Spectral holeburning and statistical fine structure of Nd3+ in silica glass

Abstract

In this paper we report the observation of spectral hole burning and static absorption fluctuations in the 4 F 3 2 - 4 I 9 2 transition of Nd 3+ in pure silica glass. The active ions are embedded in the silica glass core of an optical fiber, and FM spectroscopy is used to detect the very shallow holes burnt. The magnitude and temperature dependence of the hole width are strongly influenced by the same slowly-relaxing tunneling systems which contribute to the time-dependent specific heat seen in this glass. These measurements, together with earlier measurements of photon echoes in this system, can be compared to theories of dephasing using the well-known properties of tunneling systems in silica glass. In addition to holeburning, we also observe fluctuations of the absorption coefficient α(ω) as a function of frequency across the absorption line which reflect statistical fluctuations in the number of ions contributing to α(ω) at any particular laser frequency.