Inhomogeneous Broadening and Persistent Spectral Hole-Burning of Divalent Samarium Ions In Alkaline Earth Metal Halides

Abstract

Persistent spectral hole burning (PSHB) was discovered in organic molecular system in 1974[1]. Five years later, PSHB in inorganic materials was discovered in NaF by R. M. Macfarlane et al [2]. In 1985, A. Winnacker et al [3] first observed photon gated spectral hole burning in BaFCl: Sm2+ at 2K. Hole burning(HB) is useful in high resolution spectroscopy. It is also of crucial importance for the application to frequency domain optical storage. The storage density is proportional to the ratio of inhomogeneous linewidth(Γi) to the homogeneous linewidth(Γh), N(= Γi/Γh). The inhomogeneous linewidth of 5D0-TF0 transition of Sm2+ is 16GHz and the hole width is 25MHz in BaFCl at 2K[3]. For this material, the inhomogeneous linewidth changes only moderately with the temperature; On the other hand, the homogeneous linewidth increases rapidly as the temperature rises. Then, a small value of N(~2) can be estimated when HB temperature is raised to 77K. That means, it is difficult to burn a hloe in the inhomogeneous line in BaFCl:Sm2+ at 77K. To maintain a reasonable storage capacity or to study HB at a quite high temperature, a large inhomogeneous linewidth is in great request.