Patent ID: 8315289
Filing Date: 2012-11-20
Classification: H01S

Abstract:
1. An optical apparatus comprising: first and second gain media each of which exhibits polarisation dependent absorption along two axes, each gain medium having a weakly absorbing axis and a strongly absorbing axis; and an optical pump source arranged to direct non-plane polarised pump light towards the first gain medium such that the non-plane polarised pump light entering this gain medium has a component of its polarisation parallel to the weakly absorbing axis of the first gain medium; wherein the second gain medium is arranged such that a significant proportion of the component of light exiting the first gain medium with polarisation parallel to the weakly absorbing axis of the first gain medium is incident upon the second gain medium with polarisation which is substantially parallel to the strongly absorbing axis of the second gain medium; wherein the optical apparatus is configured such that light emitted by the first gain medium has the same polarisation within the second gain medium as light emitted by the second gain medium; wherein the second gain medium is oriented such that the strongly absorbing axis of the second gain medium is substantially parallel to the strongly absorbing axis of the first gain medium.