ULTRA HIGH POWER SINGLE MODE FIBER LASER SYSTEM

摘要

Ultra-high power fiber laser systems comprise an integrated fiber optic booster consisting of a straight, short optical fiber rod and an optical fiber having a core commonly composed of 0.1 or more numerical apertures and doped with ions of one or more rare earth elements across the entire cross section. The optical fiber rod portion is of short length not exceeding about tens of centimeters and has a generally conical cross section extending from a generally uniformly formed optical fiber portion. The core extending along the fiber portion can support an SM or a very small number of HOMs that are guided along the core in the direction of propagation and coupled to the small diameter end of the conical core of the fiber rod. The opposite large diameter end of the conical core supports multimodes in a basic mode that overlaps a core cross-sectional area of at least 0.65 ² along the entire length of the core. The disclosed output system further includes a pump source having a NA equal to at most the NA of the core and emitting a high power multimode pump light coupled to the large diameter end of the core in the opposite propagation direction. The pump is configured to emit pump light at such a density that the non-overlapping area around the core is bleached while the amplification of the fundamental mode continues to the overlapped area of the core. As a result, the disclosed system has an average power of several kW in the CW region or a peak power of one or more MW in the pulse region of the system operation and emits the signal light in substantially basic mode.