Author

# Gabriel Mellado-Villaseñor

Bio: Gabriel Mellado-Villaseñor is an academic researcher from National Institute of Astrophysics, Optics and Electronics. The author has contributed to research in topics: Phase (waves) & Beam (structure). The author has an hindex of 4, co-authored 12 publications receiving 54 citations.

##### Papers

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TL;DR: It is proved that the diffractive element that generates the vortex with maximum peak intensity has the phase modulation of a propagation-invariant qth order Bessel beam.

Abstract: An annular vortex of arbitrary integer topological charge q can be obtained at the Fourier domain of appropriate phase diffractive optical elements. In this context we prove that the diffractive element that generates the vortex with maximum peak intensity has the phase modulation of a propagation-invariant qth order Bessel beam. We discuss additional advantages of this phase element as annular vortex generator.

27 citations

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TL;DR: It is obtained that the self-healing reaches a limit degree at the far field propagation domain, and that certain relatively small phase obstructions may produce a total damage on the beam.

Abstract: To analyze the self-healing of a partially obstructed optical beam, we represent it by two orthogonal field components. The first component is an exact copy of the unobstructed beam, attenuated by a factor that is computed by a simple formula. The second component represents a pure distortion field, due to its orthogonality respect to the first one. This approach provides a natural measure of the beam damage, due to the obstruction, and the degree of self-healing, during propagation of the obstructed beam. As interesting results, derived in our approach, we obtain that the self-healing reaches a limit degree at the far field propagation domain, and that certain relatively small phase obstructions may produce a total damage on the beam. The theory is illustrated considering a Gaussian beam, distorted by different amplitude and phase obstructions. In the case of a soft Gaussian obstruction we obtain simple formulas for the far field limit values of the beam damage and the self-healing degree.

11 citations

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TL;DR: This study discusses the generation of Hermite- Gauss and Ince-Gauss beams employing phase elements whose transmittances coincide with the phase modulations of such beams, and evaluates such distortion employing the root mean square deviation as a figure of merit.

Abstract: We discuss the generation of Hermite-Gauss and Ince-Gauss beams employing phase elements whose transmittances coincide with the phase modulations of such beams. A scaled version of the desired field appears, distorted by marginal optical noise, at the element's Fourier domain. The motivation to perform this study is that, in the context of the proposed approach, the desired beams are generated with the maximum possible efficiency. A disadvantage of the method is the distortion of the desired beams by the influence of several nondesired beam modes generated by the phase elements. We evaluate such distortion employing the root mean square deviation as a figure of merit.

7 citations

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TL;DR: In this article, numerically and experimentally, the self-healing effect in scaled propagation invariant beams, subject to opaque obstructions, was analyzed and demonstrated, and the effect was quantitatively evaluated employing the Root Mean Square deviation and the similarity function.

Abstract: We analyze and demonstrate, numerically and experimentally, the self-healing effect in scaled propagation invariant beams, subject to opaque obstructions. The effect is quantitatively evaluated employing the Root Mean Square deviation and the similarity function.

6 citations

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TL;DR: A class of synthetic phase holograms (SPHs) applied to the generation of vector fields that encodes the transverse components of the vector field, modulated by different linear phase carriers, are discussed.

Abstract: We discuss a class of synthetic phase holograms (SPHs) applied to the generation of vector fields. Each SPH encodes the transverse components of the vector field, modulated by different linear phase carriers. Such components, which are spatially separated by the carriers, are modulated by appropriate orthogonal polarizations. A final stage that makes the components collinear allows the generation of the vector field. We assess the efficiency and accuracy of the different SPHs, in the task of generating vector fields. The proposal is illustrated by the implementation of vector Bessel beams, which are experimentally generated in a setup based on a phase spatial light modulator.

6 citations

##### Cited by

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Hunan University

^{1}TL;DR: In this article, a vector vortex beam can be decomposed into a vector beam and a vortex, whereby the generation can be realized by sequentially using a q-plate and a spiral phase plate.

Abstract: We propose theoretically and verify experimentally a method of combining a q-plate and a spiral phase plate to generate arbitrary vector vortex beams on a hybrid-order Poincare sphere. We demonstrate that a vector vortex beam can be decomposed into a vector beam and a vortex, whereby the generation can be realized by sequentially using a q-plate and a spiral phase plate. The generated vector beam, vortex, and vector vortex beam are verified and show good agreement with the prediction. Another advantage that should be pointed out is that the spiral phase plate and q-plate are both fabricated on silica substrates, suggesting the potential possibility to integrate the two structures on a single plate. Based on a compact method of transmissive-type transformation, our scheme may have potential applications in future integrated optical devices.

161 citations

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TL;DR: This work approximately generates perfect VVBs with locally linear and elliptical polarizations, and demonstrates that such beams can keep their intensity profile and SoP at a certain propagation distance.

Abstract: We propose the concept of perfect vectorial vortex beams (VVBs), which not merely have intensity profile independent of the polarization order and the topological charge of spiral phase, but also have stable intensity profile and state of polarization (SoP) upon propagation. Utilizing a Sagnac interferometer, we approximately generate perfect VVBs with locally linear and elliptical polarizations, and demonstrate that such beams can keep their intensity profile and SoP at a certain propagation distance. These proposed VVBs can be expanded to encode information and quantum cryptography, as well as to enrich the conversion of spin and orbital angular momenta.

141 citations

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Hunan University

^{1}TL;DR: In this article, a planar Pancharatnam-berry (PB) phase element was proposed to replace all the elements required to obtain the perfect vortex beam for integrated optical communication and micromanipulation systems.

Abstract: Perfect vortex beams are the orbital angular momentum (OAM)-carrying beams with fixed annular intensities, which provide a better source of OAM than traditional Laguerre-Gaussian beams. However, ordinary schemes to obtain the perfect vortex beams are usually bulky and unstable. We demonstrate here a novel generation scheme by designing planar Pancharatnam-Berry (PB) phase elements to replace all the elements required. Different from the conventional approaches based on reflective or refractive elements, PB phase elements can dramatically reduce the occupying volume of system. Moreover, the PB phase element scheme is easily developed to produce the perfect vector beams. Therefore, our scheme may provide prominent vortex and vector sources for integrated optical communication and micromanipulation systems.

112 citations

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TL;DR: A simple method to generate a configurable annular vortex beam (AVB) with the maximum possible peak intensity, employing a phase hologram whose transmittance is the phase of a Bessel beam.

Abstract: We discuss a simple method to generate a configurable annular vortex beam (AVB) with the maximum possible peak intensity, employing a phase hologram whose transmittance is the phase of a Bessel beam. Due to its maximum intensity, the AVB provides the optimal density of the orbital angular moment. Another attribute of the generated AVB is the relatively high invariance of the intensity profile when the topological charge is changed. We demonstrate the advantages and flexibility of these AVBs for optical trapping applications.

78 citations

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TL;DR: In this paper, the authors demonstrate optical trapping and manipulation of microparticles suspended in water due to laser-induced convection currents, which are generated by laser light absorption in an hydrogenated amorphous silicon (a:Si-H) thin film.

Abstract: In this work we demonstrate optical trapping and manipulation of microparticles suspended in water due to laser-induced convection currents. Convection currents are generated due to laser light absorption in an hydrogenated amorphous silicon (a:Si-H) thin film. The particles are dragged towards the beam's center by the convection currents (Stokes drag force) allowing trapping with powers as low as 0.8 mW. However, for powers >3 mW trapped particles form a ring around the beam due to two competing forces: Stokes drag and thermo-photophoretic forces. Additionally, we show that dynamic beam shaping can be used to trap and manipulate multiple particles by photophotophoresis without the need of lithographically created resistive heaters.

68 citations