ALLAN BERECZKI
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Artigo IPEN-doc 27332 Three-level Nd:YLF Raman laser directly pumped by a beam shaped diode bar2020 - BERECZKI, A.; PAES, JOAO P.F.; WETTER, NIKLAUS U.Low heat generation can be obtained when pumping Nd:YLF at wavelengths of 872 nm and 880 nm and emitting at the three-level transition of 908 nm. These transitions show very low quantum defect with efficiencies of 0.96 and 0.97, respectively. However, the low average absorption cross-section at these wavelengths makes efficient absorption even for longitudinal pump setups difficult. Using a beam-shaped pump diode instead of a fiber-coupled diode bar may be an effective means of increasing absorption because it can provide for π-polarized radiation which shows higher absorption cross section. In this work, a Nd:YLF was pumped at 872 nm by a diode bar using beam-shaping. Results were compared to pumping at 872 and 880 nm with non-polarized fiber-coupled diodes. Stimulated Raman scattering was also obtained with a KGW crystal generating first Stokes emissions at 990 nm and 976 nm.Artigo IPEN-doc 27331 Dynamically stable lasers from commercial Nd:YAG modules with high beam quality and single-frequency2020 - BERECZKI, A.; WETTER, NIKLAUS U.Diode-side pump Nd:YAG rod modules are widely available, reliable and commercially very attractive for building continuous-wave solid-state lasers in the 10-1000 W range. Newer technologies such as fiber or thin disk lasers are generally much more expensive but have the benefit of better beam quality and higher output powers if necessary. By using well-known techniques for designing dynamically stable resonators (DSRs), lasers with high extraction efficiency and high beam quality (fundamental mode, TEM00) can be obtained also with diode side-pumped modules. However, a successful project for a dynamic stable laser depends critically on the correct choice of the fundamental mode diameter within the rod. DSR design rules are based on the beam waist, w3, at the rod principal planes by considering the rod as a thin thermal lens, which differs significantly from real resonators. Here we give guidelines and criteria on how to establish the correct diameter in each case. Using off-the-shelf 75 W Nd:YAG modules it was possible to obtain linearly polarized TEM00-mode output of 30 W with M2=1.08 from a single module, M2=1.2 and 76.5 W of output power using two modules and 100.5 W of polarized, continuous output with M2=1.8. A single-frequency ring laser was also built, using two modules, generating 51.6 W of fundamental wave single-frequency output.Artigo IPEN-doc 26080 Dynamically stable continuous single frequency green ring laser2019 - BERECZKI, ALLAN; WETTER, NIKLAUS U.; CRUZ, FLAVIO C. daA single-frequency ring laser using two standard commercial diode-pumped Nd:YAG modules is demonstrated. Employing a dynamically stable resonator design, multi-longitudinal mode operation at 1064 nm with 53 W of output power was obtained. When inserting a LBO crystal in the resonator, 1.8 W of single-sided, single-frequency output at 532 nm was achieved. The measured linewidth was 3.6 MHz, close to the resolution limit of the scanning etalon used to measure the longitudinal mode structure.