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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.


 

 


Categories: Publications, Research Tags:

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

New paper in Optics Express about dual polarization split lenses


OptExpressWe published a new paper in Optics Express where we report the realization of polarization sensitive split lens configurations. We propose and demonstrate the generalization of the split lens concept to vectorial split lenses, leading to light patterns with customized intensity and state of polarization. We demonstrate how these polarization split lenses can be experimentally implemented by means of an optical system using two liquid crystal spatial light modulators, each one phase modulating one orthogonal polarization component.

The proposed technique is a simple method to generate structured light beams with polarization diversity, with potential applications in polarimetry, customized illuminators or quantum optics.

This work has been published in Optics Express, entitled Dual polarization split lenses. The work has been developed in collaboration with our friends at the Departamento de Ciencias Físicas, Universidad de la Frontera (Chile) and our friends at Departamento de Física de la Universitat Autònoma de Barcelona. This is the third paper resulting from the Thesis of the PhD student Aarón Cofré.


 


Martes, 19 de septiembre de 2017 Sin comentarios

Pascuala García presents an SLM based optical microscope at the SPIE Optical Metrology Conference in Munich


SPIE PasPascuala Garcia presented the communication entitled “On axis programmable microscope using liquid crystal spatial light modulator” at the SPIE Optical Metrology Conference, held in Munich in June 25th to 29th, 2007.

In her presentation, she showed an optical microscope system we have developed, that includes an LCOS SLM display to perform opto-digital filtering on-axis. We use a Hamamatsu SLM, free of flickering, which can be tuned to fully eliminate the zero order component of the encoded diffractive filter, therefore making use of the full space-bandwidth. The system was demonstrated by implementing different optical processing operations based on phase-only gratings such as phase-contrast, band-pass filtering, additive and subtractive imaging, or Differential Interference Contrast (DIC) imaging.

A related manuscript is available at the SPIE Proceedings in Optical Methods for Inspection, Characterization, and Imaging of Biomaterials III, edited by Pietro Ferraro, Simonetta Grilli, Monika Ritsch-Marte, Christoph K. Hitzenberger, Proc. of SPIE Vol. 10333, 103330Q (2017). Link

 


Viernes, 21 de julio de 2017 Sin comentarios

New paper in OLT with a new polarization grating based single shot polarimeter


OLTWe developed a quantitative analysis of the performance of a complete snapshot polarimeter based on a polarization diffraction grating (PDGr). The work has been published in the paper entitled Quantitative performance of a polarization diffraction grating polarimeter encoded onto two liquid-crystal-on-silicon displays, published at the journal Optics & Laser technology.

The PDGr is generated in a common path polarization interferometer with a Z optical architecture that uses two liquid-crystal on silicon (LCoS) displays. The programmable PDGr is capable to act as a simultaneous polarization state generator (PSG), yielding diffraction orders with different states of polarization. The same system is also shown to operate as a polarization state analyzer (PSA), therefore useful for the realization of a snapshot polarimeter. We analyze its performance using quantitative metrics such as the conditional number.

This work has been developed in collaboration with our friends at the Departamento de Ciencias Físicas, Universidad de la Frontera (Chile) and our friends at Departamento de Física de la Universitat Autònoma de Barcelona. And it will part of the PhD Thesis of Aarón Cofré.


Miércoles, 14 de junio de 2017 Sin comentarios

New paper in Scientific Reports, with a polarization grating design for the section of vector beams


SciRep

We published a new paper in Scientific Reports entitled Vector Beam Polarization State Spectrum Analyzer. This work has been done with our friends at San Diego State University.

In this work we present a proof of concept for a vector beam polarization state spectrum analyzer based on the combination of a polarization diffraction grating (PDG) and an encoded harmonic q-plate grating (QPG). The result is a two-dimensional polarization diffraction grating that generates six different q-plate channels with topological charges from −3 to +3 in the horizontal direction, and each is split in the vertical direction into the six polarization channels at the cardinal points of the corresponding higher-order Poincaré sphere. Consequently, 36 different channels are generated in parallel.

We show that this system can be used as a vector beam polarization state spectrum analyzer, where both the topological charge and the state of polarization of an input vector beam can be simultaneously determined in a single experiment.

Download the paper here

 


Categories: Collaborators, Publications, Research Tags:

Viernes, 26 de mayo de 2017 Sin comentarios