Physical Review Letters

Observation of the Optical Analog of the Mössbauer Effect in Ruby

A. Szabó

Published Aug 9, 1971• 130 citations

Abstract

Laser-induced fluorescence line narrowing of the ruby ${R}_{1}$ Zeeman spectra at 693.4 nm is reported using a continuous, stable, single-frequency ruby laser for resonant excitation. A resolution in excess of ${10}^{7}$ corresponding to a linewidth of \ensuremath{\sim} 30 MHz has been achieved. The linewidths are anisotropic with respect to the relative magnetic-field-crystal-axis orientation and, at low Cr concentrations, are expected to be determined by Cr-Al superhyperfine interactions.

DOI: 10.1103/physrevlett.27.323

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Physical Review Letters

Observation of the Optical Analog of the Mössbauer Effect in Ruby

A. Szabó

Published Aug 9, 1971• 130 citations

Publisher

Abstract

Laser-induced fluorescence line narrowing of the ruby

{R}_{1}

Zeeman spectra at 693.4 nm is reported using a continuous, stable, single-frequency ruby laser for resonant excitation. A resolution in excess of

{10}^{7}

corresponding to a linewidth of \ensuremath{\sim} 30 MHz has been achieved. The linewidths are anisotropic with respect to the relative magnetic-field-crystal-axis orientation and, at low Cr concentrations, are expected to be determined by Cr-Al superhyperfine interactions.

DOI: 10.1103/physrevlett.27.323

Related papers

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Optical hole burning in ruby

Paul E. Jessop, T. Muramoto, A. Szabó

We report experimental and theoretical studies of optical hole burning in the inhomogeneous ${R}_{1}$ line of ruby at low temperatures. Both Stark-shifting and pump-probe techniques using narrow-band single-frequency lasers were employed. In addition to the observation of narrow holes, we have found that a large (up to 70%) decrease in absorption occurs outside the hole and that the relative size of this decrease is constant over the entire inhomogeneous line. This effect is ascribed to fast resonant cross-spin relaxation in the ground-state levels which drives all spins within the optically pumped volume to a common spin temperature. A theoretical model is formulated which describes the power-broadened hole shapes as well as the off-resonance decrease in the absorption coefficient. Fair agreement with experiment is obtained for the case of a magnetic field applied along the $c$ axis; however, sizable deviations from the theory are seen for zero field. We conclude that further studies are needed to elucidate the nature of the Al superhyperfine-broadening mechanism. An upper limit of 1200 nm is deduced for the size of macroscopically broadened regions in ruby.We report experimental and theoretical studies of optical hole burning in the inhomogeneous ${R}_{1}$ line of ruby at low temperatures. Both Stark-shifting and pump-probe techniques using narrow-band single-frequency lasers were employed. In addition to the observation of narrow holes, we have found that a large (up to 70%) decrease in absorption occurs outside the hole and that the relative size of this decrease is constant over the entire inhomogeneous line. This effect is ascribed to fast resonant cross-spin relaxation in the ground-state levels which drives all spins within the optically pumped volume to a common spin temperature. A theoretical model is formulated which describes the power-broadened hole shapes as well as the off-resonance decrease in the absorption coefficient. Fair agreement with experiment is obtained for the case of a magnetic field applied along the $c$ axis; however, sizable deviations from the theory are seen for zero field. We conclude that further studies are needed to elucidate the nature of the Al superhyperfine-broadening mechanism. An upper limit of 1200 nm is deduced for the size of macroscopically broadened regions in ruby.

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Sharp resonances in optical excitation of ruby by laser pulses are observed as Zeeman sublevels anticross in an external magnetic field. For the ${R}_{1}$ optical line of ruby $(694.3\phantom{\rule{0.3em}{0ex}}\mathrm{nm})$ excitation drops when the external magnetic field strength approaches $4.14\phantom{\rule{0.3em}{0ex}}\mathrm{kG}$ while for the ${R}_{2}$ line $(692.9\phantom{\rule{0.3em}{0ex}}\mathrm{nm})$ it increases in $4.14$ and $2.07\phantom{\rule{0.3em}{0ex}}\mathrm{kG}$ fields. A simple theoretical description of the observed effects on the basis of level mixing explains both situations.Sharp resonances in optical excitation of ruby by laser pulses are observed as Zeeman sublevels anticross in an external magnetic field. For the ${R}_{1}$ optical line of ruby $(694.3\phantom{\rule{0.3em}{0ex}}\mathrm{nm})$ excitation drops when the external magnetic field strength approaches $4.14\phantom{\rule{0.3em}{0ex}}\mathrm{kG}$ while for the ${R}_{2}$ line $(692.9\phantom{\rule{0.3em}{0ex}}\mathrm{nm})$ it increases in $4.14$ and $2.07\phantom{\rule{0.3em}{0ex}}\mathrm{kG}$ fields. A simple theoretical description of the observed effects on the basis of level mixing explains both situations.

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Fluorescence-line-narrowing and time-resolved studies have been conducted in ruby crystals and powders, in concentrations varying from 0.025 to 0.9 at.%. The resonance fluorescence component of the ${R}_{1}$ line at low temperatures is observed to increase dramatically as the laser is tuned from line center toward the low-energy wing of the inhomogeneously broadened absorption. This is presumed to indicate the presence of weakly coupled pairs in the wings of the line. Intraline and interline (${R}_{1}\ensuremath{\rightarrow}{N}_{1,2}$) energy transfer have also been studied, and an elaboration of earlier work is given. Time-resolved selective-excitation scans have revealed numerous channels in the vicinity of the $R$ lines by which the different pairs can be directly excited. These are assumed to be Cr ions near enough to a pair to be in a highly perturbed environment. Various experimental results are shown to be consistent with a model of rapid transfer between resonant Cr ions which feeds the pairs via a weak, nonresonant coupling to these perturbed ions. Macroscopic strain broadening is also shown to be favored over microscopic broadening, and the implications for Anderson localization in ruby are discussed.Fluorescence-line-narrowing and time-resolved studies have been conducted in ruby crystals and powders, in concentrations varying from 0.025 to 0.9 at.%. The resonance fluorescence component of the ${R}_{1}$ line at low temperatures is observed to increase dramatically as the laser is tuned from line center toward the low-energy wing of the inhomogeneously broadened absorption. This is presumed to indicate the presence of weakly coupled pairs in the wings of the line. Intraline and interline (${R}_{1}\ensuremath{\rightarrow}{N}_{1,2}$) energy transfer have also been studied, and an elaboration of earlier work is given. Time-resolved selective-excitation scans have revealed numerous channels in the vicinity of the $R$ lines by which the different pairs can be directly excited. These are assumed to be Cr ions near enough to a pair to be in a highly perturbed environment. Various experimental results are shown to be consistent with a model of rapid transfer between resonant Cr ions which feeds the pairs via a weak, nonresonant coupling to these perturbed ions. Macroscopic strain broadening is also shown to be favored over microscopic broadening, and the implications for Anderson localization in ruby are discussed.

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Investigation of Zeeman second-order effects in Pr3+:LaCl3using the fluorescence-line-narrowing technique

Nicole Pelletier-Allard, R. Pelletier

A technique involving the laser-induced narrowing of a fluorescence line is used to obtain high-resolution spectra of Pr3+:LaCl3. The second-order effects caused by Zeeman and nuclear interactions are systematically investigated in the 3H4E2 to or from 1D2A1 transition. A non-zero perpendicular Zeeman splitting of the ground level, proportional to the square of the magnetic field, is measured and interpreted as being caused by the perturbation by the four upper Stark levels belonging to the 3H4 multiplet. The variation of the number and of the relative intensities of the hyperfine lines is demonstrated to be closely related to the angle between the external magnetic field direction and the crystal axis. It is unambiguously attributed to an angular dependence, with regard to the magnetic field direction, of the hyperfine states of the excited level. The importance of the effect, caused by a very distant perturbing level, is shown to be a result of the quasidegeneracy of the mu =0 excited level.A technique involving the laser-induced narrowing of a fluorescence line is used to obtain high-resolution spectra of Pr3+:LaCl3. The second-order effects caused by Zeeman and nuclear interactions are systematically investigated in the 3H4E2 to or from 1D2A1 transition. A non-zero perpendicular Zeeman splitting of the ground level, proportional to the square of the magnetic field, is measured and interpreted as being caused by the perturbation by the four upper Stark levels belonging to the 3H4 multiplet. The variation of the number and of the relative intensities of the hyperfine lines is demonstrated to be closely related to the angle between the external magnetic field direction and the crystal axis. It is unambiguously attributed to an angular dependence, with regard to the magnetic field direction, of the hyperfine states of the excited level. The importance of the effect, caused by a very distant perturbing level, is shown to be a result of the quasidegeneracy of the mu =0 excited level.

Journal of Physics C Solid State PhysicsNov 14, 19794 citations

Laser-induced fluorescence line narrowing of the ruby

{R}_{1}

Zeeman spectra at 693.4 nm is reported using a continuous, stable, single-frequency ruby laser for resonant excitation. A resolution in excess of

{10}^{7}

Using resonance ruby-laser excitation, narrowing of the ruby

{R}_{1}

fluorescence line to width 0.002 ${\mathrm{cm}}^{\ensuremath{-}1}$ at 4.2\ifmmode^\circ\else\textdegree\fi{}K is observed. Absence of spectral diffusion indicates that a short-range interaction rather than earlier postulated multipolar interactions is responsible for energy transfer in concentrated ruby.

We report experimental and theoretical studies of optical hole burning in the inhomogeneous

{R}_{1}

line of ruby at low temperatures. Both Stark-shifting and pump-probe techniques using narrow-band single-frequency lasers were employed. In addition to the observation of narrow holes, we have found that a large (up to 70%) decrease in absorption occurs outside the hole and that the relative size of this decrease is constant over the entire inhomogeneous line. This effect is ascribed to fast resonant cross-spin relaxation in the ground-state levels which drives all spins within the optically pumped volume to a common spin temperature. A theoretical model is formulated which describes the power-broadened hole shapes as well as the off-resonance decrease in the absorption coefficient. Fair agreement with experiment is obtained for the case of a magnetic field applied along the

c

axis; however, sizable deviations from the theory are seen for zero field. We conclude that further studies are needed to elucidate the nature of the Al superhyperfine-broadening mechanism. An upper limit of 1200 nm is deduced for the size of macroscopically broadened regions in ruby.

Sharp resonances in optical excitation of ruby by laser pulses are observed as Zeeman sublevels anticross in an external magnetic field. For the

{R}_{1}

optical line of ruby

(694.3\phantom{\rule{0.3em}{0ex}}\mathrm{nm})

excitation drops when the external magnetic field strength approaches

4.14\phantom{\rule{0.3em}{0ex}}\mathrm{kG}

while for the

{R}_{2}

line

(692.9\phantom{\rule{0.3em}{0ex}}\mathrm{nm})

it increases in

4.14

and

2.07\phantom{\rule{0.3em}{0ex}}\mathrm{kG}

fields. A simple theoretical description of the observed effects on the basis of level mixing explains both situations.

Fluorescence-line-narrowing and time-resolved studies have been conducted in ruby crystals and powders, in concentrations varying from 0.025 to 0.9 at.%. The resonance fluorescence component of the

{R}_{1}

line at low temperatures is observed to increase dramatically as the laser is tuned from line center toward the low-energy wing of the inhomogeneously broadened absorption. This is presumed to indicate the presence of weakly coupled pairs in the wings of the line. Intraline and interline (${R}_{1}\ensuremath{\rightarrow}{N}_{1,2}$) energy transfer have also been studied, and an elaboration of earlier work is given. Time-resolved selective-excitation scans have revealed numerous channels in the vicinity of the

R

lines by which the different pairs can be directly excited. These are assumed to be Cr ions near enough to a pair to be in a highly perturbed environment. Various experimental results are shown to be consistent with a model of rapid transfer between resonant Cr ions which feeds the pairs via a weak, nonresonant coupling to these perturbed ions. Macroscopic strain broadening is also shown to be favored over microscopic broadening, and the implications for Anderson localization in ruby are discussed.