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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

New paper on Optics Letters with a design for an achromatic retarder system with tunable retardance


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We published a new paper in Optics Letters entitled Achromatic linear retarder with tunable retardance.

In this work we present a universal design and proof-of-concept of a tunable linear retarder of uniform wavelength response in a broad spectral range. It consists of two half-wave retarders (HWR) between two quarter-wave retarders (QWRs), where the uniform retardance can be tuned continuously by simply rotating one of the HWRs. A proof-of-concept of this design is built by using commercially available Fresnel rhomb retarders that provide retardation with almost wavelength uniformity in the visible and near infrared from 450 to 1550 nm. The system is experimentally demonstrated to control the state of polarization of a super-continuum laser.

The work has been developed in collaboration with Asticio Vargas, from Universidad de la Frontera, Chile. And it is part of the PhD thesis of Abdelghafour Messaadi.


Sábado, 7 de julio de 2018 Sin comentarios

New paper in Applied Sciences about a zoom lens system without moving elements using SLMs


ZoomA new paper has been published entitled Programmable zoom lens system with two spatial light modulators: Limits imposed by the spatial resolution, published in the journal Applied Sciences, in a special issue devoted to liquid crystal on silicon devices.

This paper deals with the realization go a zoom lens system that used two liquid-crystal SLMs, so different magnifications can be obtained without any moving elements, simply by changing the focal length of the lenses displayed in each SLM. We include results with positive and negative magnifications. And we analyze the limits imposed by the limited spatial resolution of the SLMs.

The work has been developed at the Department of Physics at San Diego State University, with the participation of Ignacio Moreno.


Miércoles, 20 de junio de 2018 Sin comentarios

New paper in Optics & Laser Technology on the use of commercial q-plates at different wavelengths


S plateA new paper in the journal Optics & Laser Technology entitled Spectral performance of a zero-order liquid-crystal polymer commercial q-plate for the generation of vector beams at different wavelengths.

It deals with the use of liquid-crystal polymer q-plates operated at different wavelengths. We show how a broadband spectral characterization allows identifying the wavelengths with retardance values relevant for vector beam generation (ππ/2, and 3π/2). The wavelength is then used as a tuning parameter to change the device performance from the standard half-wave q-plate to a positive or a negative quarter-wave q-plate.

We present a simple procedure to derive the polarization distribution of the generated vector beams, and show that they can produce hybrid vector beams when operated at non-design wavelenths. Therefore, these results could extend the use of commercial q-plates for multicolour vector beam applications.

This work has been done in collaboration with Prof. Jeffrey A. Davis and Isaiah Abella, from San Diego State University.


 


Miércoles, 25 de abril de 2018 Sin comentarios

New paper in Optics & Lasers in Engineering with a self-calibration technique for a LCoS display


OLEA new paper published in Optics & Lasers in Engineering presents an experimental method to calibrate a liquid crystal on silicon (LCoS) display by using split-lens configurations displayed on the device. The split-lens directly generates an interference pattern from which the phase modulation is calculated. Additionally, a micro-lens array is displayed on the LCoS, within the same experimental set-up, to implement a Shack-Hartmann wavefront sensor and retrieve the display surface deformation.

This work is entitled LCoS display phase self-calibration method based on diffractive lens schemes, and has been developed by our collaborators at Universitat Autònoma de Barcelona, with the participation of Ignacio Moreno.


 


Domingo, 18 de marzo de 2018 Sin comentarios

New paper in Optics Express with a new technique to encode complex-valued holograms onto phase-only displays


ÑA new paper in Optics Express has been published entitled Random technique to encode complex valued holograms with on axis reconstruction onto phase-only displays, by José Luis Martínez-Fuentes and Ignacio Moreno.

This work presents a new technique to encode complex-valued holograms onto a phase-only display, based on a random selection determined by the amplitude level. The proposed technique offers some interesting features like on-axis hologram reconstruction, no iterative calculation, and good efficiency and good computational cost.

We provide here experimental results with computer generated holograms, as well as the generation of Hermite-Gauss and Laguerre-Gauss beams.


 

 


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Miércoles, 28 de febrero de 2018 Sin comentarios

New paper in Applied Optics with a q-plates designs with non-linear angular distribution of the principal axis


APPL OPTWe published a new paper in Applied Optics entitled Q-plates with a nonlinear azimuthal distribution of the principal axis: application to encoding binary data. This work has been developed with out colleagues at San Diego State University.

Here we use the optical system developed at SDSU to control two linear polarization components to encode q-plates where the angular orientation of the principal axis is varied spatially with a nonstandard distribution. We consider two cases: first, where the principal axis distribution is like an inverse-tangent function of the azimuth; and second, where it displays linear and flat segments. This last case is proposed as a new method for encoding binary data into the azimuthal lobes of the vector beam.

The use of the spatial light modulator based system allows these new and exotic q-plate designs without the difficulty of fabricating individual plates. Experimental results are presented.


 


Miércoles, 21 de febrero de 2018 Sin comentarios

New paper in Journal of Biophotonics about imaging biological tissues based on the indices of polarimetric purity


IPPsWe participated in a new paper published in Journal of Biophotonics entitled Polarimetric imaging of biological tissues based on the indices of polarimetric purity.

This work has been developed by our friends at Universitat Autònoma de Barcelona in the frame of the common coordinated collaboration project.

In this work we use the indices of polarimetric purity (IPPs) for the inspection of biological tissues.

Compared with standard polarimetric images of biological samples, IPP-based images lead to larger image contrast of some biological structures and to a further physical interpretation of the depolarizing mechanisms inherent to the samples.


 


Jueves, 4 de enero de 2018 Sin comentarios

New paper in Optical Engineering about parallel multiple imaging with a polarization diffraction grating


OptEngA new paper entitled Multichannel polarization imaging with a polarizing diffraction grating has been published in Optical Engineering. The work has been done in collaboration with our friends at the Department of Physics at San Diego State University (SDSU).

The work demonstrates a method to generate multiple imaging with polarization state diversity, based on the use of  a polarization diffraction grating design. The polarization grating is demonstrated in an SLM-based optical system developed at SDSU. We demonstrate the generation of six diffraction orders that encode six different polarization transformations. This technique can be useful for producing single-shot imaging polarimeters.


 

 

 


Viernes, 10 de noviembre de 2017 Sin comentarios