title: Optimization of pump absorption in MOF lasers via multi-long-period gratings: design strategies.
abstract: Different strategies for designing optical couplers, optimized to enhance the pump absorption in the rare-earth-doped core of microstructured fiber lasers, are illustrated. Three kinds/configurations of optical couplers have been designed and compared as examples of the different design strategies which can be followed. Their effectiveness to enhance the performance of an ytterbium-doped, double cladding, microstructured optical fiber laser has been accurately simulated. They consist of a suitable cascade of multiple long-period gratings (MLPGs) inscribed in the fiber core region. The characteristics of the MLPG couplers have been simulated via a homemade computer code based on both rate equations and an extended coupled mode theory. The proposed MLPG couplers seem particularly useful in the case of low rare-earth concentration but, even for a middle-high ytterbium concentration, as N(Yb)=5×10(25) ions/m(3), the slope efficiency S can be increased up to 20%, depending on the fiber length.
authors.affiliation: Dipartimento di Elettrotecnica ed Elettronica Politecnico di Bari Via E. Orabona 4-70125 Bari, Italy. prudenzano@poliba.it
authors.forename: Francesco
authors.initials: F
authors.lastname: Prudenzano
authors.forename: Luciano
authors.initials: L
authors.lastname: Mescia
authors.forename: Tommaso
authors.initials: T
authors.lastname: Palmisano
authors.forename: Michele
authors.initials: M
authors.lastname: Surico
authors.forename: Marco
authors.initials: M
authors.lastname: De Sario
authors.forename: Giancarlo Cesare
authors.initials: GC
authors.lastname: Righini