Optical dephasing mechanisms in Tm(3+):Y(2)Si(2)O(7).

Optical dephasing measurements are reported for Tm(3+):Y(2)Si(2)O(7) as a function of temperature and laser excitation intensity. By use of photon echoes, a coherence time of T(2) = 23 micros was measured at 1.24 K for the (3)H(6)(1) ? (3)H(4)(1) transition at 790.427 nm, corresponding to a homogeneous linewidth of 14 kHz. The relatively broad inhomogeneous linewidth of 100 GHz gives an inhomogeneous-to-homogeneous linewidth ratio of Gamma(inh)/Gammah = 7 x 10(6). This large ratio, a transition wavelength suitable for GaAlAs semiconductor lasers, and the absence of hyperfine structure hole burning make this material a good candidate for time-domain signal processing and transient optically addressed data storage.

A single-crystal neutron scattering study of lattice melting in ferroelastic [Formula: see text].

We present the results of an extensive single-crystal neutron scattering study of the ferroelastic phase transition in [Formula: see text]. This material has previously been demonstrated to undergo a continuous loss of long-range order at its ferroelastic transition, which is the phenomenon known as lattice melting. We show that our data are consistent with a special form of lattice melting where the long-range order appears to be destroyed in a two-dimensional sense, but is preserved in the third dimension.