Double-Clad Bismuth-Doped Fiber with a Rectangular Inner Cladding for Laser Application
Alexander Vakhrushev,
Andrey Umnikov,
Sergey Alyshev,
Aleksandr Khegai,
Elena Firstova,
Lyudmila Iskhakova,
Aleksei Guryanov,
Mikhail Melkumov,
Sergei Firstov
Affiliations
Alexander Vakhrushev
Prokhorov General Physics Institute of the Russian Academy of Sciences (GPI RAS), Dianov Fiber Optics Research Center, 38 Vavilov Str., 119333 Moscow, Russia
Andrey Umnikov
G.G. Devyatykh Institute of Chemistry of High-Purity Substances of the Russian Academy of Sciences, 49 Tropinin Str., 603951 Nizhny Novgorod, Russia
Sergey Alyshev
Prokhorov General Physics Institute of the Russian Academy of Sciences (GPI RAS), Dianov Fiber Optics Research Center, 38 Vavilov Str., 119333 Moscow, Russia
Aleksandr Khegai
Prokhorov General Physics Institute of the Russian Academy of Sciences (GPI RAS), Dianov Fiber Optics Research Center, 38 Vavilov Str., 119333 Moscow, Russia
Elena Firstova
Prokhorov General Physics Institute of the Russian Academy of Sciences (GPI RAS), Dianov Fiber Optics Research Center, 38 Vavilov Str., 119333 Moscow, Russia
Lyudmila Iskhakova
Prokhorov General Physics Institute of the Russian Academy of Sciences (GPI RAS), Dianov Fiber Optics Research Center, 38 Vavilov Str., 119333 Moscow, Russia
Aleksei Guryanov
G.G. Devyatykh Institute of Chemistry of High-Purity Substances of the Russian Academy of Sciences, 49 Tropinin Str., 603951 Nizhny Novgorod, Russia
Mikhail Melkumov
Prokhorov General Physics Institute of the Russian Academy of Sciences (GPI RAS), Dianov Fiber Optics Research Center, 38 Vavilov Str., 119333 Moscow, Russia
Sergei Firstov
Prokhorov General Physics Institute of the Russian Academy of Sciences (GPI RAS), Dianov Fiber Optics Research Center, 38 Vavilov Str., 119333 Moscow, Russia
In this paper, we report the latest research results on the fabrication of double-clad Bi-doped germanosilicate core fibers with a rectangular inner cladding design for improved laser performance in the near-IR spectral region. Detailed comparative analysis of the absorption characteristics of the Bi-doped fibers with a circular- and rectangular-shaped inner cladding was performed. A series of cladding-pumped, Bi-doped fiber lasers emitting near 1.46 µm was developed using the semiconductor’s multi-mode fiber-coupled laser diodes at λ = 808 nm. The peculiarities of the laser parameters of the fabricated active fibers with the double-clad design were thoroughly studied by analyzing the dependencies of the slope efficiency of the lasers, namely the pump power, active fiber length and core-to-inner-cladding area ratio. The obtained results show that the rectangular design provided enhanced cladding absorption and improvements in laser performance. In particular, we achieved maximal slope efficiencies of 5.5% and 4.3% for the absorbed pump power introduced into the inner cladding with cross-section areas of 80 × 80 µm2 and 125 × 125 µm2, respectively. Multi-wavelength lasing operation in a free-running cavity due to a few modes’ propagation regimes was found using the Bi-doped fiber with an 80 × 80 µm2 inner cladding.
