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We have measured the optical dephasing time of Er(3+) transitions near 1.5 microm in the two crystallographically inequivalent sites of Y(2)SiO(5), using an external-cavity diode laser amplified by an erbium-doped fiber amplifier. Two-pulse photon echoes were observed at zero field and in magnetic fields up to 55kG, with dephasing times as long as 580 micros (corresponding to a linewidth of 550 Hz). Stimulated echoes were also measured and showed evidence of spectral diffusion during the 13-ms lifetime of the (4)I(13/2) level.

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.