ALLAN BERECZKI
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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 24863 Dynamically stable Nd:YAG resonators with beam quality beyond the birefringence limit and pumping of a singly resonant optical parametric oscillator2018 - BERECZKI, ALLAN; LOPEZ, MARCIO A.P.A.; WETTER, NIKLAUS U.A simple, reliable, linearly polarized laser source with very high beam quality is demonstrated using standard diode-side-pumped Nd:YAG modules. The laser produced 30 W of output power with beam quality factor 𝑀2<1.15 over the entire range of input powers and beam quality of 1.02 at the laser operation point. This is, to our knowledge, the highest beam quality for a dynamically stable high-power laser that uses an optically isotropic crystal. The laser was used as a pump source for an optical parametric oscillator based on a periodically poled lithium niobate, producing wavelength in the 1.5–3.8 μm range.