Patent ID: 8837870

Claim:
A fiber laser device, comprising: a laser source configured to emit a source laser beam, wherein the source laser beam is divergent; a coupling optical system configured to focus the source laser beam to form a convergent laser beam; a birefringent beam separator configured to receive the convergent laser beam and to split the convergent laser beam into an o ray and an e ray which have mutually orthogonal polarizations; and a polarization maintaining fiber comprising a fiber core characterized by a core diameter, wherein after the o ray and the e ray exit birefringent beam separator, the o ray and the e ray are separated by a distance that is larger than the fiber core of the polarization maintaining fiber, wherein the polarization maintaining fiber is positioned to couple one of the o ray and the e ray into the fiber core, wherein the one of the o ray and the e ray transmits through the polarization maintaining fiber to form an output laser beam.