Person: Sánchez Brea, Luis Miguel
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First Name
Luis Miguel
Last Name
Sánchez Brea
Affiliation
Universidad Complutense de Madrid
Faculty / Institute
Ciencias Físicas
Department
Óptica
Area
Optica
Identifiers
16 results
Search Results
Now showing 1 - 10 of 16
Item Near field diffraction of steel tape gratings illuminated with finite-size incoherent sources(Optik, 2022) Torcal Milla, Francisco José; Sánchez Brea, Luis MiguelSteel tape gratings are diffraction gratings engraved on a steel substrate, whose slits are commonly manufactured by laser ablation. They behave as amplitude diffraction gratings, since the engraved slits act as strong scatters. Here, we extend previous works to the case of finite-size illumination sources, as they are used in applications such as optical encoders, where LEDs are commonly used as illumination sources. We obtain an analytical formulation for the near field behavior of this kind of gratings. When the light source increases its size, a decreasing in the contrast of the self-images is added to the effect of the surficial roughness. The agreement between analytical and numerical results is high, validating the obtained formulation. Besides, these results could be crucial in metrological applications in which steel tape gratings or other diffractive optical elements engraved on steel substrates are used, providing with a theoretical formalism to analyze the near field propagation of light after reflecting in them.Item Gold-coated split laser-induced periodic surface structures as refractometric sensors(Optics and Laser Technology, 2022) San Blas, Alejandro; Elshorbagy, Mahmoud Hamdy Mohamed; Olaizola Izquierdo, Santiago M.; Sánchez Brea, Luis Miguel; Rodríguez González, Ainara; Del Hoyo Muñoz, Jesús; Granados, Eduardo; Soria García, Ángela; Pastor Villarrubia, Verónica; Alda Serrano, JavierThe generation of surface plasmon resonances (SPR) in laser-induced periodic surface structures (LIPSS) allows their application in the field of optical sensing, such as the detection of refractive index variations in gases and liquids. We have fabricated gold-coated LIPSS nanostructures on stainless steel substrates by using femtosecond laser nano-ablation. This technique is a low-cost and high-throughput fabrication method applicable to fast and large-scale manufacturing. The depth profile of the fabricated LIPSS shows a central dip at the top of each ripple that split the geometry. The actual topography is modeled and included in a computational electromagnetism package to obtain the expected optical response under the experimental conditions. The measured and simulated spectral reflectances are compared, and the differences are explained by the departure of the fabricated LIPSS from the ideal topography. The experiments and simulations showed excellent agreement for the main spectral characteristics, like the Fano-like lineshapes of the spectral reflectance. This fitting provides the values used to determine the refractometric performance of the fabricated device, that shows a sensitivity of 518 nm/RIU and a figure of merit of 32 RIU−1 for an aqueous analyte. Our experimental results show that the fabricated devices are competitive in terms of cost and simplicity when compared to existing devices with similar performance.Item High precision calibration method for a four-axis Mueller matrix polarimeter(Optics and lasers in engineering, 2020) Hoyo Muñoz, Jesús del; Sánchez Brea, Luis Miguel; Gómez Pedrero, José AntonioWe present a novel method for calibrating a four-axis Mueller matrix polarimeter. This method is valid even for non-ideal optical elements, as it models all polarization elements having both diattenuation and retardance. The method is divided in seven experimental steps, where all the optical elements are calibrated each at a time, plus a numerical fitting process. The fitting method is flexible, allowing to choose between accuracy and speed. The error obtained after the fitting is lower than 0.5% for all steps, and the final error in the determined Mueller matrix elements can be reduced to 4 ×10 −4.Item Stokes polarimeter using vector diffractive optical elements(2023) Soria García, Ángela; Del Hoyo Muñoz, Jesús; Sánchez Brea, Luis Miguel; Pastor Villarrubia, Verónica; González Fernández, Verónica; Elshorbagy, Mahmoud H.; Alda Serrano, JavierWe designed, fabricated and tested a Vector Diffractive Optical Element (VDOE) to simultaneously determine the Stokes vector of light. It comprises several sectors. Each one is a vector Fresnel zone plate which focuses the light on separate foci and has different polarization properties. The polarization state is calculated from their intensities. From simulations, we could identify the error sources that were analytically removed. The residual uncertainty after applying our corrections was as low as 6x10^(-5). The uncertainty obtained for our fabricated VDOE, 3.33 %, is competitive with the results from state-of-the-art techniques.Item Fabrication effects in the optical performance of DOEs engraved with femtosecond lasers(Proceedings of SPIE, 2021) Soria García, Ángela; Fantova, Jorge; San Blas, Alejandro; Hoyo Muñoz, Jesús del; Sánchez Brea, Luis Miguel; Alda Serrano, Javier; Rodríguez González, Ainara; Olaizola Izquierdo, Santiago M.The development of DOEs fabrication techniques is continuously growing due to the wide range of industrial applications, such as beam manipulation or optical position encoders. In this work, we use Femtosecond laser direct writing to manufacture DOEs, which uses a simpler and more efficient way to fabricate amplitude binary masks. Also, we have analyzed the performance of the DOEs. The fabrication technique is validated since the experimental results are in accordance to numerical simulations.Item Calibration method to determine the complete Jones matrix of SLMs(Optics and Lassers in Engineering, 2021) Hoyo Muñoz, Jesús del; Sánchez Brea, Luis Miguel; Soria García, ÁngelaWe present a simple method to determine the polarimetric properties of spatial light modulators (SLMs) for each grey level by means of irradiance measurements. The Jones matrix of the SLM is obtained without any assumption about its properties, so it can be applied for more devices than previous works. This method is simple enough to be quickly performed, while offers better results than previous works, as it reduces the error in the prediction of transmission intensities in a factor between 5 and 380.Item Permeable Diffractive Optical Elements for the real-time sensing of running fluids(2023) Pastor Villarrubia, Verónica; Soria García, Ángela; Del Hoyo Muñoz, Jesús; Sánchez Brea, Luis Miguel; Alda Serrano, JavierThe real-time monitoring of physical and chemical parameters in running fluids is of importance for biomedical, biochemical, and environmental applications, such as the presence of biomarkers or chemomarkers, or the departure from some preset values of critical parameters. In this contribution we present a new generation of Permeable Diffractive Optical Elements (PDOE) based on photon sieves. In brief, the PDOE is made of passing holes properly placed on specific locations on a rigid surface. This arrangement makes PDOEs ideal to work with running fluids. Our PDOE is optimized maximizing the irradiance at is focal plane, maintaining an appropriate permeability ratio. The starting point is the classical Fresnel zone distribution. We have used two different optimization strategies to design a working PDOE: i) Particle Swarm Optimization has been applied to modify the distribution of holes on the PDOE simultaneously considering all of them; ii) an iterative minimization algorithm adding one hole at the time until filling the PDOE aperture. Both optimization algorithms generate focal spots that are compared to choose the design better suited for the proposed application. Once the PDOE is optimized and fabricated, the surface of the remaining rigid structure is nanostructured (for example using Laser Induced Periodic Surface Structures), or functionalized, to provide specific sensing capabilities. In addition, the PDOE is integrated within a pipe where the fluid under analysis circulates through. A proposal for the optoelectronic assembly of the device-including auxiliary optical elements, light sources, and detectors - is also presented in this contribution.Item Design and numerical analysis of metallic Ronchi diffraction gratings acting as reflective beam-splitter(Optik- international journal for light and electron optics, 2022) Torcal Milla, Francisco José; Sánchez Brea, Luis MiguelIn this work, a reflective beam-splitter based on a metallic Ronchi diffraction grating normally illuminated is designed and analysed. This kind of beam-splitter could have potential applications in photonics and optical technologies in which robustness is necessary since it may be manufactured over malleable metallic substrates.Methods: The main idea under the design is as simple as obligating the zero-th diffraction order to be null. Firstly, scalar approach is performed, showing an approximation to the parameters of the grating necessary to cancel zero-th diffraction order. After that, a more rigorous approach such as Rigorous Coupled Waves Analysis (TE and TM polarization) is used to evaluate the proposed diffraction gratings as reflective beam-splitters.Results: Beam-splitting is demonstrated for TE and TM polarization with slightly different dimensional parameters of the diffraction grating. Besides, we show how physical height of the grating grooves that allows cancelling zero-th diffraction order for a certain illumination wave-length depends on the metals used to manufacture the grating and its period. The dependence of the grooves height on the period is exponentially decreasing. To complete the analysis, we demonstrate how for a given grating period, the grooves height also depends on the illumination wavelength.Item Diffraction Efficiency of Reflective Metallic Gratings Operating in the THz Range(IEEE Transactions on Terahertz Science and Technology, 2023) Cuadrado Conde, Alexander; Fernández Rodríguez, M; Sánchez Brea, Luis Miguel; García Lozano, Gonzalo; Mercant, Guillermo; Torquemada ,Mº Carmen; Alda Serrano, Javier; Gonzalez , Luis M.; Belenguer Dávila, TomásFar infrared spectrometers have a prominent role to play in future space missions devoted to unveiling the obscure universe. Diffraction gratings are the heart of these instruments that, when operating in the range of a few THz, shall cover a wide spectral range providing the highest resolution and efficiency, generally for only a single polarization, within the specified spectral range. This contribution describes the optimization of the diffraction efficiency of the first diffractive order for a blazed metallic grating working at a large angle of incidence. Since the grating period is of the same order of magnitude as the wavelength, it is necessary to approach the design by solving Maxwell's equations rigorously using computational electromagnetism. We have applied the Rigorous Coupled-Wave Analysis and the Finite Element Methods to simulate the performance of the grating. This analysis provides relevant hints for the selection of the period, and the blaze and slant angles of the grating. A metallic blazed grating has been fabricated on aluminum and its topography has been characterized to determine the discrepancies with respect to the nominal values. The fabricated profile has been simulated to obtain the expected results in efficiency in comparison with the ideal case. This analysis provides guidance for improved manufacturing processes and experimental verification.Item Fourier series diffractive lens with extended depth of focus(Optics and laser technology, 2023) Soria García, Ángela; Sánchez Brea, Luis Miguel; Hoyo Muñoz, Jesús, del; Torcal Milla, Francisco José; Gómez Pedrero, José AntonioAngular diffractive lenses have been proven to achieve a narrow beam waist with a long depth of focus. We generalize these type of lenses by defining the angular distribution of the focal length as a Fourier series. The Fourier coefficients of the lens are optimized, using Particle Swarm Optimization algorithm, to minimize the beam width and increase its uniformity for a given depth of focus. In order to obtain a fast simulation during the optimization process, we used Chirp Z-transform algorithm. Finally, we performed an experimental verification of the results using a Spatial Light Modulator. The Fourier series diffractive lens presents a more uniform and narrower beam than previous angular lenses, in both simulations and experiments. These results may find applications in the design of contact and intraocular lenses with extended depth of focus, laser focusing and imaging systems.