This paper presents a tunable, switchable multi-wavelength emission from an erbium-doped fiber ring laser, enabled by adjusting the spectral fringe visibility of a fiber interferometer filter. The filter is formed with specially designed concatenated tapered fibers to configure a Mach-Zehnder fiber interferometer (MZFI). The laser emission is highly flexible and reconfigurable, allowing for tuning between single- and dual-wavelength operation. The laser can switch sequentially from one up to six wavelengths by fixing the curvature and adjusting the polarization state. The lasing emission is generated over a stable wavelength range between 1559.59 nm and 1563.54 nm, exhibiting an optical signal-to-noise ratio (OSNR) exceeding ~35 dB. The performance of amplitude and wavelength fluctuations were evaluated, indicating an appropriate stability of ~3 dB and a shift less than 0.1 nm within a 45 min period at room temperature. A detailed comparison with the literature is given.

This work reports the obtention of nanocompounds from epoxy resin (EP) with graphenes at three different oxidation degrees (GO1, GO2, and GO3), functionalized with 3-glycidyloxypropyl trimethoxysilane (GPTMS), and three different graphene concentrations (1%, 2%, and 3%). The aim is to improve GO compatibility in EP and obtain a nanocompound with synergistic properties. Ultrasonic bath was used to disperse the GO, a factor in the effective interaction between GO and the polymeric matrix. The nanocompounds were characterized by FTIR, SEM, and mechanical tension testing. The FTIR analysis evidenced stretching bonds created during the functionalization of graphene oxide (GO) with the silane (GPTMS); they are characteristic Si-O-Si and Si-O-C at 1000 and 1085 cm⁻¹, respectively. There was a difference between GO and GO-GPTMS nanocompounds regarding the formation of these signals. The SEM micrographs showed morphological changes when GO was added: the smooth fracture surface of EP became rougher. During tension testing, Young’s modulus (2.09 GPa) of GO2-GPTMS/epoxy nanocompounds (1% weight GO) increased by 35% while their resistance to traction (98.71 MPa) grew by 52%; both were higher than in pure EP. In conclusion, the variables studied (oxidation degrees and silanization) significantly affect the mechanical properties studied.

Massive pelagic Sargassum influxes along Caribbean coasts have created an urgent need for valorization routes for this biomass. Here, sodium alginate was extracted from Sargassum fluitans collected at Chuburná Beach, Yucatán, Mexico, using a multistep extraction involving 0.2% formaldehyde pretreatment at 4 °C and brief heating at 65–70 °C, and subsequently used to prepare calcium-crosslinked alginate nanoparticles by ionotropic gelation. To our knowledge, this is the first direct synthesis of alginate nanoparticles from non-commercial alginate extracted from pelagic S. fluitans. An extraction yield of 18.7 ± 0.05% (mean ± SD, n = 3) was obtained, and UV–Vis, FTIR, and NMR analyses confirmed the characteristic structural features of alginate. ¹H NMR revealed an M-rich composition (F_M = 0.61, F_G = 0.39; M/G = 1.54) with short guluronate blocks (N_G>1 = 2.42), whereas ¹³C NMR corroborated the presence of both β-D-mannuronic and α-L-guluronic acid residues. SEM images showed predominantly spherical-to-subspherical nanoparticles with representative dry diameters of 233–269 nm, whereas DLS measurements at 0, 24, and 72 h revealed a dominant volume-based nanoscale population with main peaks at 12.75–15.31 nm and PDI values of 0.229–0.291, indicating reasonable short-term colloidal stability at room temperature. These results demonstrate that pelagic S. fluitans can serve as a viable feedstock for the production of structurally preserved alginate and calcium-crosslinked alginate nanoparticles. The study supports converting recurrent Sargassum biomass into higher-value polysaccharide-based materials and provides a basis for future application-specific evaluation of these nanomaterials.