This book brings together more than 100 specialists from around the world to examine the status and emerging trends in the field of rare-earth-doped materials. These materials are used and/or are potential candidates for applications as lasers, light-emitting diodes, phosphors, displays and other photonic applications. Progress in growth, doping methods, characterization and device applications are reviewed. Topics include: rare-earth doping in nitrides; rare-earth doping in silicon-related materials; mechanisms and laser materials and phosphors and scintillators.