E- and S-band bismuth-doped fiber amplifier

High-power lasers operating at the E- and S-bands that overlaps with the strong absorption band of water molecules have been exploited for applications such as medical diagnoses, laser therapy and lipolysis. This type of lasers can be realized with a MOPA (master oscillator power amplifier) configuration, consisting of a seed laser and a fiber amplifier, which allows one to achieve easily boosting the output power. However, the efficient fiber amplifiers operating in the E- and Sbands using most rare-earth-doped silica fibers is inaccessible. In contrary, the optical fibers doped with bismuth (Bi) capable of providing broadband amplification from 1100 to 1800 nm can be utilized to build a desired fiber amplifier. In this work, we demonstrated the output characteristics of developed amplifiers based on a Bi-doped 5GeO2 − 95SiO2 fiber (BGSF) drawn from a preform fabricated by the modified chemical vapour deposition (MCVD) technique. The corepumped fiber amplifiers are characterized by a small-signal gain of >20 dB at a wavelength of ~1440 to 1450 nm and the noise figure of ~4.5 to 6 dB. In addition, the fiber amplifier was employed to amplify a signal from a tunable continuous wave laser from 1390 to 1510 nm. This work presents the significance of Bi-doped fibers to build a fiber amplifier across E- and S-bands which could be attractive for medical diagnoses and laser therapy applications.