Ultra-high power single mode fiber laser system with non-uniformly configured fiber-to-fiber rod multimode amplifier

摘要

A high power single mode (“SM”) laser system includes an amplifier configured with a monolithic fiber to rod fiber waveguide which is structured with a multimode (“MM”) core and at least one cladding surrounding the core. The MM core is configured with a small diameter uniform input region receiving and guiding a SM signal light, a mode-transforming frustoconical core region expanding outwards from the input region and a relatively large diameter uniform output portion. The high power laser system is further structured with a MM pump light delivery fiber having a numerical aperture NA2, which is at most equal to that one of the output core portion. The amplifier and pump light output fiber traverse an unconfined delivery cable and terminate upstream from a mirror which is configured to focus the incident pump light into the core of the amplifier in a counter-propagating direction. The mirror is further structured with an opening aligned with the optical axis of the amplifier and configured to provide a lossless passage of amplified signal light in a propagating direction.

主权项

1. An ultra-high power fiber laser system, comprising:
a base laser console enclosing:
a single mode (“SM”) seed source emitting SM signal,a SM passive fiber receiving and guiding the SM signal light in a propagating direction,a fiber pigtailed laser diode pump outputting pump light, anda utility assembly configured to support a laser system operation including control and safety electronics; an optical laser head spaced from the base laser console; at least one flexible delivery cable extending between the console and laser head; a fiber to fiber rod booster amplifier having a major length traversing the delivery cable and provided with an output end which is directly coupled to the laser head, the booster amplifier being configured with an all doped multimode (MM”) monolithic core configured with at least:
a uniformly dimensioned input core region coupled to a downstream end of a core of the SM passive fiber, the cores of respective input core region and SM fiber being configured with respective mode field diameters (“MFD”) which substantially match one another,a mode transforming core region expanding from the input core section and configured to expand the MFD of the SM while preventing an excitation of high order modes,an output amplifying uniformly dimensioned core region extending from the mode transforming core region and having a diameter larger than that of the input core region, wherein the booster fiber amplifier is operative to emit system output light in substantially the SM with a power varying in a kW-MW range; a mirror mounted in the laser head and spaced downstream from the booster amplifier; and a least one MM pump light delivery fiber extending through the delivery cable and guiding the pump light so that the pump light is incident on the mirror configured to redirect the pump light in a counter-propagating direction to end-pump the MM core of the booster amplifier.