Sánchez Brea, Luis Miguel

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First Name
Luis Miguel
Last Name
Sánchez Brea
Universidad Complutense de Madrid
Faculty / Institute
Ciencias Físicas
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Search Results

Now showing 1 - 10 of 12
  • Publication
    Far field of binary phase gratings with errors in the height of the strips
    (SPIE, 2009-06-17) Rico-García, José María; Sánchez Brea, Luis Miguel
    Diffraction gratings are not always ideal but, due to the fabrication process, several errors can be produced. In this work we show that when the strips of a binary phase diffraction grating present certain randomness in their height, the intensity of the diffraction orders varies with respect to that obtained with a perfect grating. To show this, we perform an analysis of the mutual coherence function and then, the intensity distribution at the far field is obtained. In addition to the far field diffraction orders, a "halo" that surrounds the diffraction order is found, which is due to the randomness of the strips height.
  • Publication
    Fabrication effects in the optical performance of DOEs engraved with femtosecond lasers
    (SPIE, 2021-09-17) 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.
  • Publication
    Diffractive performance of square Fresnel zone plates
    (Elsevier, 2009-06-14) Alda, Javier; Rico García, José María; Salgado Remacha, Francisco Javier; Sánchez Brea, Luis Miguel
    We analyze the optical behavior of square Fresnel zones plates. A theoretical analysis and numerical simulations based on the Rayleigh-Sommerfeld approach have been developed analyzing properties such as the depth of focus and the intensity of the focus in terms of the number of zones. In addition, an experimental verification has been performed using a Spatial Light Modulator to implement the designed square Fresnel zones plates.
  • Publication
    Diffractive optical elements with square concentric rings of equal width
    (John Wiley & Sons INC, 2010-04) Alda, Javier; Sánchez Brea, Luis Miguel; Salgado Remacha, Francisco Javier; Rico-García, José María
    A diffractive optical element having equal-width concentric square rings is analyzed in this article. This constant width makes possible its realization using spatial light modulators or square pixels phase screens. It allows a simple analytical treatment, and the element is also simulated using the Rayleigh-Sommerfeld approach. An experimental verification of its performance has been compared with the simulated results.
  • Publication
    Vector diffractive optical element as a full-Stokes analyzer
    (Elsevier, 2023-03-29) Soria García, Ángela; del Hoyo Muñóz, Jesús; Sánchez Brea, Luis Miguel; Pastor Villarubia, Verónica; González Fernández, Verónica; Elshorbagy, Mahmoud Hamdy Mohamed; Alda, Javier
    The real-time characterization of the polarization state of a light beam is of importance for a variety of applications in Optics and Photonics. We have designed a device that includes a Vector Diffractive Optical Element (VDOE) to determine the polarization state of an incident light beam. The device is able to simultaneously evaluate the four Stokes parameters of the light under analysis. The VDOE is sectorized into several Fresnel zone plates, enabling a compact arrangement and facilitating optoelectronical integration. We have also developed a procedure to remove diffractive effects and systematic errors. From the simulated results, our device is able to identify any polarization incident state with an averaged uncertainty of 0.006%. Finally, we have experimentally verified the VDOE with non-ideal polarization elements to further validate and test our proposed design. The averaged uncertainty of our experimental realization is 3.33%.
  • Publication
    Optimal phase distributions for polygonal Fresnel lenses
    (IEEE, 2010) Alda, Javier; Salgado Remacha, Francisco Javier; Sánchez Brea, Luis Miguel; Rico-García, José María; González, Francisco Javier
    Polygonal Fresnel zone plates can be configured in a variety of forms depending on the number of sides of the polygon and the number of phase steps used. This contribution deals with some specific polygonal designs that tessellate the plane: triangles, squares, and hexagons. The phase distribution is chosen as a continuous one to form a polygonal kinoform. The selected designs have been simulated and its behaviour compared. Although their performance is worse than the circular Fresnel plate, they may present some other advantages as the tessellation capability, and the possibility to fabricate them as extruded profiles.
  • Publication
    Fourier series diffractive lens with extended depth of focus
    (Elsevier, 2023-04-11) Soria García, Ángela; Sánchez Brea, Luis Miguel; Hoyo Muñoz, Jesús, del; Torcal Milla, Francisco José; Gómez Pedrero, José Antonio
    Angular 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.
  • Publication
    Optimization of angular diffractive lenses with extended depth of focus
    (IOP Publishing, Ltd., 2020-04-02) Sánchez Brea, Luis Miguel; Torcal Milla, Francisco José; Hoyo Muñoz, Jesús del; Cuadrado Conde, Alexander; Gómez Pedrero, José Antonio
    Conventional refractive lenses concentrate the incident light at focal distance. A narrow beam waist can be achieved by increasing the lens numerical aperture, but strongly reduces the depth of focus. In this paper, we explore diffractive lenses designs, with fast angular variation of the focal distance, that produce both a narrow beam waist and a long depth of focus. We predict the focusing properties or the diffractive lenses with a simple analytical model based on an incoherent superposition of standard lenses with different focal distances. The histogram of the local focal distances is used to determine the weights in the superposition. Our model optimizes the shape of the diffractive lenses, in order to extend the depth of focus, which corresponds to the lotus lens. We verify our results with numerical simulations based on Rayleigh-Sommerfeld approach. Experimentally, we validate our analytical and numerical solutions with a Spatial Light Modulator are carried out and compared to the analytical and numerical results. We have found configurations for the lotus lens where the depth of focus is significantly incremented with only a slight increment of the focal width. For example, we increased the depth of focus from 7.6 mm to 37.2 mm while the beam waist varied from 35.0 microns to 51.6 microns for a lens with diameter D~=~4~mm, and focal distance f'~=~125~mm. These results may find applications in the design of contact and intraocular lenses with extended depth of focus, laser focus generators, and imaging applications where extended depth of focus is needed.
  • Publication
    Optimized square Fresnel zone plates for microoptics applications
    (SPIE, 2009-06-17) Rico-García, José María; Salgado Remacha, Francisco Javier; Sánchez Brea, Luis Miguel; Alda, Javier
    Polygonal Fresnel zone plates with a low number of sides have deserved attention in micro and nanoptics, because they can be straightforwardly integrated in photonic devices, and, at the same time, they represent a balance between the high-focusing performance of a circular zone plate and the easiness of fabrication at micro and nano-scales of polygons. Among them, the most representative family are Square Fresnel Zone Plates (SFZP). In this work, we propose two different customized designs of SFZP for optical wavelengths. Both designs are based on the optimization of a SFZP to perform as close as possible as a usual Fresnel Zone Plate. In the first case, the criterion followed to compute it is the minimization of the difference between the area covered by the angular sector of the zone of the corresponding circular plate and the one covered by the polygon traced on the former. Such a requirement leads to a customized polygon-like Fresnel zone. The simplest one is a square zone with a pattern of phases repeating each five zones. On the other hand, an alternative SFZP can be designed guided by the same criterion but with a new restriction. In this case, the distance between the borders of different zones remains unaltered. A comparison between the two lenses is carried out. The irradiance at focus is computed for both and suitable merit figures are defined to account for the difference between them.
  • Publication
    Binary gratings with random heights
    (OSA Publishing, 2009-06-01) Rico-García, José María; Sánchez Brea, Luis Miguel
    We analyze the far-field intensity distribution of binary phase gratings whose strips present certain randomness in their height. A statistical analysis based on the mutual coherence function is done in the plane just after the grating. Then, the mutual coherence function is propagated to the far field and the intensity distribution is obtained. Generally, the intensity of the diffraction orders decreases in comparison to that of the ideal perfect grating. Several important limit cases, such as low- and high-randomness perturbed gratings, are analyzed. In the high-randomness limit, the phase grating is equivalent to an amplitude grating plus a “halo.” Although these structures are not purely periodic, they behave approximately as a diffraction grating.