CO or CO.sub.2 Waveguide Laser

The invention is directed to a CO or CO.sub.2 waveguide laser of the sealed-off type having transversal excitation and which contains two metal electrodes that serve as waveguide surfaces which are separated from one another by inserter strips. Such a laser is known from IEEE Journal of Quantum Electronics, Vol. QE 20, No. 3, March 1984, incorporated herein by reference. Two aluminum electrodes of polished aluminum are utilized therein. Just like many other metals, however, aluminum reacts with the oxygen of the plasma of a CO or CO.sub.2 waveguide laser. It has been shown that the oxygen content in a sealed-off laser is thereby steadily reduced over a long time, so that the laser characteristics change and the useful life does not correspond to what was anticipated. The formation of aluminum oxide under the conditions of laser discharge thereby does not lead to a dense, insensitive layer of aluminum oxide, or does not lead thereto in an adequately short time.

An object on which the present invention is based is to enhance a useful life of the laser without loss of quality. This is achieved according to the invention by coating the electrodes with a passivation layer that is insensitive to oxidation by the adjoining plasma, this layer having a low roughness that does not disturb the wave guiding.

Passivated layers of aluminum, chromium, and nickel, i.e. layers of aluminum, chromium, and nickel that no longer noticeably change under the influence of ionized oxygen or laser plasma, or layers of precious metals, particularly gold, platinum, and palladium, are thereby suitable as layers insensitive to oxidation due to the adjoining plasma. These layers can be produced with high quality and high surface smoothness. Given employment of aluminum layers, it is desirable that the aluminum is applied in a form of a highest grade aluminum. A highest grade aluminum can be extremely well-smoothed and, upon oxidation, yields dense and smooth oxide layers that do not negatively influence the waveguide properties. It is therefore precisely these highest grade aluminum layers that are suitable for being passivated by an aluminum oxide layer. This aluminum layer should be less than 1 .mu.m thick so that the unavoidable losses due to the waveguiding are not increased by roughness.

The electrodes are preferably manufactured of easily workable and highly thermally conductive material; in particular, copper or aluminum are suitable. When aluminum alloys are employed as an electrode material, it is desirable that a layer of nickel is first applied thereon; this is then followed by a layer of highest grade aluminum; and the exposed surface of the highest grade aluminum layer is coated with a passivation layer of the above described type. Rough layers that tend to form given aluminum alloys are thus avoided; and layers that are oxidation-resistant over a long time are also achieved.

The waveguide laser is especially advantageously constructed as a slab or ribbon conductor or stripline laser. In such lasers, the wall stressing due to the plasma is relatively high; and the useful effect of the proposed passivation is especially high. An especially cost-beneficial structure can thus be achieved since ceramic strips are soldered in between the coated electrodes, these ceramic strips serving as a lateral limitation of the plasma space and as spacers for electrodes. This in-soldering of the strips is promoted by the applied passivation layers; an additional application of contact layers as are otherwise standard when soldering ceramic parts can be omitted.

The invention shall now be set forth in greater detail with reference to the drawing figures. The invention is not limited to the embodiments shown in the drawing figures.

FIG. 1 is a cross-sectional view of the waveguide laser according to the invention taken along line I--I in FIG. 2; and

FIG. 2 is a plan view of the waveguide laser of the invention.

Two electrodes 1 and 2 of a waveguide laser are provided with passivation layers 3 that adjoin the plasma space 8. Two ceramic strips 4 are soldered in between the passivation layers 3. They are soldered in on the electrodes 1 or 2 and serve as spacers for the electrodes and as a termination of the plasma space 8. The passivation layers 3 are insensitive to oxidation by the plasma in the plasma space 8. As a result thereof, the equilibrium of the ions in the plasma is preserved over a long time. Accordingly, the laser can satisfy the standard demands made of useful life, for example a useful life of five thousand hours.

In the example illustrated in FIG. 2, a ribbon conductor or stripline laser having an unstable resonator is provided. There, the resonator is formed by the mirrors 5 and 6, and a beam exit window 7 is arranged adjoining the mirror 6. The wall stressing in such an intrinsically known laser structure is relatively high, and the advantage of the present invention is especially pronounced.

Although various minor changes and modifications might be proposed by those skilled in the art, it will be understood that we wish to include within the claims of the patent warranted hereon all such changes and modifications as reasonably come within our contribution to the art.