Survey of second harmonic generation in commercial germanium-doped fibers

Seeded optical poling is a promising and simple method to write an effective quadratic coefficient in silica optical fibers doped with germanium. We considered commercial solid core fibers since these fibers could allow for a wide adoption of optical poling. For each fiber, we optimized the poling process and analyzed the second harmonic conversion efficiencies in relation with the fiber chemical composition as obtained resorting to energy-dispersive X-ray spectroscopy. Our comprehensive investigation shows that segments of fibers spanning 20 cm, featuring a germanium content of around 6%, can effectively convert 30 mW of 1064 nm light with efficiencies hovering around 1%.