ABSTRACT
In this paper, we focus on the fabrication and investigation of optical properties of W-type and Graded-index single-mode Bi-doped germanosilicate fibers. The laser and gain characteristics of Bi-doped fibers of new designs were studied. It was shown that by variation of doping profile, it is possible to change characteristic parameters (active absorption, unsaturable loss level) of the active medium and, as a consequence, achieve an improvement of the performance of the optical devices based on these types of fibers. As a progress one can consider the creation of a Bi-doped fiber laser operating at 1460 nm with a record efficiency of 72% using a relatively short active fiber (L = 75 m); and a 20-dB Bi-doped fiber amplifier (L = 120 m) with a pump power of 45 mW (for the input signal powers lower than 30 µW) having a high gain efficiency of 0.52 dB/mW. We suggest that the obtained results could be a driver for further investigation in this direction.
ABSTRACT
A watt-level all-fiber laser radiating at the wavelength of 1.7 µm in a continuous-wave regime was developed by using bismuth-doped high-germania optical fiber. A maximum slope efficiency of 33% with respect to the launched pump power was achieved. The dependencies of the slope efficiencies of bismuth-doped fiber laser versus the length of active fiber and reflectivity of the output mirror were obtained.
ABSTRACT
Excited-state absorption (ESA) in various bismuth-doped fibers (BDFs) was investigated. No significant ESA in IR emission bands of Bi-doped germanosilicate and phosphosilicate fibers was found. Considerable ESA was observed in Bi-doped aluminosilicate fibers at 800-1700 nm. The ESA spectra of the aluminosilicate BDFs with different bismuth concentration were measured at room and 77 K temperature. Significant dependence of the ESA on the bismuth concentration and the fiber temperature was found.
