Cross-relaxation deactivation of the ground state of ions of rare-earth elements in crystals

An unconventional system for the excitation of crystals activated with Tm3+ and Er3+ ions was proposed and implemented experimentally. This eliminated the need for any direct interaction between the external electromagnetic field and ions in the ground energy state. It was shown that efficient filling of unstable states of these ions may be achieved as a result of the absorption of photons due to a transition from an excited state and subsequent cross relaxation of the excitation.