Characterization of registered holographic lenses in a photopolymer compatible with the environment

En este trabajo se presenta un dispositivo para obtener lentes holográficas (LH) en un fotopolímero compatible medioambientalmente sensibilizado a la longitud de onda de 488 nm. Utilizando este dispositivo se han obtenido LH's, reconstruidas con dos láseres 473 nm y 633 nm), de la misma focal y diámetro, con montajes experimentales simétricos y asimétricos, y positivas y negativas. La calidad de imagen de dichas lentes se ha evaluado: experimentalmente; a partir del cálculo de la MTF y las aberraciones obtenidas capturando con un sensor CCD la imagen del foco (PSF), y teóricamente; mediante software. También se propone un método para mejorar la calidad de imagen de las LH's que tienen más aberraciones.In this work it is presented a device to obtain holographic lenses (LH) in an environmentally compatible photopolymer sensitized at the wavelength of 488 nm. Using this device, LHs reconstructed with two lasers (473 nm and 633 nm), of the same focal and diameter have been obtained, with symmetrical and asymmetric experimental setups, and positive and negative focal. The image quality of these lenses is evaluated: experimentally; from the calculation of the MTF and aberrations, obtained by capturing the image of the focus (PSF) with a CCD sensor, and theoretically; by means of software. It is also proposed a method to improve the image quality of LH's that have more aberrations.Ministerio de Economía y Competitividad bajo los proyectos FIS2014-56100-C2-1-P, FIS2015-66570-P (MINECO/ FEDER) y FIS2017-82919-R (MINECO/ AEI/ FEDER/ UE); Generalitat Valenciana bajo los proyectos PROMETEOII/2015/015, ISIC/2012/013 y Universidad de Alicante bajo la ayuda AII2017-12

Holographic Lenses in an Environment-Friendly Photopolymer

In this paper, we theoretically and experimentally evaluated the quality of volume phase transmission lenses stored in an environmentally friendly photopolymer. Holographic lenses (HLs) were obtained using symmetrical and asymmetrical experimental setups with the same positive and negative focal length and pupil diameter. The image quality was evaluated from the calculation of the modulation transfer function (MTF) by capturing the point spread function (PSF) with a charge-coupled device (CCD). A maximum frequency of 14 L/mm, reaching an MTF value of 0.1, was obtained for a negative asymmetrically recorded HL, evaluated at 473 nm wavelength. A theoretical study of aberrations was carried out to qualitatively evaluate the experimental results obtained.Ministerio de Economía, Industria y Competitividad (Spain) (FIS2015-66570-P and FIS2017-82919-R); Generalitat Valenciana (Spain) (PROMETEO II/2015/015); Universidad de Alicante bajo ayuda AII2017-12

Holographic lenses stored in Biophotopol

Innovative technologies demand versatile and environmentally compatible optical elements. In this paper we evaluated the quality of volume phase transmission lenses stored in a biocompatible photopolymer. Holographic lenses (HL) have been obtained with the same focal and diameter, for a symmetric and asymmetric experimental setups, and positive and negative focal. The quality of these lenses have been evaluated: theoretically and experimentally, from the calculation of the modulation transfer function (MTF) by capturing the point spread function (PSF) with a CCD sensor. The HLs that have shown better quality are the negative asymmetrically recorded compared with the theoretical ones.Ministerio de Economía, Industria y Competitividad (Spain) (FIS2017-82919-R and FIS2015-66570-P); Generalitat Valenciana (Spain) (PROMETEO II/2015/015; Universidad de Alicante Ayuda AII2017-12

Roadmap on holography

From its inception holography has proven an extremely productive and attractive area of research. While specific technical applications give rise to 'hot topics', and three-dimensional (3D) visualisation comes in and out of fashion, the core principals involved continue to lead to exciting innovations in a wide range of areas. We humbly submit that it is impossible, in any journal document of this type, to fully reflect current and potential activity; however, our valiant contributors have produced a series of documents that go no small way to neatly capture progress across a wide range of core activities. As editors we have attempted to spread our net wide in order to illustrate the breadth of international activity. In relation to this we believe we have been at least partially successful

Tunable Waveguides Couplers Based on HPDLC for See-Through Applications

Photopolymers have become an important recording material for many applications, mainly related to holography. Their flexibility to change the chemical composition together with the optical properties made them a versatile holographic recording material. The introduction of liquid crystal molecules in a photopolymer based on multifunctional monomer provides us the possibility to generate tunable holograms. The switchable holographic elements are a key point for see-through applications. In this work, we optimize the holographic polymer-dispersed liquid crystals composition to improve the performance of tunable waveguide couplers based on transmission gratings and specifically their response under an applied electric field. A variation around 60% in the transmission efficiency was achieved.This research was funded by the “Ministerio de Ciencia e Innovación” (Spain) under projects FIS2017-82919-R (MINECO/AEI/FEDER, UE) and PID2019-106601RB-100), and by Generalitat Valenciana, Spain, under project CDEIGENT/2018/024

Analytical modeling of blazed gratings on two-dimensional pixelated liquid crystal on silicon devices

Phase spatial light modulators and, in particular, parallel-aligned liquid crystal on silicon (PA-LCoS) microdisplays are widely used to display programmable diffractive optical elements (DOEs). These are pixelated elements with inherent different characteristics when compared with DOEs produced with micro-optics fabrication techniques. Specifically, programmable DOEs may be affected by the fill factor, time-flicker, fringing-field and interpixel cross talk effects, and limited and quantized modulation depth of the LCoS device. Among the multilevel DOEs, we focus on the important case of the blazed gratings. We develop the corresponding analytical expressions for the diffracted field where, as novelties of this work, fill factor and flicker are introduced together with phase depth and the number of quantization levels. Different experimental-based normalizations are considered, which may lead to wrong conclusions if the fill factor is not considered in the expressions. We also analyze the differences arising between one- and two-dimensional pixelated devices. When compared with numerical procedures, our approach provides an analytical expression that facilitates the design, prediction, and discussion of experiments. As an application, we prove, for the limiting case of no interpixel cross talk, that multiorder DOEs cannot be more efficient than the equivalent single-order DOE. We also show how the results for DOEs with a unit fill factor can be adapted to DOEs with a fill factor smaller than one with a very efficient procedure.This work was funded by Ministerio de Economía, Industria y Competitividad (Spain), projects FIS2017-82919-R (MINECO/AEI/FEDER, UE) and FIS2015-66570-P (MINECO/FEDER); by Generalitat Valenciana (Spain), project PROMETEO II/2015/015 and GV/2019/021; and Universidad de Alicante (Spain), project GRE17-06

Caracterización de lentes holográficas registradas en un fotopolímero compatible medioambientalmente

En este trabajo evaluamos la calidad de lentes holográficas de volumen almacenadas en un fotopolímero respetuoso con el medio ambiente llamado Biophotopol. Las lentes holográficas (HL) se han obtenido en configuraciones experimentales simétricas y asimétricas con distancia focal negativa. La calidad de estas lentes se ha evaluado calculando la función de transferencia de modulación (MTF) para dos longitudes de onda (473 y 633 nm). Las HL que han demostrado una mejor calidad de imagen son las registradas asimétricamente y evaluadas a 473 nm.FIS2015-66570-P (Mineco/FEDER) y FIS2017-82919-R (Mineco/FEDER), Spain; PROMETEO II/2015/015 (Generalitat Valenciana, Spain); Universidad de Alicante bajo ayuda AII2017-12