Cladding-pumped Raman fiber amplifiers (RFA) have been proposed as gain media to achieve power scaling. It is well-known that the onset of the modal instability (MI) phenomenon is a limiting factor for achieving higher output powers in Yb-doped fiber amplifiers with good beam quality. In this paper, we present an analytical approach to the investigation of the MI phenomenon in high-power, cladding-pumped RFAs. By utilizing the conservation of the number of photons and the conservation of energy in the absence of loss, the nonlinear equations for the propagation of the pump power and the total signal power can be decoupled from one another. Decoupling lead to exact solutions for the pump power and transverse modes signal powers. Further we investigate various MI suppression techniques including increasing the seed power and gain-tailored design.

Date Published: 4 March 2015
PDF: 9 pages
Proc. SPIE 9344, Fiber Lasers XII: Technology, Systems, and Applications, 93442X (4 March 2015); doi: 10.1117/12.2083038

Published in SPIE Proceedings Vol. 9344:
Fiber Lasers XII: Technology, Systems, and Applications
L. Brandon Shaw, Editor(s)