Optical amplifier

An optical amplifier comprising:

• first optics configured to receive a laser beam and output an expanding beam;
• a gain medium comprising material configured to provide optical gain to laser light transmitted therethrough, said gain medium having an input surface and an output surface separated from each other in a longitudinal direction by a length, said input surface extending in first and second directions orthogonal to said longitudinal direction so as to have an input area, said output surface extending in said first and second directions orthogonal to said longitudinal direction so as to have an output area, said output area being larger in both said first and second directions than said input area, said gain medium being positioned such that said expanding beam is received into said input surface and output through said output surface, said expanding beam having a larger beam size in both said first and second directions at said output surface than at said input surface;
• an optical pump source configured to provide output pump radiation to said gain medium such that said material provides optical gain to said expanding beam transmitted therethrough, and
• second optics positioned to receive the laser beam output from the gain medium and to reduce the divergence of said laser beam.