Optical amplifier comprising an end pumped zig-zag slab gain medium

摘要

An optical amplifier (20, 100) includes an elongated slab (22, 102) of solid state lasing material, such as a rare earth doped yttrium-aluminum-garnet (YAG) slab. In order to provide a relatively increased absorption length and thus a higher overall efficiency, the optical amplifier (20, 100) in accordance with the present invention incorporates end pumping in which the pumped light is coaligned with the amplified light resulting in relatively longer absorption lengths and higher overall efficiencies. The coaligned pumped sources are directed to lateral faces of the slab (22, 102) which include footprints (41, 43, 108) or windows. In order to cause internal reflection of the pump beam along the lasing axis, the end faces (28, 30, 110) are formed at about a 45° angle relative to the longitudinal axis which causes the pumped light to be reflected within the slab co-axially with amplified light. In order to confine the absorption of the pumped light to the center portion of the slab (22, 102), the slab (22, 102) may be formed from a composite material with the opposing end portions of the slab formed from an undoped host material while the center portion of the slab along the longitudinal axis is formed from a doped host material. Such a configuration provides relatively low residual thermal lensing with virtually no birefringence. In one embodiment, the pumping light from the diode arrays is coupled to the slab (22, 102) by way of lenses (54) or lens ducts (FIG. 1). In an alternate embodiment, the pumping light is coupled to the slab (22. 102) by way of optical fibers (104, 106). In yet another embodiment (FIG. 8), the pumping light and laser beams are interchanged forming a low-loss straight through slab with end pumped architecture.