Spectroscopy is a branch of physics which deals with the study of interaction of electromagnetic radiation with matter. The interaction of electromagnetic radiation with matter can cause redirection of the radiation and/or transitions between the energy levels of the atoms or molecules. This technique is one of the most powerful tool to investigate various physical and chemical properties of the matter in the modern science and technology. The applications of spectroscopy not only confined to physics and chemistry but also it stretches to entire fields like biology, communication, defence, forensic, geology, industry and medicine.In recent years, spectroscopic studies of trivalent lanthanide (Ln3+) ion based materials are attracting much attention due to their potential technological applications in optical devices such as solid state lasers, optical fiber amplifiers, light converters, optical storage materials, phosphors and sensors, spectral hole burning high density memories, accousto-optic modifiers and planar wave guides and so on.