Nonlinear upconversion-rate in Er-doped fibers

• Energy transfer between excited rare-earth ions has been widely used for realizing upconversion lasers and also recognized as a gain limiting factor in high-concentration Er-doped amplifiers. The energy transfer leads to upconversion of the excitation which for randomly distributed (not clustered) ions is called homogeneous upconversion. It was commonly assumed that the rate of homogeneous upconversion is a linear function of the population inversion N-2. However, recently published Monte Carlo simulations predict that the homogeneous upconversion rate is a nonlinear function of N-2 and that it, moreover, depends on the pump and signals rates. In this paper we review some of our experimental results confirming those predictions. We also propose a statistical, analytical model describing the observed homogeneous upconversion behavior in Er-doped fibers.

Nyckelord

up-conversion

980 nm

silica

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