Investigation of modal properties of microstructured optical fibers with large depressed-index cores

Abstract

We present what is, to the best of our knowledge, the first systematic study on how negative core-cladding index difference influences microstructured optical fiber's modal behavior. Single-mode lasing has been realized for short-length cladding-pumped phosphate glass microstructured fibers with large depressed-index Er(3+)-Yb(3+)-codoped cores.

Ytterbium doped phosphate glass photonic crystal fiber laser

“…In the structure, it could be also implemented the high stress originating from the PCF fabricating process and also from the use of doped and undoped glass that slightly differ with rheological and refractive index properties. Those reasons can deteriorate the quality of the mode [17]. The laser radiation is spatially coherent what was proved in Young's experiment.…”

“…The numerical aper− ture of the mode was 0.05. There was also measured the value of 1. lications [11,17]. The reason of that behaviour is the PCF fundamental mode shape deviates from a Gausian mode due to the hexagonal lattice of PCF structures.…”

Index matching between passive and active tellurite glasses for use in microstructured fiber lasers: Erbium doped lanthanum-tellurite glass

“…This is of particular importance when doping only the core of a MOF as the refractive index of the core may be reduced to below the effective index of the holey cladding, thus preventing index guiding. The guidance can be restored by increasing the air fraction of the microstructure in the cladding [9], or by modifying the composition of the core and cladding glasses to minimize the difference in their refractive indices. The addition of La 2 O 3 to a tellurite glass promises index matching between undoped and rare earth doped glasses.…”

Spectroscopy of erbium in La³⁺-doped tellurite glass & fibres

“…When high index glasses are doped the refractive index decreases [1,2]. The loss of light confinement caused by this refractive index change in an optical fibre has previously been addressed through the modification of the cladding structure [2] and also through the use of different host glass compositions in the core and cladding regions.…”