High power operation of cladding pumped holmium-doped silica fibre lasers

Abstract

We report the highest power operation of a resonantly cladding-pumped, holmium-doped silica fibre laser. The cladding pumped all-glass fibre utilises a fluorine doped glass layer to provide low loss cladding guidance of the 1.95 µm pump radiation. The operation of both single mode and large-mode area fibre lasers was demonstrated, with up to 140 W of output power achieved. A slope efficiency of 59% versus launched pump power was demonstrated. The free running emission was measured to be 2.12-2.15 µm demonstrating the potential of this architecture to address the long wavelength operation of silica based fibre lasers with high efficiency.

Holmium doped fibre optimised for resonant cladding pumping

“…The corresponding slope efficiency with respect to absorbed pump power was 67%, which, to the best of our knowledge, represents the highest reported efficiency for a cladding pumped Holmium doped fibre laser [2,3,6].…”

“…Recently, operational efficiencies for resonantly pumped Ho:silica fibre close to the quantum limit have been demonstrated for core pumped lasers [1]. To further power scale Ho:fibre lasers, development of cladding-pumped fibre configuration is necessary and indeed has enabled scaling of such fibres to >400 W cw average power [2]. Conventional polymer-coated double-clad fibres have high inner-cladding propagation loss at the ~1.95 µm pump wavelength, resulting from the presence of OH -contamination and absorption in the polymer outer-cladding [3].…”

Sub-Microsecond Pulsed Pumping as a Means of Suppressing Amplified Spontaneous Emission in Tandem Pumped Fiber Amplifiers

“…Other examples of three-level lasers where tandem pumping has been applied is the use of Thulium fiber lasers to pump Holmium lasers in the 2 µm wavelength range [25]]. The only experimental examples of pulsed resonant pumping we are aware of involve pulsed pumping of Holmium [26,27] or Thulium [28][29][30] gain-switched fiber lasers (1940 nm) in order to regulate the usually chaotic pulse generation, and the average powers have been at the <8 W level.…”

Highly efficient mid-infrared 2 μm emission in Ho^3+/Yb^3+-codoped germanate glass

“…Ho 3+ 2.0 μm emission has already been investigated in different kind of glasses and 2.0 μm laser output has been obtained as well [6][7][8][9]. Output power of 140 W at 2.1 μm was demonstrated by using a Ho 3+ -doped silica glass fiber laser in 2013 [10]. A maximum slope efficiency of 78% and output power of 516mW at 2.08 μm has been obtained in a Ho 3+ -doped fluoride glass fiber in 2011 [11].…”