Optical absorption and emission spectra have been measured for Nd-doped Y3Al5O12 ceramics obtained by a urea precipitation method. The optical properties of the ceramics are almost the same as those of single crystals grown by the Czochralski method and floating-zone method, except for a higher background absorption of 2.5–3 cm−1. The energy-level structure for Nd3+ in the Y3Al5O12 ceramics is determined for a 1-at. % Nd concentration. The induced emission cross section for the 1-at. %-Nd-doped ceramic is calculated to be 4.9×10−19 cm2, which falls in the range reported for the Nd:Y3Al5O12 single crystals. The Nd concentration dependence of the emission decay time at the 1064-nm laser wavelength was also measured, and typical concentration quenching was observed. The decay time of the 1-at. %-Nd-doped ceramic is 219 μs, which is slightly smaller than the reported values for single crystals.
Undoped and rare-earth- (Pr, Nd, Eu, and Er) doped transparent Y3Al5O12 ceramics have been prepared, and their optical spectra have been measured. It is found that absorption coefficient of the undoped ceramic Y3Al5O12 is almost independent of wavelength with 0.258 cm−1, which gives transmittance of the undoped ceramic Y3Al5O12 to be, for example, 95% for a 2-mm height. Peaks in the absorption and emission spectra of Pr:Y3Al5O12 are assigned to the transitions in 4f2 configuration. The transitions from the multiplets with total angular momentum J=0 to multiplets with even J momentum are strong as predicted by Judd–Ofelt theory. The overall and detail structure of the absorption and emission spectra of Nd:Y3Al5O12 is the same as those in a previous publication. However, the absorption coefficient at nonabsorbing wavelengths by Nd3+ is reduced from more than 1.7 to 0.25 cm−1. A simple estimation of the population inversion threshold of the Nd:Y3Al5O12 ceramic reveals that the threshold is still about 25 times larger than that of single-crystal Nd:Y3Al5O12. Peaks in the absorption and emission spectra of Er:Y3Al5O12 ceramic are assigned to the transitions in 4f11 configuration. The transition energies agree well with those reported for single-crystal Er:Y3Al5O12 and the other hosts within 30 cm−1. A Stark splitting scheme for some multiplets has been constructed. Peaks in the emission, absorption, and excitation spectra of Eu:Y3Al5O12 ceramic are assigned to the transitions in 4f6 configuration. The transition energies are in very good agreement with those of single-crystal Eu:Y3Al5O12 within 8 cm−1 for the emission peaks and 3 cm−1 for the absorption and excitation peaks. Spectral characteristics and derivation of a broad peak in the absorption spectrum at around 280 nm are discussed in some detail.
Articles you may be interested inJudd-Ofelt analysis and emission quantum efficiency of Tb-fluoride single crystals: LiTbF4 and Tb0.81Ca0.19F2.81 Magnetic susceptibilities, crystal field Stark energies, and hyperfine behavior of Sm 3 + in hexagonal single crystals of Sm ( CF 3 SO 3 ) 3 9 H 2 O A laser photolysis/time-resolved Fourier transform infrared emission study of OH (X 2 Π,v) produced in the reaction of alkyl radicals with O ( 3 P)Detailed absorption and emission spectra on TbAlO 3 are measured at room temperature and liquid-nitrogen temperature. By decomposition of the spectra, the Stark splitting scheme is established for 7 F 6 , 7 F 5 , and 5 D 4 multiplets of Tb 3ϩ ions in TbAlO 3 together with the peak energies in the Fourier transform infrared spectrum at liquid-nitrogen temperature. The multiplets are split into their maximum number of levels, which shows that the point symmetry is low for the Tb 3ϩ ion site in TbAlO 3 . An induced emission cross section is estimated using the results of decomposition at liquid-nitrogen temperature to be 3.55ϫ10 Ϫ19 cm 2 . This value is comparable to the cross sections reported for Nd:Y 3 Al 5 O 12 , which is a well known solid-state laser material. The population inversion threshold is also estimated for TbAlO 3 in comparison with Nd:Y 3 Al 5 O 12 . It is found that the threshold value for TbAlO 3 is only about three times larger than that for Nd:Y 3 Al 5 O 12 . This TbAlO 3 may have the potential to be a laser material with a visible wavelength at least at low temperature.
Optical spectra are measured for transparent and colorless TbAlO3 single crystals grown by the Czochralski method in a reducing atmosphere, although those grown in an inert atmosphere show blackbody color due to broadband absorption of Tb4+ ions. This is a report on strong Tb3+ emission spectrum at room temperature of aluminates and relevant crystals which contain the Tb ion as a stoichiometric agent. All fine structures in absorption and emission spectra can be assigned to the intra-4f transitions of Tb3+ ions. Similar concentration quenching is observed in TbxGd1−xAlO3 system to that in the Nd:YAG crystals; however, the quenching is found to be very small compared with that of the Nd:YAG. An order estimate of the induced emission cross section for the strongest emission line is calculated to be about 6×10−21 cm2.
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