There has already been disclosed in the patent document U.S. Pat. No. 4,378,601 an optically pumped laser having an arrangement for securing the SLAB type bar. This laser comprises essentially a housing intended to receive the bar and in which there circulates a cooling fluid. Additionally, the laser comprises a luminous source arranged on either side of the bar in order to bring about optical pumping in the active medium. The bar is mounted in a securing arrangement which may be introduced into the housing or withdrawn therefrom.
This securing arrangement comprises on the one hand first longitudinal support elements having a U-formed cross-section and which are provided with lugs at their ends, these elements enveloping the upper face and the lower face of the bar and on the other hand second support elements having a configuration complementary to that of the ends of the bar so as to be attachable thereto. The lugs of the first support elements cooperate with slots provided in the second support elements in order to maintain the bar in a rigid frame intended to be installed in a housing.
This securing arrangement has the advantage of rigidly maintaining the bar in the laser without bringing about mechanical stresses in the latter. One thus avoids the risk of having variations of the refractive index in the bar, such variations having as effect an alteration of the quality of the laser beam.
However, this arrangement also gives rise to a difficulty. Effectively, since the bar is totally immersed in the cooling fluid except for its extremities, the lateral faces of the bar are cooled just as the upper and lower faces. Consequently, the temperature gradient following a path which is perpendicular to the upper and lower faces of the bar, varies according to whether this path is close to or remote from a lateral face and this brings about edge effects diminishing the yield of the laser.
Another type of securing means of the bar in a laser described in patent document U.S. Pat. No. 4,761,789 attempts to overcome this difficulty by isolating the lateral faces of the bar from the cooling fluid. This laser comprises a bar placed between two transparent laminae, the bar and the laminae being arranged between two support plates, each of these including a rectangular opening which extends substantially over the length of the bar. Packing gaskets assure sealing around the periphery of the openings between the laminae and the support plates. On these openings there are arranged to be aligned for instance pumping reflectors having substantially a U-form cross-section which, together with the laminae bound a circulation space for a cooling fluid as well as a housing for an optical excitation source for the bar. Finally, between each support plate and the outer framework there is provided a bracing frame bounding a second cooling channel, the assembly being mechanically clamped in order to guarantee good securing of the bar and good sealing.
Nevertheless, the solution suggested by the above mentioned document does not bring about entire satisfaction. Effectively, during the mechanical clamping of the assembly, the clamping effort is not checked with the result that it is very difficult to obtain an appropriate clamping.
If the clamping is too great, one induces mechanical stresses in the bar and there result therefrom variations in the refractive index which change the quality of the beam.
On the other hand, should the clamping be insufficient, the transmission of the quantity of heat through the laminae, the support plates etc. diminishes thereby bringing about a lowering of the laser yield.
The invention thus has as its main purpose to remedy these difficulties arising in the abovementioned prior art by furnishing a laser provided with a securing arrangement for the bar which eliminates the influence of the clamping force while isolating the lateral faces of the bar from the cooling liquid.