Abstract: Apparatus for optically isolating a laser (1) from external reflections, which apparatus comprises a mode filter (19) and a first optical fibre (1), wherein: the first optical fibre (1) is a multimode optical fibre that supports a fundamental mode (3) and at least one higher order mode (4); the mode filter (19) is defined by an optical attenuation which is higher for the higher order mode (4) than for the fundamental mode (3); the mode filter (19) is configured to pass the fundamental mode (3) into the first optical fibre (1); and the apparatus being characterized in that: the first optical fibre (1) comprises a long period grating (10); and the long period grating (10) is defined by a period (13) selected to couple the fundamental mode (3) to the higher order mode (4) of the first optical fibre (1); whereby if the fundamental mode (3) and the higher order mode (4) are reflected back into the first optical fibre (1) as back-reflected fundamental and higher order modes (25), (26), then the mode filter (19) opt

Abstract: Apparatus for optical isolation, which apparatus comprises a laser (1), a beam delivery system (91), and an output port (92), wherein: the beam delivery system (91) comprises an optical isolator (8) and an optical fibre (2); the laser (1) is defined by a peak power (21); the laser (1) emits laser radiation (13) at a signal wavelength (19); the laser radiation (13) is coupled from the laser (1) to the output port (92) via the beam delivery system (91); and the optical fibre (2) comprises an optical waveguide (100) defined by a core (101), a cladding (102), a mode field area (104) at the signal wavelength (19), a length (86), and a Raman wavelength (25); and the apparatus being characterised in that: the Raman wavelength (25) is longer than the signal wavelength (19); the beam delivery system (91) attenuates the laser radiation (13) at the signal wavelength (19) such that the power of the laser radiation (13) emitted by the laser (1) is more than the power of the laser radiation (13) at the output port (92); th

Abstract: Apparatus for laser welding a first metal part (1) to a second metal part (2), which apparatus comprises: a laser (3) which emits a laser beam (6) in the form of laser pulses (21), a scanner (4) for moving the laser beam (6) with respect to a metal surface (7) of the first metal part (1), an objective lens (5) which focuses the laser beam (6) onto the metal surface (7), and a controller (12) which controls the scanner (4) such that it moves the laser beam (6) with respect to the metal surface (7) to a plurality of focussed spots (16), characterised in that the apparatus focuses the laser pulses (21) with a spot size (34) and a pulse fluence (36) that causes the formation of a plurality of melt pools (19) in the first metal part (1) and heat stakes (17) in the second metal part (2), each heat stake (17) extends from a different one of the melt pools (19) and has a distal end (101), and the controller (12) spaces the focussed spots (16) apart by a distance (18) that is small enough to cause the melt pools (19)

Abstract: An optical fibre (10) which has a first refractive index profile (61) that can be changed by heating to a second refractive index profile (62), at least one first dopant (7) for providing the first refractive index profile, at least one concealed dopant (8), and at least one mobile dopant (9), wherein the mobile dopant has a molar refractivity and is present in a concentration (19) such as to balance a change (146) in the first refractive index profile induced by the concealed dopant, and has a diffusion constant (16) greater than a diffusion constant (15) of the concealed dopant, so that heating of the optical fibre causes the mobile dopant to diffuse more quickly than the concealed dopant, thereby allowing the concealed dopant and the mobile dopant to change the first refractive index profile to the second refractive index profile.

Abstract: Apparatus for providing optical radiation (1), which apparatus comprises a laser diode (2), a pulse generator (9), and a modulator (5), wherein: the pulse generator (9) is configured to emit picosecond pulses; the modulator (5) is configured to emit nanosecond pulses; the laser diode (2) has a first terminal (6) and a second terminal (7); the pulse generator (9) is connected to the first terminal (6); and the modulator (5) is configured to bias the laser diode (2) below a lasing threshold (8) of the laser diode (2), and the apparatus being characterized in that: the modulator (5) is connected to the second terminal (7); the pulse generator (9) comprises a semiconductor junction (32) connected to a differentiator (4); the semiconductor junction (32) is such that electric current flowing through the semiconductor junction (32) can be turned off more quickly than it can be turned on; and the differentiator (4) is such that a step change that occurs when the electric current flowing through the semiconductor junc

Abstract: An apparatus for combining optical radiation, wherein the apparatus comprises a bundle of input optical fibers formed of glass, a taper, and an output optical fiber, wherein the taper is fused to the output optical fiber; and the apparatus comprises at least one cladding mode stripper to strip out higher order modes that would otherwise degrade a polymer coating on at least one of the input optical fibers and the output optical fiber.

Abstract: An optical combiner (25), comprising a bundle of input fibers (24) spliced to an output fiber (26), the output fiber having a cladding and at least one high-index portion within the cladding, such that the high index portion has a diameter substantially equal to or less than the outer diameter of the input fiber bundle at the splice point.

Abstract: A method for laser marking an anodized metal surface (5) with a desired color, which method comprises: providing a laser (1) for emitting a laser beam (4) comprising laser pulses having a pulse energy, a pulse width, and a pulse repetition frequency; providing a scanner (2) comprising a first mirror (6) for scanning the laser beam in a first direction (8), and a second mirror (7) for scanning the laser beam in a second direction (9); providing a lens (3) for focussing the laser beam from the laser (2) onto the anodized metal surface (5) to form a spot (31) having a spot diameter and a pulse fluence; providing a controller (11) for controlling the scanner (2) with a control signal (12); marking a plurality of lines (15) separated by a hatch distance (19) on the anodized metal surface to form a desired mark (16) by scanning the scanner (2) while pulsing the laser (1); selecting a scan speed (16), the pulse repetition frequency, and the spot diameter such that the separation (18) between consecutive spots (31) d

Abstract: A method of optimizing the focus of a fibers laser is described, which comprises positioning the output of a fibers 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: A method for laser marking a metal surface (5) with a desired colour, which method comprises forming at least one first pattern (41) on the metal surface (5) with a first laser beam (42) having a first pulse fluence (43), forming at least one second pattern (51) on the metal surface with a second laser beam (52) having a second pulse fluence (53), characterized by causing the second pattern (51) to overlay the first pattern (41), arranging the first pulse fluence (43) to be at least five times greater than the second pulse fluence (53), the colour being given by the first and second pulse fluences (43, 53) and spot spacings (48) in the first and second patterns (41, 51), and selecting the first and second pulse fluences (43, 53) and the spot spacings (48) to form the desired colour.

Abstract: Apparatus comprising a source of optical radiation (15), an optical fibre (1), and an absorbing material (2), wherein; the optical fibre (1) comprises a core (37), at least one cladding (38), and an optical surface (3); the source of optical radiation (15) provides optical radiation (16) that propagates along the core (37) of the optical fibre (1), and unwanted optical radiation (14) that propagates along the cladding (38) that surrounds the core (37); and the absorbing material (2) is in contact with the optical surface (3) over a length (5) of the optical fibre (1).

Abstract: Apparatus for laser processing a material (8) with optical radiation (T), which apparatus comprises a seed laser (1) pumped by a seed pump (2), an amplifier (3) pumped by an amplifier pump (4), a controller (5), and a scanner (6), wherein the controller (5) controls the seed pump (2), the amplifier pump (4) and the scanner (6) in synchronism such that optical pulses (10) emitted by the seed laser (1) are propagated through the amplifier (3) and directed to the material (8) by the scanner (6), the apparatus being characterized in that controller (5) controls the amplifier pump (4) to cause the amplifier (3) to act as an optical attenuator when the optical radiation (7) is in a first power range, and as an optical amplifier when the output power is in a second power range.

Abstract: Apparatus for providing optical radiation includes a pump source and at least one first amplifying waveguide. The first amplifying waveguide emits optical radiation in excess of 1400 nm when pumped by the pump source. In one embodiment, the pump source can include a plurality of laser diodes and a plurality of second amplifying waveguides. In this arrangement the first amplifying waveguide is pumped by the second amplifying waveguides, the second amplifying waveguides are pumped by the laser diodes, and the second amplifying waveguides are configured to improve the beam quality of radiation emitted by the laser diodes.

Abstract: Apparatus for providing optical radiation, which apparatus comprises an optical fibre (5) having a core (3), a first cladding (1) and a second cladding (2), in which the first cladding (1) has a substantially constant diameter (9) in its cross-section. The first cladding (1) can be non-circular. Advantages include more reliable cleaving, joining and splicing.