Laser and optical amplifier

An optical rod laser or amplifier comprising rod and a pump radiation source configured to generate pump radiation which is received through an input end of the rod, the rod comprising a doped material which is configured to guide the pump radiation, the rod being configured to generate or amplify signal radiation when the pump radiation passes through it, the signal radiation being unguided by the rod,

• wherein the rod laser or amplifier further comprises a first reflector configured to reflect pump radiation which has travelled from the input end to an output end of the rod, and further comprises a second reflector configured to selectively reflect a portion of pump radiation which has travelled from the output end to the input end of the rod, wherein a selection of the portion of pump radiation to be reflected by the second reflector depends upon one or more of:
• a spatial position of the pump radiation, a direction of the pump radiation, and a polarisation of the pump radiation.

An optical fibre comprising a doped core which is configured to generate signal radiation when pump radiation passes through the doped core and to guide the signal radiation, the optical fibre further comprising cladding which is configured to guide the pump radiation,

• wherein the optical fibre further comprises a first reflector configured to reflect pump radiation which has travelled from an input end to an output end of the optical fibre, and further comprises a second reflector configured to selectively reflect a portion of pump radiation which has travelled from the output end to the input end of the optical fibre, wherein a selection of the portion of pump radiation to be reflected by the second reflector depends upon one or more of:
• a spatial position of the pump radiation, a direction of the pump radiation, and a polarisation of the pump radiation.