Patent ID: 8873134

Claim:
An optical amplifier, comprising: an active taper, comprising a variable mode core doped with an active rare earth dopant and extending along a taper axis, an inner cladding situated about the variable mode core, and an outer cladding situated about the inner cladding, wherein the inner cladding has an average refractive index lower than an effective refractive index of the variable mode core and the outer cladding has a refractive index lower than the refractive index of the inner cladding, wherein the variable mode core includes an input section in which the variable mode core is a few mode or a single mode core and an output section in which the variable mode core is a multimode core; a pump radiation source situated so as to direct pump radiation to at least the inner cladding; and a solid state amplifier situated to receive an amplified beam produced by optical gain in the variable mode core of the active taper and configured to amplify the received amplified beam.