Процессы передачи энергии в эвлитите Sr-=SUB=-3-=/SUB=-Y(PO-=SUB=-4-=/SUB=-)-=SUB=-3-=/SUB=-, по отдельности и одновременно легированном ионами Tb-=SUP=-3+-=/SUP=- и Tm-=SUP=-3+-=/SUP=-

In this work the optical spectroscopy and the energy transfer processes involving the Tb3+and Tm3+ ions, have been studied in eulytite double phosphate hosts of the type Sr3Y(PO4)3 doped with various amounts of the two Ln ions. It has been found that several energy transfer and cross-relaxation processes are active in this class of materials, upon excitation in the 5D4 level of Tb, and in the 1G4 one of Tm. In particular, a Tb→Tm transfer of excitation has been found to quench strongly the 5D4 level of Tb. This process occurs with a transfer efficiency increasing from 0.08 to 0.62, for a donor concentration of 2 mol%, and an acceptor concentration increasing from 2 to 15 mol%. The emission spectra are strongly affected by the presence of Tb⟷Tm energy transfer, and Tm→Tm cross relaxation processes.

MANIFESTATION IN IR-LUMINESCENCE OF THE CROSS RELAXATION PROCESSES BETWEEN NV CENTERS IN WEAK MAGNETIC FIELDS

We present a combined experimental and theoretical study of the effect of magnetic field on the luminescence from an ensemble of NV centers in diamond. It was found that the intensity of infrared luminescence associated with transitions between singlet levels of NV centers shows a pronounced increase of a near-zero magnetic field. The influence of the power and polarization of laser radiation on the amplitude and shape of the revealed local maximum in IR-luminescence of NV centers is investigated. An eight-level photophysical model of an NV center in the presence of an arbitrarily directed magnetic field has been constructed and on its basis the calculation has been performed of the luminescence intensity emitted by an ensemble of NV center, both in the visible and infrared regions of the spectrum. It is shown that the phenomenological allowance for the cross-relaxation of NV centers between each other and with other paramagnetic centers in a diamond within the framework of this model allows describing the experimentally observed fluorescence features of an ensemble of NV centers in the presence of weak magnetic fields.

Energy Transfer and Cross-Relaxation Induced Efficient 2.78 μm Emission in Er3+/Tm3+: PbF2 mid-Infrared Laser Crystal

An efficient enhancement of 2.78 μm emission from the transition of Er3+: 4I11/2 → 4I13/2 by Tm3+ introduction in the Er/Tm: PbF2 crystal was grown by the Bridgman technique for the first time. The spectroscopic properties, energy transfer mechanism, and first-principles calculations of as-grown crystals were investigated in detail. The co-doped Tm3+ ion can offer an appropriate sensitization and deactivation effect for Er3+ ion at the same time in PbF2 crystal under the pump of conventional 800 nm laser diodes (LDs). With the introduction of Tm3+ ion into the Er3+: PbF2 crystal, the Er/Tm: PbF2 crystal exhibited an enhancing 2.78 μm mid-infrared (MIR) emission. Furthermore, the cyclic energy transfer mechanism that contains several energy transfer processes and cross-relaxation processes was proposed, which would well achieve the population inversion between the Er3+: 4I11/2 and Er3+: 4I13/2 levels. First-principles calculations were performed to find that good performance originates from the uniform distribution of Er3+ and Tm3+ ions in PbF2 crystal. This work will provide an avenue to design MIR laser materials with good performance.