José Antonio García-Merino

Bioglass (BG) thin films are promising materials for integrating bioactivity with dynamically tunable optical functionality. Here, BG coatings containing two, four, and six deposited layers were fabricated by spin coating to investigate how deposition-dependent changes in thickness and micro/nanostructural organization relate to the thermo-optical response. Film thicknesses were estimated to be 348, 667, and 1061 nm for BG2, BG4, and BG6, respectively. SEM analysis revealed exposed nanorod-like structures in BG2, whereas increasing the number of layers produced thicker and more consolidated porous architectures. The thermo-optical modulation was experimentally investigated using a cross-polarized transmission setup with a 1064 nm pump beam. All samples displayed comparable photothermal dynamics over the investigated irradiance range. However, their optical modulation showed different temperature dependences, with quadratic trends for BG2 and BG4 and an approximately linear trend for BG6. Differences between optical and thermal dynamics can be associated with nonlinear polarization-sensitive detection, thermal gradients, and thermoelastic or scattering contributions. These results suggest that nanostructured domains, porous morphology, and film–substrate interfaces influence the thermo-optical modulation of BG films. The findings motivate further investigation of these coatings for potential biotechnological photonic applications.

Porous multi-walled carbon nanotube (MWCNT) films combine strong optical absorption with thermal, Kerr-like, thermo-optical, and magneto-optical responses. However, these effects depend on film structure and may require different design conditions. In this work, a multiphysics model was used to analyze 12 MWCNT film configurations with dependance on thicknesses, porosity, and orientation parameters. The model included optical attenuation, transient heating, nonlinear refraction, thermo-optic modulation, magneto-optical response, and optical phase shift under irradiances of 7–20 MW cm⁻² and magnetic fields up to 1 T. Optical density ranged from approximately 0.4 to 2.8, while transmittance showed negligible variation with irradiance. Thin and porous films produced the highest temperature rises, approximately 4.5 K, and the largest total refractive-index changes. In contrast, thicker films generated larger accumulated phase shifts. The thermo-optic contribution is dominated under nanosecond laser irradiation. As the pulse duration approached the picosecond regime, the lower deposited energy reduced the photothermal response, so the Kerr-like and magneto-optical terms accounted for a larger total refractive-index change. This predictive parametric study identifies architecture- and pulse-dependent trends for future experimental evaluation of multifunctional MWCNT films.

Photothermal heating can distort Raman baselines and band intensities in aqueous sensing, particularly under 532 nm excitation, and requires explicit thermal modeling for reliable analysis. Here we report a chaos-assisted photothermal Raman framework to probe Pb(NO3)2-spiked water matrices, including residual water collected from La Requena dam (Tepeji del Río, Hidalgo, Mexico). Steady-state Raman spectra were acquired at 532 nm and compared across three conditions: unspiked residual water, ultrapure water with 12 ppm Pb(NO3)2, and residual water with 12 ppm Pb(NO3)2. In parallel, a nanosecond Nd:YVO4 pulsed laser at 532 nm (2–7 µJ, 10 ns, 10 kHz) combined with a focus-tunable lens generated chaotically modulated irradiance; the resulting photodetector time series were analyzed through Newton–Leipnik attractors and single-sided FFT spectra. Fractional Newton cooling fits RMS envelopes quantified thermal memory via the fractional order alpha, which decreased systematically from unspiked residual water to Pb(NO3)2-spiked ultrapure water and Pb(NO3)2-spiked residual water. A linear detector calibration established the working range and uncertainty used in the chaotic and fractional analyses. These results show that chaotic attractor metrics and fractional cooling parameters provide a robust dynamical readout of Pb(NO3)2- and matrix-induced changes in photothermal behavior, enabling practical operating conditions for Raman measurements in complex water samples. These findings provide a quantitative link between chaotic photothermal dynamics and Raman readouts for Pb(NO3)2-related perturbations in residual water.

This work presents a preliminary study using an opto-mechatronic system to measure the refractive index and thermo-optical behavior of blood plasma. The setup employs a 650 nm laser and a displacement sensor on a linear actuator to detect beam deviation through small fluid volumes. Using water-based fluids with different glucose levels, a linear decreasing trend in refractive index with temperature was observed. Furthermore, plasma samples with different glucose concentrations were evaluated across a temperature range. One sample, corresponding to a markedly elevated glucose level, exhibited a dual thermo-optical response that suggests a transition to a different optical regime influenced by complex biomolecular composition. To contextualize these findings, numerical modeling under high irradiance was incorporated as a conceptual framework to explore how thermo-optical properties may evolve under stronger light-matter interactions. The simulations indicate that both glucose concentration and molecular polarizability can modulate the thermo-optical coefficient under nonlinear conditions. Rather than demonstrating molecular specificity, these results serve as initial evidence that optical parameters are sensitive to plasma composition and may guide future studies aimed at establishing selective, light-based biochemical analysis.

Modeling elementary diffusion processes in nanostructured materials is essential for developing platforms capable of interacting with high-speed physical signals. In this work, the photothermal response of a nano-hydroxyapatite/carbon nanotube (nHAp/CNT) composite was experimentally characterized and modeled through a cellular automaton (CA) framework designed to capture the thermal propagation of the hybrid system. Synthesizing nHAp/CNT composites enables the combination of the biocompatible and piezoelectric nature of nHAp with the enhanced photothermal response introduced by CNTs. UV–Vis reflectance measurements confirmed that CNT incorporation increases the optical absorption of the ceramic matrix, resulting in more efficient photothermal conversion. The composite was irradiated with a nanosecond pulsed laser, and the resulting thermal transients were compared with CA simulations based on a D2Q9 lattice configuration. The model accurately reproduces experiments, achieving R² > 0.991 and NRMSE below 2.4% for all tested laser powers. This strong correspondence validates the CA approach for predicting spatiotemporal heat diffusion in heterogeneous nanostructured composites. Furthermore, the model revealed a sensitive thermal coupling when two heat sources were considered, indicating synergistic enhancement of local temperature fields. These findings demonstrate both the effective integration of CNTs within the nHAp matrix and the capability of CA-based modeling to describe their photothermal behavior. Overall, this study establishes a computational–experimental basis for designing controlled thermal-wave propagation and guiding future multi-frequency or multi-source photothermal mixing experiments.