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Excited State Characteristics of Optoelectronic Materials Based 13 on RE3+ Ions
Czeslaw Koepke, Dawid Piatkowski, Patrycjusz Stremplewski, Marek Rozanski and Krzysztof Wisniewski

Excited state characteristics (ESC) defined as the spectra being composition of three components: the excited state absorption (ESA), stimulated emission (SE), and ground state absorption bleaching (GSB) are presented and discussed for several matrices activated by RE ions. A special stress is put upon that information which can be derived from such characteristics. For example tens of new channels of excitation leading to various anti-Stokes emissions based on e.g. the ESA-induced upconversion, energy transfer-induced upconversion (ETU) or photon avalanche (PA) have been predicted. Some of them have already been verified experimentally, others are waiting for verification. Our technique allows to register the ESA/gain spectra originating from different states, whenever the states differ distinctly in their lifetime. The method of analysis of the excited state characteristics is also used to evaluation of prototype optic fibers activated by Nd3+ and Er3+ ions. New interesting effects appear when performing measurements of the excited state characteristics of a long fiber amplifier. We try to interpret some of them.

Keywords: Excited state absorption, optical gain, rare-earth-doped materials, upconversion, upconverted emission.

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