Abstract: An active optical fibre, including: a core; an inner cladding substantially surrounding the core, whereby the core and the inner cladding form an area configured to propagate pump radiation; an outer cladding comprised of at least a third material with at least a third refractive index substantially surrounding the inner cladding, the third refractive index being smaller than the second refractive index, whereby the outer cladding confines pump radiation to the core and the inner cladding; and a coating comprised of a thermally conductive material substantially surrounding the outer cladding, wherein the inner cladding is configured to reduce impact of spatial hole-burning on absorption of the pump radiation as the pump radiation propagates through the active optical fibre, and wherein the thermally conductive material of the coating supports a reduced temperature increase between the area and an outer surface of the coating.

Abstract: A fiber gain medium provided by a rare-earth doped fiber (10) is contained in a first resonant cavity by end reflectors (12, 18). The reflector (12) is wavelength selective to limit the frequency band of the first resonant cavity. The first resonant cavity also contains a second resonant enhancement cavity (16) with multiple transmission bands lying within the first resonant cavity's frequency band. Multiple standing wave modes of the first resonant cavity lie within both the frequency band of the first resonant cavity and the transmission bands of the second resonant cavity, and it is these standing wave modes that support laser action when the rare-earth doped fiber is suitably pumped by pump lasers (40).

Abstract: A laser device comprising a pump source (10) operable to generate a pump beam (11) for a resonant cavity in which a laser medium (74) is arranged. A beam-shaping waveguide element (18) is arranged between the pump source and the resonant cavity. Shaping of the pump beam is achieved by tailoring the refractive index profile of the waveguide element (18) so that it yields an intensity distribution which spatially overlaps a desired ring-shaped Laguerre-Gaussian mode of the resonant cavity sufficiently well to achieve laser oscillation on said desired Laguerre-Gaussian mode. A ring-shaped or doughnut-shaped laser beam profile can thus be generated. It is further possible to design the refractive index profile (76) so that the pump beam's intensity distribution also spatially overlaps the fundamental mode of the resonant cavity sufficiently well to achieve laser oscillation also on said fundamental mode. The laser will then lase on both the fundamental mode and the selected Laguerre-Gaussian mode.

Abstract: Apparatus for providing optical radiation (10) comprising a pump array (8) for providing pump radiation (7), a first pump combiner (1), and a waveguide (3), wherein the pump radiation (7) from the pump array (8) is coupled into the waveguide (3) via the first pump combiner (1), and wherein the waveguide (3) comprises a pump guide (4) for guiding the pump radiation (7), and a gain medium (5) which emits the optical radiation (10) when it is pumped by the pump radiation (7).

Abstract: Apparatus for providing optical radiation (10) comprising a pump array (8) for providing pump radiation (7), a first pump combiner (1), and a waveguide (3), wherein the pump radiation (7) from the pump array (8) is coupled into the waveguide (3) via the first pump combiner (1), and wherein the waveguide (3) comprises a pump guide (4) for guiding the pump radiation (7), and a gain medium (5) which emits the optical radiation (10) when it is pumped by the pump radiation (7).

Abstract: An optical coupler for coupling a signal light beam from a signal port (100) and a pump light beam from a pump port (110) into a common port (120) for coupling the pump and signal beams into a double-clad (DC) optical fiber (122) comprising a core (123), an inner clad (124) and an outer clad (125). The DC optical fiber has a section of coreless fiber (128) joined to it to form an extension piece. A free-space optical arrangement (130) combines the pump and signal light beams onto the common port so that the signal light beam is focused onto the core aperture at the buried interface (121) between the DC optical fiber and the coreless extension piece. The high power density signal beam focus is thus moved away from a more sensitive air:glass interface into a buried interface which has a higher damage threshold. In this way, higher signal beam powers can be handled. The invention allows higher power DC pumped amplifiers and lasers to be fabricated.

Abstract: A beam shaping device for a laser device is provided. The laser device has a beam with a first beam quality factor M.sub.x.sup.2 in a first direction, and a second beam quality factor M.sub.y.sup.2 in an orthogonal direction. The beam shaping device includes at least one reflecting surface diverting at least a first part of the beam in order to reconfigure at least one of the first and second beam qualities M.sub.x.sup.2 and M.sub.y.sup.2.