Rare-earth doped fiber and fiber laser apparatus
A rare-earth doped fiber includes: a core having a radius R and having a doped region to which a rare-earth element has been doped, the doped region ranging from a center of the core to a radius R re ; and a cladding surrounding a circumference of the core and having a refractive index lower than a refractive index of the core. A normalized frequency V at an operating wavelength is greater than or equal to 2.4 and less than or equal to 4.5. The radius R re is in a range of 0<R re < ( 0.0247 V 2 - 0.3353 V + 1.6474 ) R .
1 . A rare-earth doped fiber comprising:
a core having a radius R and comprising a doped region to which a rare-earth element has been doped, the doped region ranging from a center of the core to a radius R re ; and
a cladding surrounding a circumference of the core and having a refractive index lower than a refractive index of the core,
wherein a normalized frequency V at an operating wavelength is greater than or equal to 2.4 and less than or equal to 4.5, and
the radius R re is in a range of 0<R re <(0.0247V 2 −0.3353V+1.6474) R.
2 . The rare-earth doped fiber as recited in claim 1 , wherein the radius R re is in a range of 0.1R<R re <(0.0247V 2 −0.3353V+1.6474) R.
3 . The rare-earth doped fiber as recited in claim 2 , wherein the radius R re is in a range of 0.3R<R re <(0.0247V 2 −0.3353V+1.6474) R.
4 . The rare-earth doped fiber as recited in claim 1 , wherein the normalized frequency V is greater than or equal to 2.4 and less than or equal to 4.2.
5 . The rare-earth doped fiber as recited in claim 4 , wherein the normalized frequency V is greater than or equal to 2.4 and less than or equal to 3.9.
6 . The rare-earth doped fiber as recited in claim 1 , wherein the radius R of the core is less than or equal to V/0.34 μm.
7 . The rare-earth doped fiber as recited in claim 1 , wherein the rare-earth element is ytterbium.
8 . A fiber laser apparatus comprising:
the rare-earth doped fiber as recited in claim 1 ; and
at least one pumping light source operable to generate a pumping light for exciting the rare-earth element doped to the rare-earth doped fiber and provide the pumping light to the rare-earth doped fiber.
9 . The fiber laser apparatus as recited in claim 8 , wherein at least a portion of the rare-earth doped fiber is bent with a bend radius of 200 mm or less.
10 . The fiber laser apparatus as recited in claim 9 , wherein at least a portion of the rare-earth doped fiber is bent with a bend radius of 100 mm or less.