摘要 |
<p>The invention relates to a beam combiner for a Raman pump unit. The beam combiner is configured to receive and propagate at least two orthogonally polarised collimated light beams. The beam combiner comprises a birefringent prism and an optically isotropic prism. Each of the prisms is located in the path of the beams and configured so that the beams are substantially parallel to each other when they emanate from the beam combiner.</p> |