Abstract: A method of optimising the focus of a fibre laser is described, which comprises positioning the output of a fibre laser relative to a workpiece; measuring at least a portion of back reflected radiation from the workpiece (step 52); determining an integral of this; changing the relative position of the output and the workpiece one or more times (step 54,56), each time determining an integral of values for the back-reflection, and using the integrals to determine optimum focus.

Abstract: An optical assembly comprising a plurality of inputs comprising optical fibres which have a non-circular core cross-section, the fibres having a proximal end for receiving light from a respective diode emitter and a distal end, the fibres being combined at their distal ends and joined to a single output fibre which has a circular core cross-section, whereby in use light from a plurality of diode emitters is combined and output through the single output fibre.

Abstract: A termination for an optical fibre is disclosed, including an end cap optically connected to a delivery end of the fibre and tapering its towards its proximal end so as to expand the signal beam output by the fibre, a capillary having a bore mounted so that the end cap and an end portion of the delivery fibre are mounted within the bore, the capillary having an end which is angled so as to reflect undesired radiation within the capillary away from the fibre, and a cladding mode stripper arranged upstream of the delivery end.

Abstract: A diode pumped laser is disclosed having a CW level and adapted to output one or more pulses having peak power greater than the CW level thereby to provide higher peak power for use in material piercing or penetrating operations without affecting diode lifetime.

Abstract: An optical fibre laser or amplifier device is disclosed, comprising: a rare-earth-doped multi-clad optical fibre having at least three cladding layers, one or more multimode pump laser diodes, and a means of multiplexing a laser signal and the pumping radiation, adapted so that a fraction of the stray signal light originating within the device is captured by one of the intermediate cladding layers of the rare-earth-doped fibre and guided out of the laser structure through the multiplexing system resulting in a reduction in the amount of stray signal radiation impinging upon the pump laser diodes.

Abstract: A fibre laser system is disclosed comprising an optical fibre, a part of which is doped with a rare earth to form an optical gain medium; at least one laser diode; means for applying pump radiation from the laser diode to the optical gain medium and for generating a laser beam and delivery fibre means for delivering a laser beam to a workpiece, wherein the fibre laser is provided with at least one means for protecting one or more components from damage caused by errant radiation. Several different means of protection are disclosed.

Abstract: A device for coupling multimode pump light and a laser signal into or out of a cladding-pumped fibre laser is disclosed, comprising an output optical fibre, a substantially un-tapered feed-through optical fibre, an annular waveguide having a tapered section, and a plurality of multimode pump fibres such that: the signal feed-through fibre is located within the annular waveguide; the signal feed-through fibre is fused into the annular waveguide in the tapered section so that the annular waveguide becomes an additional cladding layer of the feed-through fibre; the end of the feed-through fibre that is fused into the annular waveguide is optically coupled to the output optical fibre; the multimode pump fibres are optically coupled to the annular waveguide in the un-tapered section. Methods of forming the device are also disclosed.