A.M.Zabelin

The invention can be applied at making high-power lasers with axial pumping of active medium and beam high quality.

The invention problem is to increase beam quality, output power and efficiency of the laser, and also, to simplify laser construction.

The problem is solved by that the laser active medium is pumped through the tubular excitation chamber, including the optical resonator, having an axis, parallel with axes of the tubular excitation chamber. The end mirrors and the tubular chamber are executed with rectangular or elliptic section, while the resonator is executed stable-unstable (stable in one plane and unstable in perpendicular to it plane). The unstable plane is parallel with the major side (or major ellipse axis) of tubular excitation chamber. The size of the smaller side (smaller ellipse axis - b) is selected, based on that it in 1,5-2 times would exceed the size of the basic mode in the resonator stable plane.