.[.In the present invention, methods and apparatus for making efficient
cladding pumping fiber lasers is disclosed. In particular, new fiber
cladding geometry and new method of coupling pumping laser into an
optical fiber are disclosed. Both aspects of the present invention will
facilitate the realization of high-efficiency and high-power fiber
lasers. In the present invention, cladding boundary geometry structures
that can prevent the formation of local modes are disclosed. Besides the
cladding geometry, methods for efficient coupling of diode lasers into a
laser fiber for high power injection are also disclosed. Essentially, the
new methods make it possible to transmit diode laser beams for a long
distance with substantially the same brightness. In other words, with the
methods and apparatus disclosed, a laser beam from a laser diode array
with collimating structures can be transmitted for a long distance while
the beam spot dimension including beam divergence can be kept
substantially unchanged even if the beam from said array is not
substantially collimated. With the method taught in the present
invention, laser diode array modules can be formed with laser diode
arrays (LDA) with collimating structures and relay systems. Because of
the brightness conservation nature of the modules, when a plurality of
such modules (such as 3, 9 or more than 200 pieces) are combined, the
beams from the arrays can be efficiently coupled into an optical fiber.
Thus the pumping laser coupling method can be used for the construction
of high-efficiency and high-power fiber lasers. Thus, the fiber lasers of
this invention may comprise of a fiber laser core doped with active
species, a symmetry-broken inner cladding or a multiple-imaging inner
cladding surrounding said core, a plurality of brightness
substantially-conserved laser diode array module for coupling the beam
from said laser diode array module into said inner cladding..]. .Iadd.An
apparatus for a high efficiency cladding pumping fiber laser component
includes a laser fiber having a core doped with active species disposed
along an axis. A symmetry-broken inner cladding surrounds said core for
transmitting optical energy from the inner cladding to said core. The
symmetry-broken inner cladding has a substantially rectilinear
cross-section with respect to the axis with at least two pair opposing
sides. At least one side of each pair of each opposing sides is disposed
in nonparallel relationship to its respective opposed side whereby the
inner cladding has a symmetry-broken cross-section shape that minimizes
local modes in the inner cladding. .Iaddend.