Ensenada Center for Scientific Research and Higher Education

This article presents a novel approach to designing and interrogating a large-scale interferometric fiber-optic sensor network by combining correlation-domain and frequency-domain reflectometry. By specially arranging low-reflective Fabry-Perot fiber interferometers within short fiber segments resolved in the correlation-domain and using a secondary layer of demultiplexing in the frequency domain, the system allows for a significant increase in sensor density and increases multiplexing capacity in a long sensing fiber. The measurement system features a cost-effective optoelectronic design that uses an inexpensive, low-power, continuous-wave (CW) telecommunication DFB diode laser, two low-frequency photodetectors, and standard passive fiber-optic components. Digital signal processing enables both the demultiplexing of sensor signals and phase demodulation for static and dynamic perturbations. Experimental validation is provided using a serial array of three interferometers, demonstrating accurate spatial localization and spectral recovery of individual sensor signals. Analytical estimates and numerical simulations suggest a potential multiplexing capacity of several hundred interferometers. The technique is highly configurable, supporting the measurement of arbitrary vibration waveforms, including high-amplitude quasi-static perturbations (with frequencies below the sweep rate) as well as perturbations with frequencies significantly exceeding the sweep rate. Overall, the proposed approach offers a practical and scalable alternative for applications where high interrogation costs have limited the broader adoption of optical sensing technologies.

We present the theory and experimental realization of a quantum polarization-displacement receiver for photonic communications with laser coherent states modulated in their polarization degree of freedom, employing an unconditionally polarization-nulling photon counting scheme. We describe the quantum detection analysis for Polarization Shift Keying (PolSK) modulation formats with laser coherent states, deriving their theoretical performance bounds in error probability and mutual information; and we propose a receiver structure based on a polarization-displacement technique, inspired on the conventional quadrature-displacement schemes employed in the reception of Phase Shift Keying (PSK) modulation formats. Experimentally, we implement our coherent states receiver in a polarization-nulling configuration, employing linear optics for the polarization rotations and displacement, with photon counting at the telecommunications wavelength of 1550 nm, and performing post-detection count–to–voltage operations and logical decision with optimized photon number thresholds; additionally, as a reference, we also implement a quadrature-nulling receiver for a binary PSK format. We perform measurements on the symbol error probability of our receiver, as a function of the photon number of the received photonic signal, finding good agreement with the theoretical estimation at low photon numbers. This receiving structure has advantages over the conventional polarization-splitting and separate photon counting schemes, which is of interest in quantum communications, quantum cryptography and other fields in quantum information.

Dengue is a major mosquito-borne viral disease with no effective antiviral treatment currently available. This work introduces a machine-learning framework to predict anti-dengue activity in small molecules using Atomic-Weighted Vector (AWV) descriptors and data-balancing techniques. Sixteen datasets, each containing 2118 molecules, were generated with MD-LOVIs (Molecular Descriptor from Local Vertex Invariants) and preprocessed with IMMAN (Information theory-based CheMoMetric ANalysis), with Shannon entropy applied for feature selection. To address class imbalance (imbalance ratio = 6.66), the ADASYN algorithm was employed. Thirty classifiers spanning six methodological families were evaluated under two validation schemes (tenfold cross-validation and percentage split) on both balanced and imbalanced datasets. Performance was assessed using accuracy (ACC). Nonparametric statistical tests (Friedman, Nemenyi, Wilcoxon) indicated that data balancing improved model robustness. Tree-based and function-based classifiers achieved the best predictive performance. Overall, the proposed workflow offers a reproducible, data-driven approach for virtual screening of anti-dengue compounds and is readily extensible to other antiviral drug discovery tasks.

In this work, we present the design, fabrication, and study of the optical properties of multilayered metal–dielectric Au/TiO2 structures. The samples were fabricated using Joule effect evaporation for gold and electron beam evaporation for titanium dioxide. Their structure was designed to have an epsilon-near-zero (ENZ) point at different wavelengths around 800 nm, in order to study their nonlinear response as a function of the resonance conditions around the ENZ point. The characterization of the linear properties of the samples was done using spectrophotometry and spectral ellipsometry. We studied the nonlinear response with the z-scan technique at different incident irradiances using a Ti:sapphire femtosecond laser, enabling us to characterize both the refractive and absorptive contributions to the nonlinear response. Due to the high pulse repetition rate inherent to Ti:sapphire systems and the presence of linear absorption in the samples, cumulative pulse-to-pulse thermal effects may be present. A modified version of the z-scan technique that allowed us to separate the electronic from the thermal contribution was used. A clear enhancement of the nonlinear response was observed for the sample with an ENZ point around the laser wavelength 800 nm with a nonlinear refractive index of n2 = 0.103 ± 0.006 cm2·GW−1, a value that is comparable to other ENZ materials in literature.

Children with Autism Spectrum Disorder (ASD) often experience difficulties with tactile sensory processing, which can hinder their participation in daily activities and therapeutic interventions. To address this challenge, we introduce Twinkle Trace, a haptic interface designed to support engagement in classroom-based sensory activities. The system combines a crayon-like stylus, a tablet application to simulate crayon rubbing on textured surfaces using customizable vibration patterns inspired by familiar fruit textures: smooth (apple), rough (melon), bumpy (corn), sharp (pineapple) and adhesive (banana). Twinkle Trace includes a variety of interactive activities, such as free drawing, shape coloring, tactile scene coloring, tracing, and bubble popping, commonly used to promote sensory and fine motor control. We conducted a four-week classroom deployment study with six children with ASD using a comparison within-subjects against traditional crayon rubbing on textured surfaces. Therapist-rated engagement scores showed consistent directional trends favoring Twinkle Trace sessions over traditional activities, particularly in satisfaction, completion, and transitioning. Therapists progressively integrated the tool into daily routines, adapting it to weekly themes and individual needs. These findings suggest that embedding vibrotactile feedback within structured classroom exercises is associated with increased engagement and therapist appropriation in real-world special education contexts. Twinkle Trace provides a classroom-ready haptic system that integrates digital texture generation with therapeutic interaction design.