We report the first observation of intrinsic optical bistability in CsCdBr 3 :1% Yb 31 and show, using site-selective spectroscopy, that only the asymmetric, strongly coupled Yb 31 ion-pair minority site gives rise to hysteresis of near-infrared and cooperative up-conversion luminescence as a function of incident laser intensity below 15 K. [S0031-9007(99)08880-8]

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Intrinsic bistability and hysteresis have been observed in the photoluminescence of bulk glass doped with Yb3+ and Tm3+ impurities at room temperature. Multiple instabilities also occur in channel waveguide lasers in this material. Consequently, local field effects exhibit more degrees of freedom than expected and have important implications for compact optical amplifiers and oscillators.

Articles you may be interested inTwo-dimensional electron gases: Theory of ultrafast dynamics of electron-phonon interactions in graphene, surfaces, and quantum wells A cluster model study of the electron-phonon interaction in magnesium diborate Pronounced electron-phonon coupling is observed for the 2 F 7/2 ↔ 2 F 5/2 4 f transitions of Yb 3ϩ doped into CsCdBr 3 . A comparison of the Raman spectrum and the luminescence excitation sideband accompanying the 2 F 7/2 (0)→ 2 F 5/2 (2Ј) crystal-field transition reveals vibrational properties of the ͓YbBr 6 ͔ coordination unit that differ markedly from those of the CsCdBr 3 host. In particular, the vibronic transition associated with the totally symmetric ͓YbBr 6 ͔ stretching mode appears as a very weak feature at 191 cm Ϫ1 in the Raman spectrum, whereas the totally symmetric ͓CdBr 6 ͔ stretching mode of the CsCdBr 3 bulk, which appears as a strong feature at 162.5 cm Ϫ1 in the Raman spectrum, is only weakly discernible in the sideband. This is direct evidence for a large contribution from ͓YbBr 6 ͔ local modes and a small contribution from bulk modes to the vibronic intensity. The intensity of the local mode is enhanced by approximately a factor of 2 in the Raman spectrum when the laser is tuned into resonance with the 2 F 7/2 (0)→ 2 F 5/2 (2Ј) absorption of Yb 3ϩ , providing direct confirmation of its assignment. The observation of the first and second members of a Franck-Condon progression for both the local and the bulk totally symmetric modes indicates that a ⌬ process, rather than an M process, induces the vibronic intensity. Huang-Rhys factors of S local ϭ0.010Ϯ0.002 and S bulk ϭ0.15Ϯ0.03 were determined from the data, and reflect quite different electron-phonon coupling strengths. These results suggest that multiphonon relaxation of excited electronic states proceeds by the excitation of local modes of ͓YbBr 6 ͔ followed by energy transfer to bulk modes of the lattice, possibly through a nonlinear coupling mechanism which is discussed briefly.