POSITIVE-BRANCH UNSTABLE RESONATORS WITH THERMAL LENS COMPENSATION

In order to compensate for thermal lensing in Nd:YAG rod active media, placed in unstable resonators with a super-Gaussian reflectivity prof ile of the output mirror, a deformable thin glass plate was used as th e rear mirror. Unstable resonators with a magnification of M = 1.8 and with one and two Nd:YAG rods inside were investigated. By a proper va riation of the radius of the thin glass plate, the magnification of th e resonator was maintained constant by varying the refractive powers o f the rods. For compensated resonators, the output energy of the laser working at 10 Hz repetition rate and pump energies up to 50 J per pul se was close to those obtained for a 1 Hz repetition rate. Copyright ( C) 1996 Elsevier Science Ltd.