Non-resonance redistribution of electron excitation energy in LiNbO3:Yb3+

Li Li, Zhang Xin-Lu, Cui Jin-Hui +2 more

Intrinsic optical bistability （IOB） in Tm3+/Yb3+ codoped laser crystal under 650 nm laser excitation is theoretically studied. Based on the theory of nonlinear coupled rate equations, we numerically analyze IOB evolutions of the populations at Tm3+/Yb3+ energy levels, and the influence of system parameters on IOB and the dynamic operation of bistable hysteresis loop. The simulation result shows the fluorescence IOB in visible-infrared spectra of Tm3+/Yb3+ codoped laser crystal under photon avalanche pumping scheme. It is found that IOB phenomena can be largely enhanced by optimizing the Tm3+/Yb3+ concentration ratio, choosing low phonon-energy crystal host and using crystal cooling technology, and also by tuning the pump laser to match the resonant frequency of Tm3+ excited-state absorption transition. Through tuning the pump laser wavelength and adjusting the rate of change in pump intensity, the controllable IOB switching can be achieved.

J.K Krebs, Uwe Happek

I. Ya. Fugol’, A. M. Ratner, Е. Ю. Тарасова

Abstract It is shown that in the process of the exciton two‐center self‐trapping the resonance bonds generating a free exciton state are redistributed so that the total resonance contribution to the energy increases. 50% of the electronic excitation is concentrated inside a two‐center quasimolecule close to the self‐trapping threshold. The rest is distributed in neighbouring atoms, resulting in a generation of weaker extrinsic bonds along with the intermolecular resonance one. The attendant deformation of the molecular term produces a decrease in the self‐trapping barrier and an appreciable increase in its transparency.

B. P. Kirsanov, E. I. Datskevich

USM ADMIN

Effects of the electron-phonon interaction for rare earth ions (RE) in crystals are multi-phonon relaxation, vibronic bands, band broadening depending on temperature or non-resonant energy transfer assisted by phonons. Since the Stark splitting for RE ions are of the order of lattice phonon energy, it could arise and other related effects, especially in the approximation of quasi-resonant processes. If the distance between two Stark levels is close to the region of resonance phonon spectrum, then electron-phonon interaction creates mixed vibronic states, which causes changes in the optical spectral lines (widening, asymmetry, splitting or displacement). The modeling of interaction of the electron-phonon resonance for RE ion Yb3+ in three different laser crystals is the purpose of this paper. Keywords: electron-phonon interaction, rare earth ions, adaptive application.

Michael J. Riley, Sonja Luethi, A. Rayner +2 more