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New paper in OLEN analyzing the diffraction efficiency of stepped gratings in large phase modulation SLMs

OLENOur new publication is available in Optics & Lasers in Engineering, entitled Diffraction efficiency of stepped gratings using high phase-modulation spatial light modulators.

We study the diffraction efficiency of linear phase (blazed) diffraction gratings displayed onto SLMs that exhibit a large phase modulation range, reaching a maximum phase modulation of 8pi or 10pi radians. We analyse these effects for their important implications in the Nyquist limit for diffractive elements

The paper has been done in collaboration with our friends at San Diego State University.

Domingo, 3 de noviembre de 2019 Sin comentarios

New paper in OLEN with a technique to generate vector beams

OLENA new publication of our team is available at the journal Optics & Lasers in Engineering, entitled Efficient on-axis engineering of optical vector modes.

In this work we present a method for the efficient experimental generation of arbitrary polarized vector beam modes. The optical system employs two LCOS-SLMs in a common path architecture, avoiding the use of beam-splitters.

We apply a recently proposed random technique to encode complex amplitude values. This encoding technique reconstructs the complex function on-axis, thus avoiding incorporating carrier phases. We demonstrate arbitrary scalar modes encoded onto orthogonal polarization components, whose superposition results in a vector beam mode.

Categories: Publications, Research Tags:

Sábado, 28 de septiembre de 2019 Sin comentarios

Special Section in Optical Engineering about Spatial Light Modulators

A special section on Spatial Light Modulators (SLMs) – Devices and Applications will be published in the journal Optical Engineering. Ignacio Moreno and María Del Mar Sanchez-Lopez are Guest Editors of this special section of the journal, together with Prof. Andrew Forbes and Prof. Yoshio Hayasaky.

The following link leads to the journal Call for Papers.

The deadline for submitting papers is October 15th, 2019. See here the flyer of the OE special section on SLMs. OE-SLMs


Miércoles, 14 de agosto de 2019 Sin comentarios

New paper in Optics Letters on breaking the Nyquist limit for diffractive lenses with high phase modulation displays

OL FIGWe published a new paper in Optics Letters entitled Encoding lenses with focal lengths lower than the Nyquist limit using high phase-modulation displays. In this work we show that focal lengths much lower than the classical Nyquist limit can be encoded onto spatial light modulators having a large phase-dynamic range.

Experimental results are included with a display showing 10π phase modulation reducing the Nyquist limit by a factor of about 1/10. We used a  Hamamatsu reflective LCoS device designed for use in the near infra-red (NIR) range, but operated with visible light in order to achieve such large modulation regimes.

The work has been done in collaboration with our friends at the Department of Physics of San Diego State University.

Jueves, 27 de junio de 2019 Sin comentarios

New paper in Optics Express about a geometric phase vortex triplicator grating

REDWe published a new paper in Optics Express entitled Optimal triplicator design applied to a geometric phase vortex grating. It shows a liquid-crystal diffraction grating based on the optimal triplicator design fabricated as a geometric phase element. We analyze the polarization properties of this special diffraction grating and then use embedded spiral phases to design geometric phase vortex diffraction gratings. The fabrication of a two-dimensional version of such a design is demonstrated using a micro-patterned half-wave retarder, where the phase distribution is encoded as the orientation of the fast axis of the retarder.

This proof-of-concept element is made of liquid crystal on BK7 substrate where the orientation of the LC is controlled via photoalignment, using a commercially available fabrication facility. Experimental results demonstrate the parallel generation of vortex beams with different topological charge and different states of polarization.

This work is part of the PhD Thesis of David Marco, and it has been done in collaboration with our friends Aarón Cofré and Asticio Vargas, from Universidad de La Frontera, Temuco, Chile.

Categories: Projects, Publications, Research, Thesis Tags:

Lunes, 6 de mayo de 2019 Sin comentarios

New paper in J. Opt. Soc. Am. B about the colors of a tunable q-plate

DzexHWoW0AAiN98Our new paper in Journal of the Optical Society of America B is entitled Using birefringence colors to evaluate a tunable liquid-crystal q-plate. Here we show a tunable liquid-crystal commercial -plate from the company Arcoptix, operative in the visible and near-IR range. We study its spectral and color birefringence properties under broadband illumination.

We first characterize the spectral retardance function of the device in a wide range from 400 to 1600 nm and determine how it changes upon applied voltage.

Then we evaluate the color transmission characteristics when inserting the -plate between crossed and parallel linear polarizers. These color properties agree with the trajectory in the CIExy chromaticity diagram as the applied voltage changes.

Finally, we demonstrate that a simple visual inspection of the transmitted birefringence color perceived when placing the -plate between crossed polarizers can be used to obtain a rapid estimation of the -plate retardance at given wavelength ranges.

This work is the first paper of the PhD Thesis of David Marco.

Categories: Projects, Publications, Research, Students, Thesis Tags:

Miércoles, 13 de febrero de 2019 Sin comentarios

New paper in Optics Express about Guoy phase effects on the propagation of vector beams

GuoyOur new paper in Optics Express entitled Gouy phase effects on propagation of pure and hybrid vector beams reports a theoretical simplified model and experimental analysis of the Gouy phase effects on vector beams. Experimental results at various axial planes, before and past the focus, are obtained by using a simplified liquid-crystal spatial light modulator-based optical system that allows the easy generation of these beams. Furthermore, a new alternative optical set-up that is devoid of moving elements is demonstrated, which simplifies this study.

We experimentally verify the differences between pure and hybrid vector beams upon propagation. While the first ones remain stable, hybrid vector beams show Gouy phase effects that demonstrate an optical activity where the local polarization states rotate by an angle that depends on the propagation distance.

This study has been conducted in collaboration with our friends at San Diego State University, Prof. Jeffrey A. Davis and Prof. Don M. Cottrell.

Martes, 29 de enero de 2019 Sin comentarios

New paper in Optical Engineering about a holographic projection system

OEng2A new paper of ours is published in the journal Optical Engineering entitled Holographic projection system with programmable control of state of polarization, focus plane, and size of the reconstruction

This work presents a holographic projection system based on the encoding of computer-generated holograms onto a spatial light modulator. We show how the size, location, and polarization state of the output can be controlled completely electronically, without physically moving any element in the system. And we show that the system is capable to produce optical logical operations by superimposing two different images encoded onto orthogonal polarization states.

The work has been done with our friends at the Department of Physics at San Diego State University.


Jueves, 27 de diciembre de 2018 Sin comentarios

New paper in Optics & Lasers in Engineering with a geometric phase lens based system to analyze vector beams

VortexWe published a new paper in Optics & Lasers in Engineering entitled Geometrical-phase lens based optical system for the spin-splitting of vector beams

In this work we combine a geometric phase lens and a telescope system to produce an optical system with two polarization controlled real foci with equal magnification. And we apply it to characterize vortex beams and vector beams, splitting longitudinally the circular polarization components and focusing them into different axial planes.

This work was develop din collaboration with our friends Asticio Vargas and Fabián Torres-Ruiz, from Universidad de La Frontera, Temuco (Chile). And it is part of the PhD Thesis of Aarón Cofré.

Sábado, 14 de julio de 2018 Sin comentarios

Aarón Cofré presents his PhD Thesis on diffractive optics systems for the generation of optical vortices and structured polarized beams

AaronOn July 10th 2018, Aarón Cofré presented the defense of his PhD Thesis entitled Development of advanced diffractive systems for the generation of optical vortices and structured polarized beams.

The Thesis has been supervised by Ignacio Moreno and Asticio Vargas, and included various experimental studies on how to generate optical vortices and vector beams.

The results of the thesis resulted in four articles published in the journals European Journal of Physics, Optics & Lasers Technology, Optics Express and Optics & Lasers in Engineering respectively.

In the picture, Aarón with the supervisors and the members of the jury.




Miércoles, 11 de julio de 2018 Sin comentarios