This work presents a complete polarimetric study of a twisted-nematic (TN) LC cell. We review the existing physical models and analyze the different modulation regimes. We extend the usual Jones matrix approach, where these microscopic physical models were developed, to the corresponding Mueller matrix approach. This polarimetric analysis is then used to obtain the effective linear and circular retardance components of the cell and to characterize its physical parameters like the twist angle, the orientation of the LC director axis and the maximum retardance. The technique simplifies previous approaches with the advantage of employing a single wavelength.
This work is part of the PhD Thesis of Esther Nabadda.
Here we show a ferroelectric liquid crystal (FLC) modulator with a non-standard large switching rotation angle, close to 90◦. The modulator acts as a switchable wave-plate with an in-plane rotation of the principal axis under the action of a bipolar voltage. The modulator is shown to behave as a binary 𝜋 phase modulator independently of the input state of polarization.
This work is part of the PhD Thesis of Esther Nabadda, and its has been done in collaboration with Dr. hab Noureddine Bennis and his collaborators at the Faculty of New Technologies and Chemistry of the Military University of Technology, Warsaw (Poland).
TecnOPTO participated in the meeting XXXVIII Bienal de Física, organized by RSEF – The Royal Spanish Society of Physics, this year held in Murcia from 11th to 15th of July 2022.
We contributed with two communications at the Symposium of Advanced Optics, presented by Esther Nabadda and María del Mar Sanchez respectively, as well as another communication to the Symposium on Women in Physics, presented by Pascuala García.
In addition, Pas was member of the Scientidic Committee, organized a Round Table and chaired the Symposium on Women in Physics.
On July 1st 2022, Dra. Guadalupe López Morales participated at the seminars of CIO – Centro de Investigaciones en Optica (México) by delivering the conference entitled «Polarimetría de imagen para la caracterización de materiales».
Here we demonstrate a technique to perform phase-shift interferometry of structured light. The interesting aspect is that the same SLM system used to generate the structured light is used, without no need of any additional element, to perform the phase-shift interferometry. A simple rotation of a polarizer transforms the system from the standard phase-modulation regime to the common-path polarization interferometer.
This paper is part of the PhD Thesis of Esther Nabadda.
This year Esther Nabadda attended the 2022 Siegman International School on Lasers, a week-long program covers all aspects of lasers and photonics. This year the School was organized by the University of Warsaw at Checiny (Poland), from 25th June to 2nd July 2022.
Esther attended the courses and presented her PhD work in progress entitled «Ferroelectric liquid crystal modulator with large switch rotation angle for polarization independent binary phase modulation»,work made in collaboration with Dr. Noureddine Bennis and his colleagues at the Military University of Technology of Warsaw.
Esther appears on the section «Amplify Black Voices in Optics» of OPTICA (former OSA), a section devoted to meet scientists and engineers from all over the world who represent Black achievement in science at every stage of their careers.
The technique is a reverse engineering method that does not require information about the microscopic physical parameters of the liquid-crystal material or details of the fabrication and electronics of the display. Instead, it is based on the overall effect on the diffraction efficiency of displayed binary phase gratings as a function of the addressed gray level. We show how the efficiency of the zero (DC) and first diffraction orders provides valuable information enough to identify and quantify the pixel crosstalk. The technique is demonstrated with a modern phase-only liquid-crystal on silicon (LCOS) spatial light modulator (SLM), illustrating the limitations that this effect imposes to the spatial resolution of the device and providing quantitative measurement of the impact on the diffraction efficiency.
The work has been done in collaboration with our colleagues Prof. Jeffrey A. Davis and Prof. Don M. Cottrell from San Diego State University.
Esther Nabadda completed a research stay at the Faculty of Advanced Technology and Chemistry of the Military University of Technology (WAT), in Warsaw. This stay is part of her PhD program and there she has been learning techniques for the production and characterization of different liquid-crystal optical modulators, under the supervision of Dr. hab Noureddine Bennis.
This stay was performed within the frame of the project NAWA PROM – «International scholarship exchange of doctoral candidates and academic staff» implemented at WAT.
David Marco completed his PhD studies with a public defense of his PhD Thesis entitled «Design and characterization of spatial light modulator optical systems and geometrical phase elements for the generation of structured light«, supervised by María del Mar Sánchez-Lopez and Ignacio Moreno.
The jury for the defense was composed by Dr. Gemma Piquero, from University Complutense of Madrid, Dr. Carlos Hernández, from University of Salamanca and Dr. Carlos R. Fernández-Pousa, from UMH.
Our last paper published in Optics and Laser Technology (OLT) is entitled Mueller matrix polarimetric analysis applied to characterize the physical parameters of a twisted-nematic liquid-crystal modulator.
