Research — Carlos Chacón

Research Areas

Three Lines of Work

Current PhD Research

Tomographic Diffractive Microscopy

Quantitative 3D optical imaging based on holography, angular illumination, and Fourier-space reconstruction of the refractive-index distribution.

Miniaturized Scintillator Dosimetry

Compact optical-fiber-based radiation detectors for high-resolution dose verification in small and localized radiation therapy fields.

Electron Microscopy & Multi-Scale Imaging

SEM, EDS, and multi-scale imaging workflows for materials characterization, mineral identification, and porous media analysis.

Tomographic Diffractive Microscopy

Recovering the three-dimensional refractive-index distribution of microscopic samples from holographic measurements acquired at multiple illumination angles.

Tomographic Diffractive Microscopy is a quantitative optical imaging technique that reconstructs the internal structure of transparent or weakly scattering samples. Instead of recording only a conventional microscope image, the system measures holograms under multiple illumination angles. Each illumination direction captures a different portion of the sample information in Fourier space.

By combining these measurements, it becomes possible to reconstruct a three-dimensional map of the sample, including variations in refractive index and absorption — without fluorescent labels or sample staining.

Current focus: development of a dual-opposite-view tomographic configuration inspired by 4π microscopy. By combining two opposed transmission views, this approach aims to reduce depth-dependent degradation in the reconstructed volume and partially recover the axial information that is poorly sampled in conventional single-view tomographic microscopy.

Reconstruction pipeline

1Hologram
acquisition

→

2Fourier
filtering

→

3Phase
retrieval

→

4Ewald
mapping

→

53D
reconstruction

▸ Technical focus

The reconstruction pipeline relies on off-axis interferometry, complex-field retrieval, phase unwrapping, aberration correction, Rytov/Born-based scattering models, and numerical mapping of the measured fields onto Ewald surfaces in 3D Fourier space.

TDM setup — optical path

Raw holographic measurement

Hologram acquisition

Fourier-space filtering

Extraction of diffracted order

Ewald sphere mapping

Angular information in reciprocal space

3D refractive-index volume

Recovered volume

Radiation Detection

Miniaturized Scintillator Dosimetry

Compact optical sensors for measuring radiation dose in highly localized therapeutic beams.

Modern radiation therapy increasingly uses small and highly focused radiation fields. These fields can deliver dose with strong spatial gradients, which makes accurate dosimetry challenging. Conventional detectors may suffer from volume-averaging effects or may perturb the radiation field they are intended to measure.

Miniaturized scintillator dosimeters provide an optical solution to this problem. A small scintillating element converts ionizing radiation into light, which is then guided through an optical fiber toward a detector. Because of their compact geometry, these sensors can probe small radiation fields with high spatial resolution.

This research explored the use of a miniaturized inorganic scintillator detector coupled to a narrow optical fiber through a photonic interface. The detector was evaluated under medical photon beams and compared with high-resolution reference probes — including micro-diamond detectors and silicon diodes.

Small sensitive volume

Reduces volume averaging in steep dose gradients.

Optical fiber readout

Light from the scintillator transported through a narrow silica fiber.

Dose verification

Validates delivered dose in small-field radiation therapy.

Reference comparison

Benchmarked against micro-diamond and silicon diode detectors.

Related work: Miniaturized scintillator dosimeter for small field radiation therapy, Physics in Medicine & Biology, 2021.

Miniaturized scintillator dosimeter — detector scheme

Scintillator detector · Beam → fiber → photodetector

Dose profile comparison

Measured vs. reference dose profiles

2D dose map — small photon field

2D dose distribution

Electron Microscopy

Electron Microscopy & Multi-Scale Imaging

Connecting structure, composition, and texture from the millimetre scale down to the micro- and nanoscale using SEM, EDS, and integrated workflows.

Electron microscopy provides a bridge between morphology and composition. Secondary-electron imaging reveals surface topography, backscattered-electron imaging highlights compositional contrast, and energy-dispersive X-ray spectroscopy identifies the elemental distribution of the sample.

This research area focuses on the interpretation of geological and material samples using SEM, EDS, and multi-scale imaging workflows — correlating structural information, mineralogy, porosity, and texture across different spatial scales.

Multi-Scale Imaging for Unconventional Reservoirs

Multi-scale imaging workflows combine X-ray micro-computed tomography, SEM, EDS, QEMSCAN, and image analysis to study complex porous materials such as shales, tight sandstones, and carbonates. The integration of these datasets supports digital rock physics and helps evaluate porosity, pore connectivity, pore-size distribution, and permeability-related features.

SEM Training & Scientific Imaging

In addition to research applications, this line of work includes training activities in scanning electron microscopy. The training focuses on image acquisition, contrast mechanisms, sample preparation, EDS analysis, mineral identification, and interpretation of microstructural features.

▸ Technical note — EDS interpretation

EDS interpretation requires careful control of accelerating voltage, detector geometry, take-off angle, count rate, dead time, peak overlap, absorption effects, and matrix corrections such as ZAF or Phi-Rho-Z methods.

Scanning electron microscopy — multi-scale imaging

SEM · multi-scale imaging workflow

Keywords

Research Interests

My work connects optical physics, numerical reconstruction, radiation detection, and materials characterization.

Tomographic Diffractive Microscopy Off-Axis Holography Fourier Optics 3D Reconstruction Ewald Sphere Mapping Optical Transfer Function Inverse Problems Scientific Computing Radiation Detection Scintillator Dosimetry Small-Field Radiotherapy Scanning Electron Microscopy EDS / EDX Microanalysis Multi-Scale Imaging Digital Rock Physics Materials Characterization Phase-Contrast Microscopy Data Visualization

Publications

Selected Work

Radiation dosimetry · Medical physics

Miniaturized scintillator dosimeter for small-field radiation therapy

Development and evaluation of a compact inorganic scintillator detector coupled to an optical fiber for high-resolution dose measurements in small photon fields.

View publication →

Multi-scale imaging · Digital rock physics

A Generalized Workflow for the Integral Evaluation of Unconventional Reservoirs Using Multi-Scale Imaging and Analyses

A workflow integrating micro-CT, SEM, QEMSCAN, and image analysis to evaluate mineralogy, pore structure, and petrophysical properties in unconventional reservoir samples.

View publication →

PhD research · Optical microscopy

Current PhD Research — Tomographic Diffractive Microscopy

Ongoing development of a dual-opposite-view tomographic diffractive microscopy configuration for improved 3D optical reconstruction beyond the single-view limit.

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View full publication list on Google Scholar →

Get in touch

Interested in collaboration?

I am open to research collaborations involving quantitative microscopy, optical imaging, electron microscopy, radiation detection, scientific visualization, and computational reconstruction.

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