A semiconductor laser light source device and light source unit according to the present invention include a first plate-like member made of metal, to which a semiconductor laser array is joined along the end portion, a second plate-like member made of metal, in which an inlet opening portion, which introduces cooling fluid, and a cooling fluid draining channel, and a third plate-like member made of metal, which is formed along the area corresponding to the end portion and to which at least one cooling channel is provided through which cooling fluid flows in the longitudinal direction of the semiconductor laser array by communicating the cooling fluid introducing channel and the cooling fluid draining channel. Thus, the sectional area of the channel can be larger than that in the construction of the related art and the processing cost is reduced by comparison with the construction of the related art. The problems of blocking path with an extraneous matter and of high-pressure loss due to the path are overcome. Since the channel is provided along the longitudinal direction of the semiconductor laser array, the semiconductor laser array can be cooled efficiently.

A solid state laser medium comprising at least one cooling element, i.e. cooling element, in contact with and alternating in series with at least one gain element. At least one cooling element and at least one gain element are joined at an interface having a center point, wherein the interface is physically modified at the interface such that the heat transfer coefficient at the interface decreases radially from the center point of the interface. The modified interface promotes thermal transfer from the gain element in the axial direction, in such a manner as to reduce thermal distortion affecting optical properties of the laser. Concentric radially disposed barriers to heat flow that hinder heat flow in the radial direction may be added within the gain element to further reduce thermal distortion within the laser medium.

An assembly for providing a concentrated, vertically stacked array of laser beams from a horizontally offset array of electrically serially-connected metallic microchannel heat sinks each bearing a laser diode bar. The heat sinks are mounted on horizontally offset planes of the manifold which has coolant channels serving adjacent heat sinks that are separated from each to increase the electrical resistance of the fluid path between adjacent ones of said heat sinks. Stepped optical deflectors re-arrange the horizontally emitted laser beams into vertical stack.

A cooling device suitable for cooling a laser diode bar constituting a surface illuminating device as a light source for exciting a laser medium of a solid-state laser oscillator of high power. The cooling device is capable of flowing coolant at sufficient flow rate by reducing the pressure loss in the flow passage of the coolant in the device, to realize a light source device of small thickness with high cooling capability and high reliability. The cooling device comprises a first plate member, one or more second plate member and a third plate member to be joined together to form a laminated body. The second plate member has grooved paths formed on both surfaces thereof and having depths greater than a half of thickness of the plate member, and also opened paths for communicating grooved paths formed on the first plate member and the third plate member. The pressure loss in the flow passage of coolant is reduced by increasing a sectional area of the flow passage by the grooved paths and the opened path of the second plate member without lowering mechanical strength of the device and without increasing a manufacturing cost of the device.