All-Fiber Laser System With Intrinsic Isolation Of Backward-Propagating Optical Radiation

An all-fiber laser system for processing highly reflective materials, comprising:

• a seed laser configured to generate a signal laser beam at a processing wavelength;
• at least one pump light source configured to provide a pump light at a pump wavelength;
• one or more isolating side-pumped signal-and-pump combiners, each comprising:
• a signal fiber configured to transmit the signal laser beam;
• one or more pump fibers configured to deliver the pump light;
• and
• a coupling region in which the pump light is side-coupled into the signal fiber while the signal laser beam propagates without interruption;
• a gain fiber optically coupled to the signal fiber of each of the one or more isolating side-pumped signal-and-pump combiners, the gain fiber being doped with rare-earth ions and configured to amplify the signal laser beam using the pump light;
• a cladding power stripper disposed downstream of the gain fiber and configured to dissipate a cladding-guided optical radiation propagating in at least one of a forward direction or a backward direction along both the gain fiber and the signal fiber of each of the one or more isolating side-pumped signal-and-pump combiners, while allowing a core-guided signal radiation to propagate substantially unaffected;
• and
• an output fiber optically coupled to the gain fiber and configured to deliver an amplified output laser beam to a reflective workpiece, wherein:
• the one or more isolating side-pumped signal-and-pump combiners are configured to provide intrinsic isolation that inhibits a backward-propagating signal light and a backward stimulated Raman scattering (SRS) light from coupling into the one or more pump fibers of each of the one or more isolating side-pumped signal-and-pump combiners, thereby reducing propagation of a back-reflected optical radiation from highly reflective materials toward the at least one pump light source;
• the all-fiber laser system operates without free-space optical components between the seed laser and the output fiber, thereby enhancing resistance to any optical damage caused by a back reflection;
• and
• the cladding power stripper is non-wavelength-selective and removes the optical radiation based on spatial mode confinement rather than wavelength.