Person:
Sánchez Brea, Luis Miguel

First Name

Luis Miguel

Last Name

Sánchez Brea

URI

https://hdl.handle.net/20.500.14352/75070

Affiliation

Universidad Complutense de Madrid

Faculty / Institute

Ciencias Físicas

Department

Óptica

Area

Optica

Identifiers

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Search Results

Now showing 1 - 10 of 10

Optimal phase distributions for polygonal Fresnel lenses
(Proceedings of the Fourth European Conference on Antennas and Propagation, 2010) Alda Serrano, 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.
Rough Fresnel zone plates over metallic surfaces
(Applied Optics, 2010) Salgado Remacha, Francisco Javier; Sánchez Brea, Luis Miguel; Álvarez Ríos, Francisco Javier; Bernabeu Martínez, Eusebio
We analyze the focusing properties of Fresnel zone plates fabricated over steel tapes using laser ablation. Our intention is to implement the use of micro-optical elements when the use of conventional chrome–glass elements is not indicated. Because of the manufacture process, the surface presents a certain anisotropic roughness, which reduces the focusing properties. First, we develop numerical simulations by means of the Rayleigh–Sommerfeld approach, showing how roughness in both levels of the Fresnel zone plate affects the focalization of the lens. We also manufacture Fresnel zone plates over steel tape, and perform experimental verification that corroborates the numerical results.
Effect of fill-factor on the Talbot effect of diffraction gratings
(Journal of the European Optical Society-Rapid Publications, 2011) Salgado Remacha, Francisco Javier; Sánchez Brea, Luis Miguel; Bernabeu Martínez, Eusebio
We analyze the effect of the fill factor of binary diffraction gratings on the near field propagation. We show that the location of the best-visibility planes changes with the configuration parameters of the grating, that is, the amplitude and phase modulation and the fill factor. Moreover, different intensity patterns and contrast shapes can be obtained when different configurations are used. Analytical expressions describing the contrast of the diffracted field are obtained, that agree with numerical simulations.
Micromachining of Diffractive Optical Elements Embedded in Bulk Fused Silica by Nanosecond Pulses
(Journal of Lightwave Technology, 2011) Salgado Remacha, Francisco Javier; Sánchez Brea, Luis Miguel; Bernabeu Martínez, Eusebio
Micro-optical devices embedded in transparent materials are usually manufactured focusing a pulsed laser in bulk fused silica. Under this condition, pulsewidth becomes the most important parameter that rules the size of the inscriptions. Ultrafast pulses (pico- and femtosecond pulses) avoid thermal effects and the results present a high efficiency. Nevertheless, nanosecond lasers are more available due the reduced costs. Therefore, a study of the optical behavior of embedded elements micromachined by nanosecond pulses is required. In this study, we show that this regime of pulses can still be used for engraving diffractive optical elements in transparent materials, regardless of the thermal damage. A Fresnel zone plate and a far-field beam shaper have been manufactured as an example of the functionality of these devices.
Collimation method using a double grating system
(Applied Optics, 2010) Sánchez Brea, Luis Miguel; Torcal Milla, Francisco José; Salgado Remacha, Francisco Javier; Morlanes Calvo, Tomás; Jiménez Castillo, Isidoro; Bernabeu Martínez, Eusebio
We present a collimation technique based on a double grating system to locate with high accuracy an emitter in the focal plane of a lens. Talbot self-images are projected onto the second grating producing moiré interferences. By means of two photodetectors positioned just behind the second grating, it is possible to determine the optimal position of the light source for collimation by measuring the phase shift between the signals over the two photodetectors. We obtain mathematical expressions of the signal in terms of defocus. This allows us to perform an automated technique for collimation. In addition, a simple and accurate visual criterion for collimating a light source using a lens is proposed. Experimental results that corroborate the proposed technique are also presented.
Self-imaging with curved gratings
(Optics Communications, 2010) Torcal Milla, Francisco José; Sánchez Brea, Luis Miguel; Salgado Remacha, Francisco Javier; Bernabeu Martínez, Eusebio
We analyze the near field behavior of binary amplitude gratings which present a curved profile. This configuration has an important application in rotary optical encoders. This kind of encoders is used to measure the angular displacement between two different parts of the devices. To our knowledge, its behavior in the near field has not been analyzed yet. We have found that Talbot effect is produced but the period of the self-images and Talbot distances change as we separate from the grating. We have fabricated a curved grating and have performed the experiment to corroborate the behavior theoretically found. This fact could be useful in systems that use Talbot effect to measure displacements, since the mechanical tolerances grow.
Diffractive optical elements with square concentric rings of equal width
(Microwave and Optical Technology Letters, 2010) Alda Serrano, 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.
Diffractive performance of square Fresnel zone plates
(Optics Communications, 2009) Alda Serrano, 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.
Use of steel substrates in diffractive optics: Near field of high surface quality steel tape gratings
(Optics and Lassers in Engineering, 2011) Salgado Remacha, Francisco Javier; Torcal Milla, Francisco José; Sánchez Brea, Luis Miguel; Bernabeu Martínez, Eusebio
Steel tape is used in optical applications due to its mechanical properties. However, roughness of steel surfaces affects to wave propagation. The effect can be observed using diffraction gratings with low periods. In such a case, self-images of the grating appear at certain periodic distances from the grating (Talbot planes). When standard steel is used, the contrast of Talbot self-images strongly decreases with the distance from the grating. In this work, we prove that controlling the surface quality of steel, it is possible to improve its optical behavior and, as a consequence, high quality surface steel represents a good choice for diffractive optics when the use of chrome-on-glass masks is not indicated. As an example, we have manufactured a diffraction grating over a high quality steel surface by means of an ablation process with a nanosecond pulsed laser. The contrast of the self-images for these gratings decreases very slowly with the distance, in comparison with the self-images obtained with standard steel tape gratings.
Optimized square Fresnel zone plates for microoptics applications
(Modeling Aspects in Optical Metrology II., 2009) Rico García, José María; Salgado Remacha, Francisco Javier; Sánchez Brea, Luis Miguel; Alda Serrano, 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.