Abstract: Single- or few-moded waveguiding cladding-pumped lasers, superfluorescent sources, and amplifiers, as well as lasers, including those for high-energy pulses, are disclosed, in which the interaction between the waveguided light and a gain medium is substantially reduced. This leads to decreased losses of guided desired light as well as to decreased losses through emission of undesired light, compared to devices of the prior art. Furthermore, cross-talk and inter-symbol interference in semiconductor amplifiers can be reduced. We also disclose devices with a predetermined saturation power. As a preferred embodiment of the invention, we disclose a single (transverse) mode optical fiber laser or amplifier in which the active medium (providing gain or saturable absorption) is shaped as a ring, situated in a region of the fiber's cross-section where the intensity of the signal light is substantially reduced compared to its peak value. The fiber can be cladding-pumped.

Abstract: Single- or few-moded waveguiding cladding-pumped lasers, superfluorescent sources, and amplifiers, as well as lasers, including those for high-energy pulses, are disclosed, in which the interaction between the waveguided light and a gain medium is substantially reduced. This leads to decreased losses of guided desired light as well as to decreased losses through emission of undesired light, compared to devices of the prior art. Furthermore, cross-talk and inter-symbol interference in semiconductor amplifiers can be reduced. We also disclose devices with a predetermined saturation power. As a preferred embodiment of the invention, we disclose a single (transverse) mode optical fiber laser or amplifier in which the active medium (providing gain or saturable absorption) is shaped as a ring, situated in a region of the fiber' cross-section where the intensity of the signal light is substantially reduced compared to its peak value. The fiber can be cladding-pumped.

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.

Abstract: The invention is based on the discovery that under certain conditions lasing at room temperature can be achieved in a Pr.sup.3+ -doped fluorozirconate fiber pumped in the infrared at 1.01 .mu.m and 835 nm, the lasing taking place in the blue (491 nm), green (520 nm), orange (605 nm) and red (635 nm and 715 nm). One laser comprises a length of Pr.sup.3+ -doped potical waveguide such as a fiber, and means for exciting the Pr.sup.3+ ions to an energy level in the band (.sup.3 P.sub.2, .sup.1 I.sub.6, .sup.3 P.sub.1, .sup.3 P.sub.0), in which the Pr.sup.3+ concentration is in the range substantially 50 ppm to substantially 10,000 ppm (by weight). The Pr.sup.3+ concentration is preferably in the range substantially 200 ppm to substantially 2,000 ppm (by weight). The optical fiber is preferably a fluorozirconate fiber doped at the foregoing concentrations with Pr.sup.3+ ions. The fiber preferably comprises a doped core clad with a further glass. The excitation means is preferably arranged to excite the Pr.sup.