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We demonstrate a multi core multi dopant fiber which, when pumped with a single pump source around ∼800 nm, emits a more than one octave-spanning fluorescence spectrum ranging from 925 to 2300 nm. The fiber preform is manufactured from granulated oxides and the individual cores are doped with five different rare earths.
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In this paper, we propose, through different examples, some alternate designs and methods of manufacturing for pushing the limits of active fiber optics. The novelty comes from modal filtering under laser operation, fabrication of fibers using silica powders and laser with extended spectrum of emission.
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We demonstrate 74% slope efficiency CW laser emission from a non CVD Yb3+-doped fiber. This multimode fiber exhibiting a 314 mm2 Yb3+-doped core area constitute a first step toward singlemode fiber for high power delivery..
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We demonstrate a single-core multiply doped fiber that, when pumped with a single pump source of ~800 nm, emits a more than two-octaves-spanning fluorescence spectrum ranging from 365 to 2300 nm. The fiber preform is manufactured from granulated oxides, and the core is doped with five different rare earths. At a pump power of 250 mW the total emitted power is 34 чW; given a core diameter of 6.5 чm and a numerical aperture of 0.1. We also demonstrate direct diode pumping of the fiber.
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A fibre is manufactured with a 6.5 чm core doped with five different rare earths: Nd3+, Ho3+, Er3+, Tm3+, and Yb3+. Co-doping with 7 at. % Al3+ leads to an index step чn of 3.44·10-3 at 804 nm corresponding to a numerical aperture NA of 0.1. Upon excitation with light of 804 nm wavelength, fluorescence of the five dopant ions occurs. Excited state absorption and / or energy transfer up-conversion lead to an extremely broad spectrum ranging from 365 nm up to 2300 nm. With single-beam spectrophotometers the emitted power is measured. With an output power of 34 чW a radiance exceeding 3 kW·sr-1·cm-2 is reached. The broad spectrum leads to a very short coherence length of 250 nm FWHM.
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