ALLAN BERECZKI
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Artigo IPEN-doc 30184 Sub-nanosecond microchip oscillator for a MOPA system tailored for tattoo removal2023 - CATARINA, MARCUS V.; BERECZKI, ALLAN; WETTER, NIKLAUS U.In this work we study a microchip laser designed to function as an oscillator in a Master-Oscillator Power-Amplifier (MOPA) system targeted for laser tattoo removal. Different configurations of the Nd: YAG resonator were used by changing the output coupler mirror reflectivities and the initial transmission of the Q-switch. The quasi-CW resonator provided 55.4 W of output with 51.31% and 78.2% optical and slope efficiencies, respectively. For Q-switched operation, the best configuration resulted in a peak output power of 3.6 MW with 588 ps pulse width.Artigo IPEN-doc 30183 Compact, high power CW ring laser resonator2023 - BERECZKI, ALLAN; MENEZES, FELIPE C. de; WETTER, NIKLAUS U.We demonstrated the dynamically stable operation of aNd: YAG ring laser with 51.8 W of linearly polarized, continuous output power. The laser was based on laser modules side-pumped by diode bars. The resonator, aimed at single-frequency operation, is a design improvement from a previous work with the resonator length 4.3 times smaller than the previous design, thus resulting in a larger free spectral range, favoring for operation at single-frequency.Artigo IPEN-doc 28141 Dynamically stable single frequency ring resonator from diode pumped Nd:YAG modules with 55.6 W of output power2021 - BERECZKI, ALLAN; FERREIRA, AMAURI A.; WETTER, NIKLAUS U.A Nd:YAG rod single-frequency ring laser based on side-pumped commercial modules is presented. Thermally induced birefringence compensation was applied in a dynamically stable resonator providing 55.6 W of continuous, linearly polarized, TEM00 output. The particular case of a symmetric ring resonator containing one or two focusing rods and a pair of curved mirrors was analyzed and a design technique is presented, allowing for easy, continuous shaping of the stability limits by changing only the distances in the resonator.Artigo IPEN-doc 24807 Quasi-three level Nd:YLF fundamental and Raman laser operating under 872-nm and 880-nm direct diode pumping2018 - WETTER, NIKLAUS U.; BERECZKI, ALLAN; PAES, JOAO P.F.Nd:YLiF4 is the gain material of choice whenever outstanding beam quality or a birefringent gain material is necessary such as in certain applications for terahertz radiation or dual-frequency mode-locking. However, for high power CW applications the material is hampered by a low thermal fracture threshold. This problem can be mitigated by special 2D pump set-ups or by keeping the quantum defect to a minimum. Direct pumping into the upper laser level of Nd:YLiF4 is usually performed at 880 nm. For quasi-three level laser emission at 908 nm, direct pumping at this wavelength provides a high quantum defect of 0.97, which allows for very high CW pump powers. Although the direct pumping transition to the upper laser state at 872 nm has a slightly smaller quantum defect of 0.96, its pump absorption cross section along the c-axis is 50% higher than at 880 nm, leading to a higher absorption efficiency. In this work we explore, for the first time to our knowledge, 908 nm lasing under 872 nm diode pumping and compare the results with 880 nm pumping for quasicw and cw operation. By inserting a KGW crystal in the cavity, Raman lines at 990 nm and 972 nm were obtained for the first time from a directly pumped 908 nm Nd:YLF fundamental laser for both quasi-cw and cw conditions.Artigo IPEN-doc 24806 Dynamically stable operation of a 100-watt level CW single frequency ring laser at 1064 nm2018 - WETTER, NIKLAUS U.; BERECZKI, ALLAN; FERREIRA, AMAURI A.For high-resolution spectroscopy, a stable, narrow linewidth and high power output laser is desirable in order to pump different types of resonant optical parametric oscillators, which is the goal of the present work. Typical single frequency pump lasers are in the range of 10 watt output power whereas, depending on application and OPO type, higher power (>20 W) is desirable. Here we demonstrate a high-power single frequency laser based on off the shelf standard Nd:YAG pump modules. Two closely spaced, diode-side-pumped Nd:YAG rods were used in a mode-filling configuration to form a CW polarized ring resonator with TEM00 beam quality and output power of 105 W. The output power achieved is, to our knowledge, the highest reported for continuous polarized, fundamental-mode ring lasers using standard side-pumped Nd:YAG modules. The resonator allowed for power tuning over a large dynamic range and achieved excellent beam quality, using a half wave plate between both rods for birefringence compensation. Single frequency operation was achieved using a TGG crystal and an etalon, with a preliminary output power of 40 W.Artigo IPEN-doc 23152 100W continuous linearly polarized, high beam quality output from standard side-pumped Nd:YAG laser modules2017 - BERECZKI, ALLAN; WETTER, NIKLAUS U.Dynamically stable operation with joined stability zones of a linearly polarized resonator is shown for a laser containing two diode side-pumped Nd:YAG rods. The unpolarized resonator generated 115W of output. When polarized by a Brewster plate, it reached 100.5W of output power at a beam quality M2 < 2. Best measured beam quality was of 1.1 and 1.3 in the x and y directions respectively, with 76W of 95% polarized output. The output power achieved is, to our knowledge, the highest reported for continuous polarized, fundamental-mode lasers using standard side-pumped Nd:YAG modules.