Spectral hole burning properties of rotationally localized CN- deffects in cesium halides

Abstract

Persistent spectral hole and antihole burning has been used to study the homogeneous linewidth and dynamical behavior of rotationally aligned CN- defects in cesium halides. Rotational alignment occurs by statistically associating the CN- defect to a neighboring K+ or Rb+ impurity. The resulting defect pair produces sharp background-free stretching absorption lines v1 and v2 near 2000 cm-1, corresponding to two possible orientations of the CN- electric dipole moment with respect to the neighboring alkaline-ion impurity. Measurements were performed on the v1 and v2 2nd harmonic transitions near 4000 cm-1 using a single-mode tunable color center laser. Burning polarized persistent holes into the v2 line produces equally polarized antiholes in the v1 line and vice versa, indicating that 180° CN- reorientations among the 〈111〉 pair axes are optically induced. At T<40 K, each configuration is stable due to a high rotational barrier and can be fully populated. Thermal hole refilling occurs with a sharp temperature dependence near 40 K. For dilute CN-:K+ defects in CsCl minimum homogeneous linewidths of ≈10 MHz were measured, corresponding to a dephasing time T2≈15 ns. Since the radiative lifetime T1 is in the millisecond range, fast dephasing processes are thus dominating the homogeneous broadening.