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Solar concentrator systems represent an important challenge in our society for outstanding photovoltaic (PV) applications. Fresnel lenses or parabolic mirrors concentrate sunlight in a small solar cell surface. On the one hand, Fresnel lenses have an exceedingly small acceptance angle and require expensive tracking systems to follow the path of the Sun. On the other hand, conventional parabolic mirrors need periodic maintenance of the surface reflectivity. Holographic optical elements (HOEs) represent a suitable alternative to Fresnel lenses and solar reflectors, they are cheaper and more versatile. Particularly, multiplexed holographic solar concentrators (HSCs) give an insight into promising possibilities for Building-Integrated Concentrating PV (BICPV). A good trade-off between wide acceptance angle and high diffraction efficiency represents an important milestone in the area. Our research group obtained the higher acceptance angle in a multiplexed HSC design (Morales et. al. Opt. Express 30, 25366 (2022)). This design was composed of seven holographic multiplexed lenses in Biophotopol material with thick thickness, 197 μm. In the present work, more efficient holographic solar concentrators than previous works are shown. As far as we know, it has been obtained the best trade-off between high efficiency and wide acceptance angle HSC-PV solar cell systems. Generalitat Valenciana (CIDEXG/2022/60, IDIFEDER/2021/0.14, PROMETEO/2021/006); Ministerio de Ciencia e Innovación (PID2019-106601RB-I00; PID2021-123124OB-I00); Universidad de Alicante (UAFPU20-23).

The storage of time-stable holographic gratings in photohydrogels when the material is immersed in liquid media represents a great challenge at present. A very important stage in the process of storing holograms in photohydrogels are the washing stages to eliminate the remains of the components that have not reacted in the photochemical reaction. The main goal of this work is focusing on the study of the optimization of the washing stages of the photohydrogels based on acrylamide and N,N’-methylenebis(acrylamide) once unslanted transmission holograms have been stored. For the purpose of determining the compositions of the wash solutions, High-Performance Liquid Chromatography and UV-visible measurements have been employed in our system. PBST and DMSO:H2O 6:4 (v/v) are used as solvents in the washing stages. The diffraction efficiencies are measured during the washing stages and after the storing of the holograms during several days in PBST. Maximum diffraction efficiencies of 38.0 and 27.6% are reached when PBST and DMSO:H2O 6:4 are employed, respectively. Work funded by Ministerio de Ciencia e Innovación, Spain, under project PID2019-106601RB-I00; by Generalitat Valenciana under projects GRISOLIAP/2019/143, CIDEXG/2022/60, PROMETEO/2021/006, PROMETEO/2020/094 and IDIFEDER/2021/014 (co-funded by European Union through the FEDER Program), Spain. K. Berramdane thanks to the government of Algeria for her scholarship offered to develop her thesis in the Holography and Optical Processing Group at the University of Alicante (Spain). M. I. Lucío acknowledges her Juan de la Cierva Incorporación grant (IJC 2018-035355-I) funded by MCIN/AEI/10.13039/501100011033.

Unslanted reflection gratings has been stored in an acrylate-poly(vinyl alcohol) based photopolymer. The diffraction efficiency has been increased doping the photopolymer with platinum (Pt) nanoparticles. This research was funded by Ministerio de Ciencia, Innovación y Universidades, Spain, under project PID2019-106601RB-I00; Generalitat Valenciana, Spain, under projects CDEI-GENT/2018/024, PROMETEO/2021/006, and IDIFEDER/2021/014 (co-funded by European Union through the FEDER Programme); Universidad de Alicante, Spain. Predoctoral Fellowship UAFPU20-23.

Nowadays, the study and optimization of volume holography reflection gratings stored in environmentally compatible photopolymers has a great interest since they can be used as holographic optical elements. One of the main advantages of reflection holograms is that they can be reconstructed using white light. This allows to develop holographic sensors. Unslanted reflection holograms have been stored in an acrylate-poly(vinyl alcohol) based photopolymer development in our research group. With the main objective of increasing the diffraction effciency of reflection holograms, a series of chemical modifcations have been introduced in the same acrylated-based photopolymer. Specifcally, this material has been doped with Platinum nanoparticles (Pt-NP), increasing the refractive index modulation in the recorded diffraction gratings. 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).

The study of the optical properties and behaviour of holograms stored in hydrogel matrices when the material is immersed in liquid medium represent a very important challenge currently. Hydrogels are 3D polymer networks capable of undergoing reversible volume changes. These hydrogels can be chemically modified to obtain materials with different properties such as to be sensitive to a range of relevant analytes. Emergent applications require that the holograms stored in hydrogels be time-stable in a liquid medium. One of the most important applications of this type of system are holographic sensors. Holographic sensors have advantages over other types of sensors such as the possibility of miniaturization due to the use of holographic techniques, the ability to produce three-dimensional images, real-time quantification, possibility of low-cost mass manufacturing and label-free analyte- responsive. Due to these advantages, these sensors have great potential to be used in different areas such as environmental detection, veterinary testing, pharmaceutical bioassays and medical diagnosis. Therefore, the optical behaviour of the holograms and the optimization of the hydrogel’s matrices must be well studied. When volume phase holograms are stored in hydrogels matrices in liquid medium, the holographic planes can undergo a bending process that give rise to asymmetries in the lateral lobes around the Bragg angle. This bending affect to the diffraction efficiency, wavelength of maximum diffraction efficiency and the angular sensibility. These parameters are used as signal transducers in holographic sensors in transmission mode. The general aim of this work has been study the bending that is produced in the holographic planes when unslanted transmission volume phase holographic grating with a frequency of 1200 lines/mm have been stored in hydrogel matrices based on acrylamide (AA) and N,N'-methylenebisacrylamide (MBA) using different solvents (dimethyl sulfoxide, water and buffer solution) during the manufacturing process. Considering previous works on bending, and grating attenuated hologram. This work was supported by the by “Generalitat Valenciana” of Spain (projects PROMETEO/2021/006 and IDIFEDER/2021/014, cofunded by European Union through the FEDER Programme) and by the “Ministerio de Ciencia e Innovación” of Spain (projects FIS2017-82919-R and PID2019-106601RB-I00).

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)