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.