Physical review. B, Condensed matter
Photon-echo attenuation in rare-earth-ion-doped crystals
Stefan B. Altner, G. Zumofen, Urs P. Wild, Masaharu Mitsunaga
Abstract
We study the optical properties of rare-earth-ion-doped inorganic crystals with an emphasis on the dependence of two-pulse photon echoes on the excitation density in the system. The experimental investigations concentrate on ${\mathrm{Pr}}^{3+}$:${\mathrm{Nd}}^{3+}$:${\mathrm{Eu}}^{3+}$ codoped ${\mathrm{Y}}_{2}$Si${\mathrm{O}}_{5}$ and YAl${\mathrm{O}}_{3}$ crystals at low temperatures. With two pulses of one laser the echo is induced in one ion species and with a third, "scrambler" pulse of a second laser another species is excited. These scrambler excitations lead to a dephasing and thus to an echo attenuation which depends on the strength, frequency, and time of the scrambler pulse. The spectral sensitivity of the echo attenuation is used for a spectroscopic technique: "photon-echo attenuation spectroscopy." As a function of the delay time ${t}_{s}$ between the scrambler pulse and the onset of the two-pulse echo sequence the attenuation shows a very specific behavior dictated by the excitation-induced frequency shifts (EFS's). For ${t}_{s}$ between the two echo-inducing pulses the echo intensity is partially regained by the "dephasing-rephasing balancing" of the reversible EFS's. For the theoretical description a stochastic model is introduced and the dephasing by excitation-induced lattice vibrations and by EFS's are analyzed in detail. The present results are discussed in the light of previous experimental and theoretical investigations.