Optical Dephasing in Inorganic Glasses

Abstract

In recent years it has become clear that the low temperature dynamical properites of glasses are quite different from those of crystals and that this has a profound effect on the relaxation behavior of ions and molecules present as dopants in glassy media [1,2]. In particular, the presence of ‘two level systems‘ (TLS) — double well potentials associated with defects in glasses with a wide range of tunneling splittings [3] — has been proposed to explain the linewidths seen in optical experiments at low temperatures. Fluorescence line narrowing [1,2] and hole burning [4,5] widths are observed corresponding to dephasing times (T₂) in the nanosecond and sub-nanosecond range, as much as four orders of magnitude faster than for the same ion or molecule in a crystal.