Cladding-pumped 3-level fiber laser/amplifier

A fiber laser comprising:

• a broad-area laser diode having a pump light having an output power of at least 1 Watt;
• a double-clad optically active fiber having a first end for receiving the pump light and a second end for outputting a laser signal, the double-clad optically active fiber including
• a core for supporting close to a single-mode transmission of the laser signal, the core having a cross-sectional core area, the core doped with a plurality of optically excitable dopants having a transition requiring a high level of inversion at a desired signal wavelength of the laser signal;
• an inner cladding disposed adjacent to the core having an aspect ratio greater than 1.5 and configured sufficiently small to match a laser mode field geometry of the pump light to allow the inner cladding to optically deliver the pump light to the core at a high pump power density, the inner cladding having a cross-sectional area approximately 2 to 25 times larger than the core area to allow a sufficiently high overlap between dopants in the core and the pump light, such that the high pump power density and the high overlap between dopants and the pump light provide the required level of inversion for lasing with a low power threshold and high efficiency;
• and
• an outer cladding disposed adjacent to the inner cladding having an index of refraction less than the inner cladding for confining the pump light.

A fiber amplifier comprising:

• a broad-area laser diode having a pump light having an output power of at least 1 Watt;
• a double-clad optically active fiber including
• a core for supporting close to a single-mode transmission of the amplified signal, the core having a cross-sectional core area, the core doped with a plurality of optically excitable dopants having a transition requiring a high level of inversion at a desired signal wavelength of the amplified signal;
• an inner cladding disposed adjacent to the core having an aspect ratio greater than 1.5 and configured sufficiently small to match a laser mode field geometry of the pump light to allow the inner cladding to optically deliver the pump light to the core at a high pump power density, the inner cladding having a cross-sectional area approximately 2 to 25 times larger than the core area to allow a sufficiently high overlap between dopants in the core and the pump light, such that the high pump power density and the high overlap between dopants and the pump light provide the required level of inversion for amplification with a low power threshold and high efficiency;
• and
• an outer cladding disposed adjacent to the inner cladding having an index of refraction less than the inner cladding for confining the pump light.