Two‐Photon Excitation to the High‐Lying Triplet State of F Color Centers in LiF Crystals

Ter-Mikirtychev, Valerii V.; Tsuboi, Taijū

doi:10.1002/pssb.2221900203

Cited by 13 publications

(4 citation statements)

References 7 publications

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“…Recent progress in the technology of LiF crystals with CCs resulted in the development of room temperature stable CC lasers tunable over a broad near-IR spectral range (see [4][5][6] and references herein). Two photon excitation of F 2 and F + 3 CC has been demonstrated in [7,8]. Here we present the first demonstration of two-photon induced fluorescence of F − 2 color centers in LiF crystal under 1.906 µm excitation.…”

Section: Introductionmentioning

confidence: 87%

Two-photon absorption of F₂ ^- color centers in LiF crystal at 1906 nm

et al. 2004

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We report room-temperature two-photon induced fluorescence of the F − 2 color centers in LiF crystal in the ∼ 960 − 1300 nm spectral range. The fluorescence spectra and kinetics were measured using the first (1.906 µm) and second harmonics (0.953 µm) of a H 2 -Raman Shifted single frequency Nd:YAG laser. The fluorescence spectra and kinetics under two-photon (1.906 µm) and one-photon (0.953 µm) excitation were identical. A nonlinear dependence of the fluorescence intensity versus excitation energy of 1.906 µm radiation was demonstrated. The two-photon absorption cross section of F − 2 color center was measured to be (0.9 ± 0.4) × 10 −49 cm 4 sec at 1.906 µm. Intensities of the anti-Stokes fluorescence versus pulse energy of 1.906 µm radiation (solid line shows quadratic dependence)

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Section: Introductionmentioning

confidence: 87%

Two-photon absorption of F₂ ^- color centers in LiF crystal at 1906 nm

et al. 2004

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“…The ratio β 2 /β 1 = 4.4 found contradicts data given in [4], where a quantum yield equal to unity is indicated for both types of color centers (F 2 and F 3 + ). In the literature, measurement results are presented suggesting small energy separations between the excited singlet and triplet states for F 3 + centers, and substantial probabilities for transition of the centers from this triplet state to the excited singlet state [8]. If we assume that the relative positions of the potential energy curves for the triplet and singlet states given in [8] correspond to reality, then the probability of nonradiative transitions between them should be significant.…”

mentioning

confidence: 95%

“…In the literature, measurement results are presented suggesting small energy separations between the excited singlet and triplet states for F 3 + centers, and substantial probabilities for transition of the centers from this triplet state to the excited singlet state [8]. If we assume that the relative positions of the potential energy curves for the triplet and singlet states given in [8] correspond to reality, then the probability of nonradiative transitions between them should be significant. In such a situation, the photoluminescence quantum yield for transitions between singlet levels of the F 3 + center can be significantly less than unity.…”

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Luminescence excitation spectra and characteristics of luminescence centers with overlapping absorption bands

2008

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535.37+548.4For an ensemble of different types of luminescence centers with overlapping absorption bands, with no restrictions on the optical densities, we have obtained relations describing the luminescence excitation spectra for each type of center. We consider transformations of the relations in some limiting cases. We suggest a procedure for using the equations obtained to determine the characteristics of the luminescence centers. Some of these procedures have been experimentally implemented in study of intrinsic radiation color centers in lithium fluoride crystals. We have determined the ratios of the luminescence quantum yields for F 2 and F 3 + color centers, and we have observed that a major role is played by nonradiative transitions in deactivation of the first excited singlet state of F 3 + centers.Key words: luminescence excitation spectrum, equation for the excitation spectrum, luminescence centers with overlapping absorption bands, methods for determining characteristics of luminescence centers.Introduction. Methods based on absorption and emission of electromagnetic radiation are widely used in scientific practice, for example, for investigation of the structure of matter, intramolecular and intermolecular interactions, impurity and intrinsic structural defects in solids. Such methods are the basis for sensitive methods for determining the constituent composition of different materials. Many monographs present reviews of the basic characteristic features of luminescence and the possibilities for using them to solve scientific and practical problems (see, for example, [1,2]).Measurements of the photoluminescence (PL) or photoluminescence excitation spectra and practical use of such measurements tend to be done for samples with optical density less than unity. When this condition is not met, the excitation spectrum does not correspond to the absorption spectrum; there is no proportionality between the photoluminescence intensity and the absorption coefficient, i.e., the concentration of the component. The situation is even more complicated if the absorption spectra of several luminescence centers overlap in this case.Overlap of the absorption spectra for several centers is encountered rather frequently in the studied samples. It does not always seem possible to decrease the overall optical density of the sample down to a value much less than unity. For example, when impurity and/or intrinsic defects (arising as a result of technological operations or other external factors) are studied in a solid, samples must be studied containing all existing luminescence centers, each characterized by their own spectra, including overlapping spectra, and their own absorption values. Technological operations in the sample can be carried out at small depths (on the order of a few micrometers), and in this case several types of luminescence centers are created with overlapping absorption spectra and an overall optical density on the order of a few units (see, for example, [3]). In such cases, we need to know the conne...

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