randomized in the P~i2 state with the nuclear spin unaffected. We show that accurate relaxation-time measurements can be made by measuring the time constants associated with the double exponentials as a function of light intensity, and extrapolating them to zero light intensity. Moreover, since no shutter is required, relaxation times &10 ' sec can be easily observed.

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

Physical Review B, 1990

Photon-echo-relaxation measurements made on the 'H4-'Po transition of 0.01 at. % Pr'+:YAG (where YAG represents yttrium aluminum garnet), 'H4-'D2 transition in 0.1 at. % Pr'+:YA103, and Fo-'Do transition in 0.25 at. % Eu'+:YA103 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 Pr'+:YAG may be attributed to an instantaneous spectral diff'usion (ISD) in which the presence of excited neighboring Pr'+ 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.

4f 2 to 4f5d excited state absorption in Pr 3+ :YAlO 3

Journal of Physics: Condensed Matter, 1999

Excited-state absorption spectra, from the 3 P J-1 I 6 or 1 D 2 manifold to 4f5d levels, recorded in the 23 000-42 000 cm −1 range and calibrated in units of cross sections, are reported and discussed in the case of Pr 3+-doped YAlO 3. The 4f5d→ 4f 2 Pr 3+ emission between 30 000 and 44 000 cm −1 is then observed, showing the possibility of UV laser operation following two-step excitation pumping using near-UV-visible pump photons.