ALLAN BERECZKI
19 resultados
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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 30048 Micro-Raman spectroscopy identification of hydroxyapatite in dental pulp stem cells2023 - SILVA, FLAVIA R.O.; PASCOAL, DIEGO R.C.; BERECZKI, ALLAN; SIPERT, CARLA R.; BRAGA, ROBERTO R.; BELLINI, MARIA H.; SILVA, LUIS F.T.; FREITAS, ANDERSON Z.; WETTER, NIKLAUS U.Cell differentiation using calcium phosphate nanoparticles was studied. The hydroxyapatite was internalized in human dental pulp stem cells and characterized by Raman spectroscopy. Raman spectra showed the hydroxyapatite distribution in nanoparticles nodules in the cells.Artigo IPEN-doc 30047 Direct nanoplastics detection below the diffraction limit using micro Raman2023 - BERECZKI, ALLAN; DIPOLD, JESSICA; FREITAS, ANDERSON Z.; WETTER, NIKLAUSRaman spectra of polystyrene nanoparticles of 50 nm diameter were directly measured using micro-Raman spectroscopy. Data analysis demonstrated that particles as small as 20 nm could be directly measured with this simple and robust technique.Artigo IPEN-doc 30037 Sub-10 nm nanoparticle detection using multi-technique-based micro-raman spectroscopy2023 - BERECZKI, ALLAN; DIPOLD, JESSICA; FREITAS, ANDERSON Z.; WETTER, NIKLAUS U.Microplastic pollution is a growing public concern as these particles are ubiquitous in various environments and can fragment into smaller nanoplastics. Another environmental concern arises from widely used engineered nanoparticles. Despite the increasing abundance of these nanosized pollutants and the possibility of interactions with organisms at the sub cellular level, with many risks still being unknown, there are only a few publications on this topic due to the lack of reliable techniques for nanoparticle characterization. We propose a multi-technique approach for the characterization of nanoparticles down to the 10 nm level using standard micro-Raman spectroscopy combined with standard atomic force microscopy. We successfully obtained single-particle spectra from 25 nm sized polystyrene and 9 nm sized TiO2 nanoparticles with corresponding mass limits of detection of 8.6 ag (attogram) and 1.6 ag, respectively, thus demonstrating the possibility of achieving an unambiguous Raman signal from a single, small nanoparticle with a resolution comparable to more complex and time-consuming technologies such as Tip-Enhanced Raman Spectroscopy and Photo-Induced Force MicroscopyArtigo IPEN-doc 29782 Dynamic stable ring resonator for high-power continuous single-frequency lasers2023 - BERECZKI, ALLAN; WETTER, NIKLAUS U.When considering dynamically stable resonators, ring lasers are good choices because they have a stability interval that is twice as large as that of linear resonators and sensitivity to misalignment decreasing with pump power; however, the literature does not provide easy design guidelines. A ring resonator utilizing Nd:YAG side pumped by diodes allowed single-frequency operation. The output single-frequency laser had good output characteristics; however, the overall length of the resonator did not allow for building a compact device with low misalignment sensitivity and larger spacing between longitudinal modes which could improve single-frequency performance. Based on previously developed equations, which allow for ease of design of a ring dynamically stable resonator, we discuss how to build an equivalent ring resonator, aiming to building a shorter resonator with the same stability zone parameters. The study of the symmetric resonator containing a pair of lenses allowed us to find the conditions to build the shortest possible resonator.Resumo IPEN-doc 29669 Nd:YAG polarized laser with beam quality beyond the birefringence limit and its application in a Singly-Resonant Optical Parametric Oscillator2018 - LOPEZ, MARCIO A.P.A.; BERECZKI, ALLAN; WETTER, NIKLAUS U.We demonstrate a simple, reliable and cheap high output power, linearly polarized and high-quality beam @1064 nm laser source, based on a previous work [i], where a Nd:YAG Diode-pumped Solid-state Laser (DPSSL) based on standard, commercial laser modules was presented. This kind of laser source is interesting for a large number of applications, such as pump laser for an Optical Parametric Oscillator (OPO) and frequency conversion, maintaining near-diffraction-limited beam quality factor (M2~1).Artigo IPEN-doc 29353 Raman Spectroscopy of irradiated and non-irradiated plastics2022 - DIPOLD, JESSICA; BERECZKI, ALLAN; PINHEIRO, GUSTAVO; VASCONCELOS, KAMILLA; FREITAS, ANDERSON Z. de; WETTER, NIKLAUS U.Understanding radiation damage to plastic is of great interest for possible construction applications. Two different plastics were gamma irradiated and their property changes were studied with micro-Raman spectroscopy, showing promising results in increasing its toughness.Artigo IPEN-doc 29350 Compact, high-power, single-frequency, dynamically stable cw ring laser2022 - BERECZKI, ALLAN; WETTER, NIKLAUSWe recently reported a single-frequency Nd:YAG ring laser with 55.6 W CW output. In this work our design equations are given in order to obtain compactness and increasing resonator free spectral range.Artigo IPEN-doc 28755 Adaptive, high-power, dynamically stable ring resonator2022 - BERECZKI, A.; WETTER, NIKLAUS U.Dynamically stable resonators have a stationary TEM00 beam waist inside the laser rod (w30), which is minimal throughout the stability interval and insensitive to changes in pump power. For a given set of resonator parameters (mirror radii and distances between mirrors and rods), the stability interval parameters, which are the limits of the stability interval in terms of the rod’s thermally induced focusing length are determined. In linear resonators, these stability interval parameters cannot be changed independently only by varying resonator distances, and mirrors of different curvature have to be employed. However, our group showed recently that for a symmetric ring resonator containing a pair of curved mirrors, the width of stability interval and the stability interval limit at maximum rod’s focal length can be adjusted continuously and independently only by varying resonator distances once the mirror radius of curvature has been fixed. In this work we demonstrate a project of an adaptive ring resonator that allows the TEM00 - mode resonator to be continuously tuned throughout the whole range of pump powers utilizing standard electromechanics to move the mirrors. Additionally for a given value of pump power, w30 can be varied, thus allowing different beam qualities to be obtained from the same resonator.