Optical spectra of undoped and rare‐earth‐(=Pr, Nd, Eu, and Er) doped transparent ceramic Y₃Al₅O₁₂

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.