Resumen El Premio Nobel de Física 2021 fue otorgado a Syukuro Manabe, Klaus Hasselmann y Giorgio Parisi por sus "contribuciones innovadoras a nuestra comprensión de los sistemas físicos complejos." Aquí repasamos algunas de las ideas y resultados que sirvieron de base científica al premio. También comentamos los trabajos de nuestro grupo de investigación sobre las propiedades de sistemas complejos de los láseres aleatorios y láseres de fibra aleatorios.

Abstract The 2021 Physics Nobel Prize was awarded to Syukuro Manabe, Klaus Hasselmann, and Giorgio Parisi for their "groundbreaking contributions to our understanding of complex physical systems." Here we review some of the ideas and results which served as the scientific basis to the award. We also comment on the works by our research group on the complex systems properties of random lasers and random fiber lasers.

Samples of (1 – x)SiO2:xGeO2 compositions, containing x = 10 and 20, and doped with Er3+, were prepared by a simple sol-gel route. Homogeneous and transparent gels were synthesized and xerogels were obtained by gel annealing from 700 ºC to 1100 ºC. Films exhibiting high transmittance in the visible and near infrared were deposited by spin-coating technique using the colloidal precursors. The materials were characterized structurally and microstructurally by some techniques. Spherical completely amorphous and tetragonal GeO2 nanocrystals from 3.7 nm to 25.0 nm in diameter embedded in silica-rich amorphous phase materials were obtained. The optical properties were studied by transmission spectra from ultraviolet to near infrared region, photoluminescence measurements in the infrared region, and the average lifetime of the metastable state 4I13/2 of Er3+ ions were determined. The 1 mol% Er3+ doped host with x = 20 have an infrared emission 4.9 times higher than the compound containing x = 10, and the Er3+4I13/2 level present lifetime between 15.0 ms and 7.5 ms. The optical band gap and refractive index values were determined, as well as the Sellmeier parameters. Finally, rib channel waveguides using femtosecond laser etching technique on silica substrates were obtained with width of 15 mm. The 1 mol% Er3+ doped 80SiO2:20GeO2 compounds can be applicable in integrated optical systems.

This study used optical coherence tomography (OCT) compared to scanning electron microscopy (SEM) and optical microscopy (OM) to evaluate qualitatively crack propagation and final fracture in restorative composite materials - Filtek Z250 and Filtek Z350 (3M ESPE) - with fiber reinforcement after cyclic loading. Samples were made using a split mold. Initially, 3-point bending tests were performed to determine the maximum force and tension at the fracture moment using samples without fiber reinforcement. Then, mechanical cycling tests were performed using samples with glass fiber embedded internally. The failures were analyzed using the 3 methods described before. OCT permitted good characterization of internal crack propagation of the dental composites, which, however, could not be visualized by either SEM or OM. OCT was proven to be laboratory research tool that is easy to use, does not require any specific preparation of the samples, and is less expensive than SEM.