Unstable resonator for a laser with a few active media.

At present, many researchers in the leading laser-building companies are involved in solving the problem of creation of high-power industrial lasers. This is conditioned both by increasing demand of industry for such sort of laser devices and by significant achievements in studies of the moderate-power lasers. Besides the high average power, the output beam of 0 a commercial laser must have a small divergence (close to the diffraction limit) and a minimized beam jitter (not higher than the divergence). As is well known, the increase of the average output power of a laser operating in a repetitively-pulsed mode, is accompanied, practically inevitably, by increasing divergence and yawing of the output beam. This universal tendency (Such a dependence of changing specified parameters) is basically caused by instabilities in the laser active media at higher level of pumping and, in this connection, by a less efficient heat removal from the active medium and degradation of optical quality of the active media and resonator components during its operation. Similar problems also arise when the average output power is increased in a straightforward way by direct scaling of the laser systems. In this report, we describe an original configuration of the unstable resonator intended for a high-power repetitively-pulsed laser comprised of several laser heads of moderate power. We show that the beam divergence and yawing of such a powerful laser remain practically at the level of appropriate parameters for the moderate-power lasers, whereas the average output power increases proportionally to a number of the laser heads used.