Cooperative optical bistability in the dimer system Cs3Y2Br9:10% Yb3+

Abstract

In single crystals of the dimer compound Cs 3 Y 2 Br 9 :10% Yb 3ϩ below 31 K, both visible ͑VIS͒ and near-infrared ͑NIR͒ luminescence intensities were found to exhibit hysteresis as a function of incident NIR intensity and temperature. The optical bistability is intrinsic to Cs 3 Y 2 Br 9 :10% Yb 3ϩ and not a result of an external feedback. Lowering the temperature to 11 K strongly enhances the all-optical switching behavior. The switching on VIS cooperative upconversion and NIR luminescence transitions occurs simultaneously and with opposite polarity reflecting the competition of both emission processes. On/Off switching ratios of up to 4.8 and 1.7 were observed for VIS and NIR luminescence intensities. Using NIR luminescence spectroscopy, differences in the internal sample temperature of up to 7 K were found between the upper and lower branches of the hystereses. A two-level density-matrix model is developed which includes ground-and excited-state interactions and shows that the intrinsic bistability due to a local field different from the external field is strongly amplified by the nonlinear cooperative upconversion process. Alternatively, a rate-equation model is presented which takes the multilevel nature of the ions into account but is more phenomenological in nature. Formally, the two models are shown to be equivalent, and they qualitatively explain all major experimental observations. It is found both theoretically and experimentally that increasing the coupling within Yb 3ϩ dimers and/or decreasing energy migration through the Yb 3ϩ lattice enhances switching and renders it easier to observe intrinsic optical bistability.

Cooperative emission study in ytterbium-doped Y2SiO5

“…Nevertheless, as indicated by the fit in both cases, the exchange coupled pairs contribution to the overall cooperative emission is at least as important as the isolated ions contribution. Since distances between ion pairs are smaller than 4 Å , namely for site I:3.395, 3.507, 3.721, 3.721, 3.791 Å ; and for site II:3.395, 3.459, 3.507, 3.623, 3.721 Å , magnetic interactions become important as observed in the case of Cs 3 Yb 2 Br 9 pairs 3.83 Å distant [8,13].…”

“…Besides YbPO 4 , other ytterbium activated hosts emit cooperative luminescence, centered around 500 nm, under infrared excitation e.g. [6][7][8].…”

Electromagnetically induced intrinsic bistability at the atomic level

“…Theoretical works have also pointed out the possibility of intrinsic OB induced by polarization effects and ion-ion interactions [2,3]. General conditions of intrinsic OB for interacting systems have been given and applied with success to magnetic bistability in the microwave range [4].…”

A Review of Heat Transfer Physics

“…In the nanoparticles studied, cooperative effects are negligible [129]. Hence, the rate equation for the two-level system shown in Figure 14(a) is …”