Ultra high power single mode fiber laser system

摘要

An ultra-high power fiber laser system includes a single-piece fiber booster configured with fiber and straight short rod fiber portions which have in common a core configured with a numerical aperture≧0.1. The rod fiber portion has a length≦a few tens of centimeters and has a frustoconical cross-section expanding from the uniformly configured fiber portion. The core extending along the fiber portion supports a single mode (SM) or very low number of HOMs, whereas the large-diameter end of the frustoconical core portion supports a fundamental mode and high order multiple modes. The disclosed booster is energized by a pump source configured to emit pump light with such a density that while amplification of the fundamental mode continues in the central area of the core, a peripheral non-overlapped area of the core is bleached. The disclosed booster emits signal light in substantially a fundamental mode.

主权项

1. An ultra-high power single mode (“SM”) fiber laser system comprising:
a monolithic fiber to fiber-rod optical amplifier including elongated input fiber and output fiber rod portions, the amplifier being structured with a core and a cladding surrounding the core between opposite ends of the amplifier, the core including: a flexible, uniformly dimensioned input core region extending along a length of the input fiber portion and configured to waveguide a SM in a propagating direction, and an output core region extending from the input core region along a length of the fiber rod portion towards an output end of the core, which is capable of supporting fundamental and high order modes with a mode area of the fundamental mode (“FM”) overlapping a central zone of a cross-section area of the core, the fiber rod portion being configured with a length between about 10 cm and about 30 cm, and a numerical aperture of at least about 0.1; and an ultra-bright multimode pump source operative to emit pump light having a numerical aperture at most equal to that of the output end of the core and coupled into the output core end in a counter-propagating direction, a power density of the pump light being much higher than a density required to bleach a zone of the core not overlapped by the FM, wherein the amplifier emits an output in the SM with an average output power exceeding about 5 kW or a peak power reaching a GW level.