Title

Rare-earth doped high-power fiber lasers and amplifiers

Date of Completion

January 2001

Keywords

Engineering, Electronics and Electrical|Physics, Optics

Degree

Ph.D.

Abstract

Rare-earth doped high power fibers lasers and amplifiers are important for applications in telecommunications, laser ranging, materials processing, imaging, and medical systems. The commonly used rare-earth dopants are Er, Nd, and Yb. Both theoretical and experimental investigations of rare-earth doped high power fiber lasers and amplifiers have been conducted in this work. ^ In the first part of my thesis research, high power Er/Yb co-doped double-clad fiber lasers and amplifiers have been investigated. Double-clad fibers offer a clever solution to increasing the pump power by confining the pump light in the first cladding instead of the core. Important parameters of the double-clad fiber, such as numerical apertures, the ratio of first clad to core diameter, and doping level have been optimized by modeling the effective absorption coefficient. The theoretical and experimental results of the Er-Yb co-doped double-clad fiber lasers and amplifiers were obtained. Both Fabry-Perot (F-P) and ring fiber laser setup have been experimentally tested. Output power of 1100 mW with 3500 mW pump power has been obtained by using fiber Bragg grating with F-P cavity at 1551 nm. Several other experiments, such as CATV distribution experiment, high power super fluorescent source generation, and supercontinuum source generation have been carried out as applications for the high power fiber lasers and amplifiers. ^ A tunable single frequency high power fiber laser operating near 944 nm is important for detection of water vapor concentration in the atmosphere. In the second part of my thesis research, the co-dopant effects of Nd and Yb doped materials, which were targeted for this purpose, were investigated. The emission cross-sections and the wavelength dependences of co-dopants have been studied. The ion-pair quenching effect was also investigated. Among the silica-based materials Nd doped silica fiber glass has the largest cross section for 944 nm laser emission. The co-dopants have smaller effects on Yb than Nd. ^