Fiber amplifier having an anisotropic numerical aperture for efficient coupling of pump energy

A fiber amplifier comprising:

• a longitudinally extending inner core;
• an outer core surrounding said inner core and extending longitudinally therealong;
• and
• a cladding layer at least partially surrounding said outer core, wherein said outer core and said cladding layer are structured such that a numerical aperture of the fiber amplifier in a first direction is different than the numerical aperture of the fiber amplifier in a second direction.

A fiber amplifier comprising:

• a longitudinally extending inner core;
• an outer core surrounding said inner core and extending longitudinally therealong, wherein said outer core includes major opposed surfaces and minor opposed surfaces;
• and
• a cladding layer at least partially surrounding said outer core, wherein at least a portion of said cladding layer interfaces with the major opposed surfaces of said outer core to thereby define a first numerical aperture, and wherein the minor opposed surfaces of said outer core at least partially interface with a material to thereby define a second numerical aperture that is different from the first numerical aperture.

A fiber amplifier comprising:

• a longitudinally extending inner core;
• an outer core surrounding said inner core and extending longitudinally therealong, wherein said outer core includes a material disposed therein;
• and
• a cladding layer at least partially surrounding said outer core, wherein at least a portion of said cladding layer interfaces with the said outer core to thereby define a first numerical aperture, and wherein said outer core interfaces with the material to thereby define a second numerical aperture that is different from the first.