Láseres de alta eficiencia basados en películas orgánicas delgadas: aplicaciones como sensores

This paper summarizes the most important results of the PhD Thesis presented by M. M-V. and directed by M.A. Díaz-García. Thin film organic lasers have demonstrated its applicability at laboratory scale, spectroscopy, optical communications, chemical sensing or biosensing. To bring optically-pumped solution processed thin film organic lasers to the real market the active material must be: able to emit at low pump excitation (low threshold), photostable to ensure a long operational lifetime; capable of emitting at various wavelengths or colours, processable by low-cost solution-based methods and mechanically flexible. We show all these properties amalgamated in a novel organic active materials: carbon-bridged oligo(p-phenylenevinylene)s (COPVn) dispersed in thermoplastic polymer films and a COPV-polymer prepared as a neat film. Novel devices by using different architectures have been optimized and studied. The high performance achieved with these laser devices has been demonstrated by pumping them with an inexpensive laser diode. The sensing applicability of thin film organic lasers has been also demonstrated by preparing and characterizing bulk refractive index sensors and biosensors.Este documento resume los resultados más importantes de la tesis doctoral presentada por M. M-V. y dirigida por M.A. Díaz-García. Los láseres orgánicos de película delgada se aplican a escala de laboratorio, espectroscopía, comunicaciones ópticas, detección química o biodetección. Para conseguir llevar este tipo de láseres de manera eficiente al mercado, el material activo ha de cumplir las siguientes características: capacidad de emitir al ser bombeando a baja energía, alta fotoestabilidad para garantizar una larga vida útil; capacidad de emitir a diferentes longitudes de onda o colores, procesabilidad por métodos de bajo coste y que el dispositivo sea mecánicamente flexible. Todas estas propiedades están presentes en un novedoso material orgánico activo basado en oligómeros con puente de carbono (COPVn) disperso en películas de polímero termoplástico. Se han optimizado y estudiado nuevos dispositivos mediante el uso de diferentes geometrías y resonadores, observando un alto rendimiento y logrando bombearlos con un simple diodo láser. Algunas aplicaciones de detección con estos dispositivos han sido demostradas: sensores de índice de refracción y biosensores.The PhD thesis described in this paper, has been supported by the Spanish Government, through projects: MAT2008-06648-C02-01 and MAT-2011-28167-C02-01, and FPI grant (BES-2009-020747). MMV also acknowledges support from the European Community (FEDER) and Junta de Castilla y León (JCYL) through Postdoctoral Fellowship (no. SA046U16), as well as, under a Postdoctoral project CDEIGENT/2018/024 (Generalitat Valenciana, Spain)

Time-stable holograms stored in hydrogel matrix

Storing holograms in hydrogel matrices and its temporal stability is real challenge when the material is immersed in aqueous medium. Hydrogels are 3D polymer networks capable of undergoing reversible volume changes. Since they can be synthesized to be sensitive to a range of relevant analytes, one of the most important applications of this type of system are holographic sensors. These sensors have great potential to be used in different areas such as environmental detection, veterinary testing, pharmaceutical bioassays, and medical diagnosis. Therefore, a key factor in the manufacture of holographic sensors is to develop and optimize hydrogel matrices in which stable holograms can be stored over time and in aqueous media where analytes are present.Thanks to the government of Algeria for the scholarship offered to develop my thesis in the Holography and Optical Processing Group of the University of Alicante, to the Spanish Ministerio de Ciencia e Innovación under project PID2019-106601RB-I00, to Generalitat Valenciana (Spain) CDIAGENT/2018/024, to IDIFEDER/2021/014 (potencial FEDER funding

Design and development of an innovative and simple optical sensor for the detection of acetic acid

The technology we are developing consists of the use of coordination compounds with metals to carry out this detection of Acetic acid. This compound normally reacts with acetic acid changing its colour, making it a suitable compound for use as a detector. The proposed method allows detecting acetic acid in any medium, whether in solution, in the gas phase, in the solid phase, or in any combination of these. Upon contact with the acid, a colour change occurs that can be detected visually or through optical means. After its use, the active medium can be regenerated by a simple procedure and be available again for new use. This allows the creation of simple and intuitive detection devices, usable by non-experts and that can be regenerated and reused. The main advantage of this sensor is to allow the specific detection of acetic acid and quantification of its concentration, using coordination compounds with metals that are present in the yellow dye.This work was supported by Ministerio de Ciencia e Innovación (Spain) under project PID2019-106601RB I00,and Generalitat Valenciana (Spain) under projects IDIFEDER/2021/014 (cofunded by European Union through the FEDER Programme), PROMETEO2021/006

Design and development of a simple and innovative Optical detection sensor for acetic acid

The technology we are developing consists of the use of coordination compounds with metals to carry out the detection of acetic acid, which is a harmful substance for human health and some art works.This work was supported by Ministerio de Ciencia e Innovación (Spain) under project PID2019-106601RB-I00, and Generalitat Valenciana (Spain) under projects IDIFEDER/2021/014 (cofunded by European Union through the FEDER Programme), PROMETEO 2021/006

Holographic Lens Resolution Using the Convolution Theorem

The similarity between object and image of negative asymmetrical holographic lenses (HLs) stored in a low-toxicity photopolymer has been evaluated theoretically and experimentally. Asymmetrical experimental setups with negative focal lengths have been used to obtain HLs. For this purpose, the resolution of the HLs was calculated using the convolution theorem. A USAF 1951 test was used as an object and the impulse responses of the HLs, which in this case was the amplitude spread function (ASF), were obtained with two different methods: using a CCD sensor and a Hartmann Shack (HS) wavefront sensor. For a negative asymmetrically recorded HL a maximum resolution of 11.31 lp/mm was obtained. It was evaluated at 473 nm wavelength. A theoretical study of object-image similarity had carried out using the MSE (mean squared error) metric to evaluate the experimental results obtained quantitatively.This research was funded by Universidad de Alicante (UAFPU20-23); Generalitat Valenciana (CIDEXG/2022/60, CDEIGENT/2018/024, IDIFEDER/2021/014, PROMETEO/2021/006); Ministerio de Ciencia e Innovación (PID2019-106601RB-I00, PID2021-123124OB-I00)

Holographic solar concentrators stored in an eco-friendly photopolymer

In this work it is shown the first characterization of holographic solar concentrators recorded in Biophotopol - one of the greenest photopolymers. Biophotopol is an acrylate-based and water-soluble photopolymer with good recycling properties. The composition of this photopolymer and their thickness are easily changeable, which implies an important advantage vs. others commercialized photopolymers. Good diffraction efficiency and wide acceptance angles are achieved on phase volume transmission holograms by using an optimized composition and thin layers. A curing stage with a white incoherent light has been performed to obtain high temporal stability together with a good diffraction efficiency. Finally, the performance of the holographic lenses as holographic solar concentrators has been evaluated with an electronic setup connected to a polycrystalline silicon photovoltaic cell and a high intensity solar simulator emitting a standard solar spectrum (AM1.5G).This work has financial support from: Ministerio de Ciencia e Innovación, Spain, under project PID2019-106601RB-I00 and FIS2017-82919-R/(MINECO/AE/FEDER, UE); Generalitat Valenciana, Spain, under project CDEIGENT/2018/024

CCD and Hartmann-Shack wavefront sensor to analyse holographic lens resolution

Nowadays, the study and optimization of volume holographic lenses (HLs) stored in low-toxicity photopolymers have a great interest. HLs are now a component of optical imaging systems that are mostly used in head-mounted displays for virtual and augmented reality or as non-image systems in light deflectors and concentrators. One of the most important parameters used when working with imaging systems is the resolution of the optical system. In this work, the similarity between the object and image of negative asymmetrical HLs stored in a low-toxicity photopolymer named Biophotopol has been evaluated theoretically and experimentally. For this purpose, the resolution of the HLs was calculated using the Convolution Theorem. A USAF 1951 test was used as an object and the impulse responses of the HLs were obtained with two different sensors: CCD and Hartmann-Shack (HS) wavefront sensor. In addition, the resolution of the HLs has been obtained by two different methods: one using the Convolution Theorem, using both the CCD and the HS wavefront sensor, and the other by forming the USAF test image on the CCD sensor. Finally, a theoretical study of object-image similarity was carried out using the MSE (mean squared error) metric to evaluate the quantitative experimental results.This research was funded by Universidad de Alicante (UAFPU20-23); Generalitat Valenciana (CIDEXG/2022/60, IDIFEDER/2021/014, PROMETEO/2021/006); Ministerio de Ciencia e Innovación (PID2019-106601RB-I00, PID2021-123124OB-I00)

Voltage dependence of retardance, flicker, and director angle orientation in reflective liquid crystal devices by average Stokes polarimetry

Parallel-aligned liquid crystal on silicon devices (PA-LCoS) can be found nowadays in most of the advanced areas in optics and photonics. Many works have been dedicated to their characterization for optimum utilization in applications. However, usual techniques are based on diffractive or interferometric measurements. Recently, we proposed the use of Stokes polarimetry for a versatile yet easy to implement characterization. We show that the LCoS can modelled as a nonabsorbent reciprocal device which, combined with time-average Stokes polarimetry, enables to demonstrate robust measurements across the whole applied voltage range for the retardance and its flicker. One of the main novelties is that we also obtain the director orientation, which we show that changes across the voltage range, especially at larger applied voltages. This might affect in very sensitive applications. It might also provide a deeper insight into the internal dynamics in the LC layer.Ministerio de Ciencia e Innovación, Spain (FIS2017-82919-R (MINECO/AEI/FEDER, UE); PID2019-106601RB-I00); Generalitat Valenciana, Spain (GV/2019/021; CDEIGENT/2018/024); Universidad de Alicante, Spain (UATALENTO18-10)

Ultrashort pulse propagation through depressed-cladding channel waveguides in YAG crystal: Spatio-temporal characterization

[EN]Inscription of optical waveguides by direct femtosecond laser irradiation has become a very versatile tool for the development of integrated photonic devices, such as waveguide lasers, frequency converters or photonic lanterns, among many others. The potential application of such devices for the control and manipulation of ultrashort pulses requires the precise knowledge of the temporal distortions that may be induced in the pulse propagation. Currently, research in this topic is scarce, and to our knowledge there is no previous experimental study on the spatio-temporal characterization at the output of waveguides inscribed inside crystals. Here, we have firstly fabricated depressed-cladding waveguides with different modal behavior in YAG crystal by direct femtosecond laser irradiation. Then, we implemented an experimental method based on the fiber coupler assisted spectral interferometry technique, that allows obtaining: (1) the temporal dispersion of a pulse at the output of an inscribed waveguide and, (2) full spatio-spectral and spatio-temporal characterization of the output of single-mode and multi-mode waveguides. Our results suggest that the main contribution to the pulse dispersion is due to the material dispersion. Moreover, we found that multimodal waveguides may induce an appreciable inhomogeneity in the temporal features of the pulses that needs to be taken into account in the design of complex devices.This work was supported by Junta de Castilla y León (Project SA046U16 and SA287P18) and MINECO (Projects FIS2017-87970-R, EQC2018-004117-P). M.M.-V. acknowledges support from Junta de Castilla y León grant (No. SA046U16) and from Generalitat Valenciana, Spain, under project CDEIGENT/2018/024

Shrinkage studies and optimization of multiplexed holographic lenses with high diffractive efficiency and wide angular response

Today, the advancement of optical systems that can harness clean and renewable energy sources is a major focus for researchers and innovators worldwide. As we strive to create a sustainable future, this challenge has become increasingly critical to our success. Fresnel lenses are widely used as traditional concentrators, but they have a small acceptance angle, and the reflective elements need continuous maintenance of the surface reflectivity. Transmitting Holographic Optical Elements (HOEs) are an alternative to conventional lenses because they are more economical and versatile. Their material is usually a flexible photopolymer so that the optical element can be attached to different types of support, depending on whether one type of handling is required or another, and they tend to have low weight and volume, as well as a simple way of manufacturing. In addition, also provide an extended focusing area which helps to protect solar cells from heating damage. A theoretical and experimental study on the shrinkage of multiplexed holographic lenses (MHL) that were stored in a low-toxicity photopolymer was carried out. To accomplish the study, a K-space tool was used. Furthermore, an optimization analysis of the angular distance between peaks was performed. To determine efficiency, an evaluation of the short-circuit current under solar illumination with varying incident reconstruction angles was done.This research was funded by Universidad de Alicante (UAFPU20-23); Generalitat Valenciana (CIDEXG/2022/60, IDIFEDER/2021/014, PROMETEO/2021/006); Ministerio de Ciencia e Innovación (PID2019-106601RB-I00, PID2021-123124OB-I00)