The proposal describes a three-year program to investigate the details of non-radiative relaxation in solid-state materials using comprehensive characterization of local modes and phonon modes coupling pathways and different parameters affecting these interactions. Flourescence lifetime measurements, resonance Raman scatering, off-resonant Raman scattering, up-converted hot luminescence measurements and time resolved Raman measurements will be used to assess the overall and local effects of nonradiative processes taking place in the Cr4+ impurity-doped host materials. These measurements will be able to pinpoint the major factors responsible for the relaxation, and thus lead to help develop high performance light sources and optical materials. ***
