Room Temperature Hole-Burning in Sm2+-doped Borate Glasses

Recently, the interests in optical memory based on persistent spectral hole burning (PSHB) are increased because of its possibility of the application to high density optical memory. PSHB was observed for an organic dye doped in polymer and rear earth or transition metal doped in inorganic crystal or glasses up to now. Since PSHB was observed by two Russian groups (Gorokhovskii et al. and Kharlamov et al.) for free base phthalocyanine in a n-octane Shpol'skii matrix1 and for perylene and 9-aminoacridine molecules in glassy ethanol matrix2, PSHB materials are studied primarily for the polymer doped with an organic dye. But such materials can make hole only at very low temperature. Room temperature PSHB phenomena were observed on Sm2+ doped fluoride crystals3-5 and glasses6 recently, however these materials' Гih(inhomogeneous line width)/Гh(homogeneous line width)'s which are the parameters of data multiplicity in PSHB optical memory are an order of unity. For the application of PSHB materials to optical memory, high operating temperature, high Гih/Гh, and rapid reaction rate are wanted. Glass has a superiority on the view point of optical memory application because of its broad inhomogeneous line width and productivity. Our group has discovered room temperature PSHB for Sm2+ in borate glass systems whose Гih/Гh is 24.7 PSHB for rear earth metal in glass matrix has not been studied seriously, yet. It is thought that the study of the relationship between the optical hole and glass structure is necessary.