Improving the beam quality of solid-state systems using both outside and inside cavity devices with variable optical characteristics along the cross section

This paper presents the results of application to different laser installations of soft or apodized apertures (AA) 1–3] with smooth transmission profiles decreasing from center to edges. Two types of AA, which were made of CaF₂:Pr crystals, have been used: induced absorption (IA) AA and photooxidation (PhO) AA. The 3–45-mm-diameter IA and PhO AA with smooth monotonic flat-top profiles have been used in 1.06-m laser amplifier systems to suppress hard-edge Fresnel diffraction rings in beam cross section and to increase the second harmonic conversion efficiency. The 3–4-mm-diameter PhO AA with bell-like transmission profiles were placed inside the 2.94-m and 1.06-m resonators of master oscillators. The tendency of the output energy to increase by 1.3–1.8 times and the decrease in beam divergence in single-mode lasing as compared with a hard-edge aperture have been observed in the experiments described below.Institute of Radioengineering and Electronics, Academy of Sciences of the USSR. Institute of General Physics, Academy of Sciences of the USSR. Translated from Preprint No. 17 of the Institute of General Physics, Moscow, 1991.