Fabrication and laser performance of triple-clad Yb-doped aluminophosphosilicate fiber

Abstract

Abstract We fabricated an Yb-doped triple-clad fiber consisting in adding to aluminophosphosilicate core and F300-pump cladding, low-refractive-index fluorine doped silica cladding, and demonstrated its laser performance based on an all-fiber oscillator. MCVD system, all-gas-phase chelate precursor doping technique, and a simple overcladding process were applied to make Yb-doped aluminophosphosilicate triple-clad fiber preform. Ultra-thin substrate tube and a two-stage deposition process were proposed to decrease and offset elements evaporation. The outer region of fiber core was tested with ∼1050 ppm Yb2O3, ∼10,800 ppm Al2O3, and ∼9950 ppm P2O5, while the central region was doped with ∼600 ppm Yb2O3, 8100 ppm Al2O3, and ∼7000 ppm P2O5, respectively (ppm is in molar here). Two-stage deposition process and triple-clad design results in pump absorption from Yb3+ ions about 0.67 dB/m at 915 nm. Tested in an all-fiber oscillator configuration forward-pumped by 915 nm laser diodes, 28 m-long triple-clad fiber presented 560 W laser output with optical-to-optical efficiency of 68.7%, and the corresponding beam quality M2 is ∼1.18. The results indicate all-gas-phase chelate precursor doping technique in combination with overcladding technique is potential to manufacture high power triple-clad fiber, and ultra-thin substrate tube as well as two-stage deposition process are very effective ways to decrease and offset element evaporation.