Medida del coeficiente de absorción de medios materiales no colaborativos

Speaker: Juan Carlos Martínez-Antón

Date: 2026/june/24

Place: Faculty of Physics

Es de sobra conocido la importancia de la espectroscopía de absorción óptica para todo tipo de propósitos: física y propiedades de medios materiales, análisis químicos e identificación de sustancias, control de calidad en farmacia, agroalimentario, en contaminación medioambiental, etc…. El propósito de esta charla es dar cuenta de las bases ópticas habituales para hacer una espectroscopía cuantitativa fiable y ver las limitaciones que nos encontramos al abordar formatos materiales “no colaborativos”, por ejemplo, en medios con scattering, en granulados y polvos, espumas, fibras, etc. En este seminario veremos que al iluminar las muestras de forma uniforme e inmersiva (mediante una esfera integradora) podemos simplificar mucho el modelo óptico de interacción y con ello la ligadura con el coeficiente de absorción α(λ) propiedad intrínseca del material. Veremos de forma analítica y experimental cómo podemos medir α(λ) de manera fiable y en casi cualquier formato material con tal de que la muestra cumpla unos requisitos fácilmente abordables. Cómo resultado añadido descubriremos que cualquier objeto no absorbente es invisible bajo el tipo de iluminación indicada.

Polarizer-free single-molecule orientation and localization microscopy via Fourier light field microscopy

Speaker: Arturo García Vesga

Date: 2026/june/24

Place: Faculty of Physics

Single-molecule orientation and localization microscopy (SMOLM) enables simultaneous determination of molecular position, orientation, and rotational dynamics. However, most SMOLM implementations rely on computationally intensive point spread function (PSF) fitting, which limits throughput and scalability. Here, we introduce a polarization-free, ratiometric framework for three-dimensional SMOLM based on Fourier light field microscopy. By leveraging a generalized three-dimensional Stokes formalism, intensity measurements across light-field channels are linearly decomposed, enabling computationally efficient estimation without PSF fitting or polarization optics. This approach, termed SMOLM-LFM, enables six-dimensional single-molecule characterization (3D position and 3D orientation) with a simplified optical architecture and an extended depth of field. We present the theoretical framework, experimental implementation, and validation using calibration beads, single fluorophores, and cellular samples. We demonstrate the capability of SMOLM-LFM to probe dynamic processes by quantifying molecular mobility in lipid membranes. By jointly tracking translational motion and orientation fluctuations, our method provides access to rotational freedom within homogeneous and heterogeneous membrane environments, offering new insight into nanoscale membrane organization and dynamics. These results establish SMOLM-LFM as a versatile and computationally efficient platform for high-dimensional single-molecule imaging, bridging structural and dynamical measurements in complex biological systems.

Recent Advances in Polarimetry at the AOCG

Speaker: Jesús del Hoyo

Date: 2026/jan/16

Place: Faculty of Physics

Abstract: Over the past eight years, we have participated in several research projects related to polarimetry. In this seminar, we present the main milestones achieved in this field of optics. First, the capabilities of the open-source software module py_pol will be introduced. Next, results in Mueller polarimetry will be presented, including the development of a high-precision Mueller polarimeter. Finally, recent advances in the characterization of polarizers and retarders for high-precision polarimetry will be discussed.

Links: Presentation,  video

Metrics for comparison of image datasets and segmentation methods for fractal analysis of retinal vasculature

Speaker: Asmae Igalla (Universidad Complutense de Madrid)

Date: 2025/april/05

Place: Faculty of Optics and Optometry

Abstract: Fractal analysis of retinal vasculature is a key tool for characterizing pathologies and studying healthy retinas. Its accuracy depends on factors such as the fractal method employed, segmentation and image quality. In this talk I will present some metrics that we have developed to evaluate the influence of these factors, allowing us to quantify differences between methods and improve the criteria for their use in retinal diagnosis and characterization.