Angel Sinue Cruz Felix

The predictive synthesis of graded-index (GRIN) optical materials via physical vapor deposition (PVD) is challenged by the non-linear coupling between multi-source flux dynamics and curved substrate geometries. This work introduces a computational framework for the inverse design of source-specific shadow masks in an electron-beam PVD system, moving beyond traditional empirical approaches. Our methodology solves an ill-posed inverse problem to yield prescribed two-dimensional composition profiles on complex aspheric substrates. The forward engine integrates the Knudsen emission law, high-resolution rotation kinematics, and a stochastic penumbra model. A hybrid Particle Swarm Optimization (PSO) and Nelder-Mead algorithm minimizes a multi-objective cost function targeting specific thickness and stoichiometric gradients. Applied to a MgF2/TiO2 co-deposition system on a 24 cm diameter aspheric substrate, the decoupled masks achieve an 88.0% improvement in simulated thickness uniformity over natural deposition, yielding a global RMSE of 4.175 nm. Furthermore, the framework produces a GRIN profile with an index RMSE of 0.1417 relative to the physically attainable target. To establish the reliability of these predictions, a rigorous uncertainty quantification is conducted; a 10,000-iteration bootstrap resampling establishes a 95% confidence interval for the expected RMSE at [5.283, 6.163] nm, suggesting significant stability under manufacturing perturbations. This statistically grounded framework provides a generalizable theoretical pathway for the rational design of high-performance GRIN nanostructures, serving as a predictive roadmap for future experimental validation in vacuum systems.

The coherence of light is essential for understanding interference phenomena, which are pivotal in a wide range of applications. However, due to the technical challenges of conventional methods, quantifying coherence is difficult to achieve in undergraduate optics laboratories. In this work, we present a modification of a method and experimental setup that can enhance the understanding of coherence concepts employing a sensor based on the non-steady-state photo-electromotive force (p-emf) effect. This p-emf sensor generates an electrical current proportional to the square of the interference pattern’s visibility, eliminating the need for image processing and high-quality optical elements, and allowing for real-time measurements. We demonstrated the method by measuring the coherence length of a He-Ne laser and the corresponding length associated with the beat frequency of the laser cavity’s longitudinal modes. This approach is robust, straightforward and simple, making it suitable for implementation in undergraduate optics laboratories.

The rapid and accurate detection of bacteria is essential in medicine, the food industry, and environmental monitoring. This study presents the development of an optic sensor based on color changes in the culture medium, leveraging the optical interaction of bacterial metabolic products. The proposed prototype operates on the principle of optical transmittance through mannitol salt agar (MSA), a selective medium for Staphylococcus aureus. As bacterial growth progresses, the medium undergoes a visible color change, which is optically measurable at specific wavelengths. The sensor demonstrated the ability to detect bacterial growth within approximately 120 minutes, offering a significant reduction in detection time compared to traditional incubation methods. The system is characterized by its simplicity, sensitivity, low reagent consumption, and potential for real-time monitoring. These findings support the feasibility of the proposed sensor as an efficient alternative for early pathogen detection in both clinical and industrial contexts.

In this work, we describe two alternative methods for solving the ill-conditioned inverse problem that allows estimating the particle size distribution (PSD) from turbidimetry measurements. The first method uses the inverse Penrose matrix to solve the inverse problem in its discrete form. The second method consists of replacing an ill-posed problem with a collection of well-posed problems, penalizing the norm of the solution, and it is known as the Tikhonov regularization. Both methods are used to solve a synthetic application of the inverse problem by solving the direct problem using a theoretical expression of the distribution of particles sizes function f(D) and considering soft industrial latex particles (NBR), with average particle diameters of: 80.4, 82.8, 83.6, and 84.5 nm; and three illumination wavelengths in the UV-Vis region: 300, 450, and 600 nm. The estimated solution obtained by the inverse Penrose matrix is different from the original solution due to the inverse problem is ill-conditioned. In contrast, when using Tikhonov’s regularization, the estimate obtained is close to the original solution, which proves that the particle size distribution is adequate. En este trabajo se describen dos métodos alternativos para resolver el problema inverso mal condicionado que permite estimar la distribución de tamaños de partícula (PSD), a partir de mediciones de turbidimetría. El primer método utiliza la matriz pseudo inversa de Penrose para resolver el problema inverso en su forma discreta. El segundo método se conoce como regularización de Tikhonov y consiste en reemplazar un problema mal planteado por una colección de problemas bien planteados, penalizando la norma de la solución. Los dos métodos se usan para resolver una aplicación sintética del problema inverso, la cual se construye resolviendo el problema directo en el que se utiliza una expresión teórica para la distribución de tamaños de partícula y considerando partículas de látex industriales blandos NBR con diámetros promedio de partícula: 80.4 nm, 83.6 nm, 84.5 nm; y tres longitudes de onda en el espectro UV-Vis: 300 nm, 450 nm, 600 nm. Se encuentra que la estimación a la solución que se obtiene usando la matriz de Penrose es muy diferente a la solución original, esto se debe a que el problema es mal condicionado. Por el contrario, al usar la regularización de Tikhonov la estimación encontrada es muy cercana a la solución original lo que comprueba que la distribución de tamaños de partícula es la adecuada.

In this research, we present a prototype optical system that offers significant advances in detecting hydrochloric acid (HCl) and ammonia (NH3) vapors. The system utilizes a natural pigment sensor based on Curcuma longa that is securely attached to a glass surface support. Through extensive development and testing with HCl (37% aqueous solution) and NH₃ (29% aqueous solution) solutions, we have successfully demonstrated the effectiveness of our sensor. To facilitate the detection process, we have developed an injection system that exposes C. longa pigment films to the targeted vapors. The interaction between the vapors and the pigment films triggers a distinct color change, which is then analyzed by the detection system. By capturing the transmission spectra of the pigment film, our system allows a precise comparison of these spectra at different concentrations of the vapors. Our proposed sensor exhibits remarkable sensitivity, allowing the detection of HCl at a concentration of 0.009 ppm using only 100 µL (2.3 mg) of pigment film. In addition, it can detect NH₃ at a concentration of 0.03 ppm with a 400 µL (9.2 mg) pigment film. Integrating C. longa as a natural pigment sensor in an optical system opens up new possibilities for detecting hazardous gases. The simplicity and efficiency of our system, combined with its sensitivity, make it an attractive tool in environmental monitoring and industrial safety applications.

In this paper, the amplitude and phase characteristics of internal reflection of gold nanofilms are investigated using polarization modulation of electromagnetic radiation in the Kretschmann geometry, an excited wavelength of the SPR at 633 nm is considered. The numerical results that are presented in this work are based on the substrate, the variation of the thickness of the dielectric and the type of plasmonic material using gold (Ag), through the ellipsometry parameters Ψ and ∆.

A polymer that has been used for the development of optical components and has had a significant impact is polydimethylsiloxane (PDMS) due to its remarkable mechanical and optical properties and easy handling. We present a practical and straightforward technique for designing and manufacturing a tunable graded index, graphical input (GRIN)-type lenses, and tunable lenses with a homogeneous refractive index made of PDMS. Implementing a biconical surface profile in a tunable plane-convex lens is proposed for elaborating both a homogeneous refractive index lens and a multilayered GRIN-type lens with a constant increased variation of 0.014 on its refractive index. Likewise, we introduce a mechanical mounting system that aims to modify their curvatures and therefore their focal lengths through mechanical stimuli applied on the lenses. Simulations of the optomechanical behavior and optical characterization of the lenses are also presented.