Dana M. Calistru

Identification of the symmetry of phonon modes in CsPbCl3 in phase IV by Raman and resonance-Raman scattering

The first- and second-order Raman phonon spectra of CsPbCl3 were measured in phase IV using Raman and resonance-Raman scattering. Twelve Raman active phonons were resolved at 32, 35.5, 42, 52, 72, 90, 110, 115, 121, 189, 200.5, and 375 cm−1 and correlated to the phonon spectrum of CsPbCl3 in phase I. The highest frequency longitudinal optical mode is 375 cm−1.

Criterion for selecting phonons and local vibrations involved in the nonradiative relaxation of photoexcited Cr4+ ions in forsterite

The energy of Cr4+ local modes and the energy and dynamics of Mg2SiO4 phonon modes involved in the nonradiative relaxation of photoexcited impurity Cr4+ ions in forsterite crystal were measured. The experimental results suggest that resonance in energy between local vibrations of the impurity ion and lattice (phonon) modes of the host crystal plays a crucial role in selecting the phonons which participate in the nonradiative relaxation of the photoexcited ions in crystals.

Direct observation of second neighbor interactions for Cr4+ doped forsterite by resonance Raman scattering

Fifteen Cr4+ local modes are observed using resonance Raman scattering in a Cr:Mg 2SiO4 crystal, instead of a maximum of nine internal vibrations predicted by first neighbor interactions. The larger‐than‐predicted number of modes is explained in terms of second neighbor interactions for the Cr4+ ion. The frequency dependence of the two tetrahedral stretching modes measured at 361 and 765 cm−1 on second neighbor parameters shows a different degree of localization at the Cr 4+ site for these modes.

Role of local-phonon mode coupling in the nonradiative relaxation for designing more efficient impurity doped solid state laser crystals

Based on measurements of the dynamics of local and phonon modes in Cr:Mg2SiO4 during the nonradiative relaxation of Cr4+ laser ions, and on the phonon and local spectrum of the analog Cr4+:Ca2GeO4 laser crystal, we propose general criteria to design higher efficiency ion-doped laser crystals