Antonio Fimia

• Professor
• Miguel Hernández University of Elche

Current cortical visual prosthesis approaches are primarily unidirectional and do not consider the feed-back circuits that exist in just about every part of the nervous system. Herein, we provide a brief overview of some recent developments for better controlling brain stimulation and present preliminary human data indicating that closed-loop strat...

We experimentally demonstrate how to accurately retrieve the refractive index profile of photonic structures by standard diffraction experiments and use of the rigorous coupled-wave analysis in the multi-wave coupling regime, without the need for taking any auxiliary data. In particular, we show how the phases of the Fourier components of a periodi...

The red palm weevil (RPW), Rhynchophorus ferrugineus, is one of the worst palm pests worldwide. Our study aims to assess its internal and external morphological response to a sudden but transient decrease in the environmental temperature. Wild pre-pupae were subjected for 7 days to either low (5.0 ± 0.5 °C) or ambient temperature (23 ± 1 °C). Such...

We experimentally demonstrate how to solve the phase problem of diffraction using multi-wave interference with standard diffraction experimental setups without the need for taking any auxiliary data. In particular, we show that the phases of the Fourier components of a periodic structure can be fully recovered by deliberately choosing a probe wavel...

The interaction of laser light with biological samples acquires increasing importance due to its numerous applications in areas like optogenetics or biophotonics. For many of these applications, it is important to know how light interacts with biological material, if it’s possible to quantify absorption and scattering effects produced and if these...

Silver halide sensitized gelatin (SHSG) processes are interesting because they combine the spectral and energetic sensitivity of a photographic emulsions with good optical quality and high diffraction efficiency of dichromate gelatin (DCG). Previous papers had been demonstrated that it is possible to obtain diffraction efficiencies near to 90% with...

Silver halide emulsions have been considered one of the most energetic sensitive materials for holographic applications. Nonlinear recording effects on holographic reflection gratings recorded on silver halide emulsions have been studied by different authors obtaining excellent experimental results. In this communication specifically we focused our...

In this paper we report on the use of digital holographic microscopy for 3D real time imaging of cultured neurons and neural networks, in vitro. Digital holographic microscopy is employed as an assessment tool to study the biophysical origin of neurodegenerative diseases. Our study consists in the morphological characterization of the axon, dendrit...

Time-delay of transmitted pulses with respect to the incident pulse in bacteriorhodopsin films has been studied without the use of a pump beam. Based on a modified saturable absorber model, analytical expressions of the transmitted pulse have been obtained. As a result, time delay, distortion and fractional delay have been analyzed for sinusoidal p...

Time-delay of transmitted pulses with respect to the incident pulse in bacteriorhodopsin films has been studied without the use of a pump beam. Based on a modified saturable absorber model, analytical expressions of the transmitted pulse have been obtained. As a result, time delay, distortion and fractional delay have been theoretically analyzed fo...

An energetic study of focused ultrashort Gaussian beams was carried out using the Fresnel diffraction formulae in the frequency domain. Analysis of the encircled energy at the focused plane shows that diffraction spreading of a focused pulsed beam occurs in the limiting case of a ultrashort pulse by comparing it to a cw beam whose frequency is omeg...

We present our first experimental results of lens irradiation obtained with ultrashort pulse lasers. The irradiation was done with the Ti:Safire laser which irradiates at 800 nm with a repetition rate of 76 MHz. The maximum average intensity used was 300mW, with pulses of 4 nJ. The holographic images obtained have given us information about the foc...

In this work we are going to apply GPU (Graphical Processing Units) with CUDA environment for scientific calculations, concretely high cost computations on the field of digital holography. For this, we have studied three typical problems in digital holography such as Fourier transforms, Fresnel reconstruction of the hologram and the calculation of...

The propagation of sinusoidal pulses in bacteriorhodopsin films has been theoretically analyzed using a complete study of the photoinduced processes that take into account all the physical parameters, the coupling of rate equations with the energy transfer equation and the temperature change during the experiment. The theoretical approach was compa...

We report on the performances measured at room temperature, before and after a cryogenic cooling cycle, of a set of NIR Volume Phase Holographic Gratings (VPHGs) manufactured at the Miguel Hernández University (UMH, Elche, Spain) aimed at their use in astronomical instrumentations. VPHGs are novel optical components which can replace standard ruled...

Protein Bacteriorhodopsin (bR) is one of the most promising and widely studied biomaterials for photonic applications like optical storage, modulation devices and photosynthetic light energy transduction. In this paper, we present the corresponding experimental results when pH-controlled modifications of bR doped polymeric films are realized in ord...

Digital Holographic Microscopy (DHM) is a potentially non-invasive new technology which can be applied in many areas from applied imaging science to biomedical optics. DHM is an interferometric technique that gives us a number of important advantages such as the possibility to acquire holograms at high speed, to obtain complete information about am...

Combined chemo and photothermal therapy in in vitro testing has been achieved by means of multifunctional nanoparticles formed by plasmonic gold nanoclusters with a protecting shell of porous silica that contains an antitumor drug. We propose a therapeutic nanoplatform that associates the optical activity of small gold nanoparticles aggregates with...

We analyze the near-field focalization properties of perfect black Fresnel Zone Plates (FZPs) through the exact solu- tions of Maxwellequations for radially polarizedfields obtained by means of Luneburg vector diffraction theory. The electromagnetic fields are computed assuming Hermite-Gauss and Bessel-Gauss beams as boundary conditions at the FZP...

In this work, we present the analysis of a photopolymerizable system based on pyrromethene dye (PM567) acting as a photoinitiator and HEMA as monomer both of them dissolved in a dry polymeric matrix of PMMA. Previously, we reported the recording of diffraction gratings in this composition, resulting in diffraction efficiencies near 60 % with exposu...

The aim of this work is to analyze the effect of the addition or substitution of several components (coinitiator and photoinitiator) in a photopolymerizable holographic material based on a pyrromethene dye (PM567) acting as a photoinitiator and HEMA as monomer both of them dissolved in a dry polymeric matrix of PMMA. For this, diffraction gratings...

The multiplexing of holographic reflection gratings with a spatial frequency higher than 5400 lines/mm in photopolymerizable sol-gel materials is experimentally demonstrated. The effect of the angular separation of the gratings and exposure time is characterized. Moreover, 9 reflection gratings are angularly multiplexed with diffraction efficiencie...

Silver halide materials have occupied an important place in the recording of images. The reason is mainly given by the high sensitivity of the recording medium, thus permitting the use of minimal levels light and hence easing the stability problems of apparatus and the need for high powered laser equipment. When the film is exposed in a holographic...

We present a holographic system that can be used to manipulate the group velocity of light pulses. The proposed structure is based on the multiplexing of two sequential holographic volume gratings, one in transmission and the other in reflection geometry, where one of the recording beams must be the same for both structures. Analytical expressions...

We present a holographic system that can be used to manipulate the group velocity of light pulses. The proposed structure is based on the multiplexing of two sequential holographic volume gratings, one in transmission and the other in reflection geometry, where one of the recording beams must be the same for both structures. As in other systems suc...

Near-field focusing properties of perfect black Fresnel zone plates are analyzed by solving Maxwell equations using the vectorial angular spectrum representation and the equivalent Rayleigh diffraction formulae of the first kind given by the Luneburg vector diffraction theory. Linear and circular polarizations are compared. As a result, an exact an...

Near-field focusing properties of perfect black Fresnel zone plates are analyzed by solving Maxwell equations using the vectorial angular spectrum representation and the equivalent Rayleigh diffraction formulae of the first kind given by the Luneburg vector diffraction theory. Linear and circular polar- izations are compared. As a result, an exact...

To evaluate the postoperative ocular optical quality using a double-pass method and assess visual outcomes in eyes with an apodized multifocal intraocular lens (IOL) and to correlate the findings with IOL power. Vissum Corporation, Alicante, Spain. Case series. This study evaluated eyes that had cataract surgery with implantation of an AcrySof ReST...

The recent results reported in reference [1] have produced an increased interest in explaining deviations from the ideal behavior of the energetic variation of the diffraction efficiency of holographic gratings. This ideal behavior occurs when uniform gratings are recorded, and the index modulation is proportional to the energetic exposure. As a re...

We theoretically analyze Airy beams by solving the exact vectorial Helmholtz equation using boundary conditions at a diffraction aperture. As result, the diffracted beams are obtained in the whole space; thus, we demonstrate that the parabolic trajectories are larger than those previously reported, showing that the Airy beams start to form before t...

We demonstrate that a periodic binary fiber grating (PBFG) formed by a sequence of two alternating homogeneous layers can be designed to generate flat-top optical pulses by reflection. For this purpose, specific design criteria allow an exact PBFG reflectance that approaches a sinc function with linear phase. Our design provides large layer thickne...

Present and future of holography depends on the development of high quality holographic recording media. In this sense, the improvement of most of the applications associated with holography can be attributed to the optimization of the recording step in material. In this work we review holographic recording media as silver halide, photopolymers and...

Present and future of holography depends on the development of high quality holographic recording media. In this sense, the improvement of most of the applications associated with holography can be attributed to the optimization of the recording step in material. In this work we review holographic recording media as silver halide, photopolymers and...

We theoretically and experimentally analyze the angular selectivity curves of nonuniform gratings recorded in a photopolymerizable silica glass. Due to the rigidity of this material, shrinkage would not cause fringe bending, so we propose that the coupling of the beams at the recording stage (two-wave mixing) produces the resulting nonuniformities....

The aim of this work was to perform a complete study of the dynamic and steady-state photoinduced processes of thick bacteriorhodopsin (bR) films, taking into account all the physical parameters and the coupling of rate equations with the energy transfer equation. The theoretical approach was compared with experimental data, and good concordance wa...

A matrix method which relates the field and its derivative is presented for the study of wave propagation in any type of one-dimensional media. The transfer matrix is obtained from the canonical solutions of Helmholtz equations at normal incidence. The method is applied to different optical systems like a Fabry-Perot cavity formed by uniform fiber...

The recording of holographic reflection gratings with a spatial frequency higher than 5400 lines ∕ mm in photopolymerizable solgel materials is experimentally demonstrated. Diffraction efficiencies near 60% and a FWHM of 2.5 nm centered at 531.5 nm are achieved. Moreover, the effect of the energetic exposure is characterized at different recording...

Recently the capability of photopolymerizable sol–gel materials to angular multiplex holographic gratings has been demonstrated [1, 2]. In this study, holographic transmission gratings were recorded using angular multiplexing in a silica glass doped photopolymer holographic recording material. The time interval between exposures and the angular sel...

A method based in the application of Fixed Point Theorem (FPT) techniques to the solution of the 1D wave equation at normal incidence for materials that present a continuous (real or complex) dielectric constant is presented. As an example, the method is applied for the calculation of the electric field, reflection and transmission spectra in volum...

A theoretical study of light-induced modulation of the dielectric permittivity in bacteriorhodopsin films has been done (including B--> M and B --> Q transitions). Analysis of dielectric permittivity modulation enables us to determine the fundamental limits of BR to be used in a holographic data storage system, together with the optimum experimenta...

We present the results obtained using two different types of the new panchromatic ultra-fine grain emulsion BBVPan, manufactured by Colourholographics Ltd. The first emulsion type was manufactured by mixing three monochromatic precipitates, so that each silver halide grain is sensitised with one dye only. The second emulsion was obtained by making...

In recent years the interest shown in dry photopolymer films as holographic recording materials have increased dramatically. The main reasons for this are the special properties of these media, such as high diffraction efficiency, low noise, real-time processing and low cost. Moreover, these materials are an important option for displays, high dens...

In this paper we have studied the recording of Fourier holograms in a PVA-AA photopolymer, analysing the influence of beam ratio in the quality of the reconstructed images. As a result, it has been observed that the variation of the beam ratio produces significant changes in the response of the material, showing that there is a range of optimal val...

In this paper, we present a photopolymerizable material in a sol-gel matrix suitable for recording a large number of multiplexed diffraction gratings with low total exposure energy. The matrix of this material is an inorganic porous silica glass, a material that does not shrink when radical photopolymerization is initiated. The photosensitive compo...

In this communication we present theoretical calculations of the optical properties for oriented bacteriorhodopsin films. Macroscopic optical properties of the film were related with the microscopic properties of the bacteriorhodopsin, which has been calculated using density functional method. Using the calculated optical properties, we had simulat...

Holographic techniques have been used for manufacturing multiple band one-dimensional, two-dimensional, and three-dimensional photonic crystals with different configurations, by multiplexing reflection and transmission setups on a single layer of holographic material. The recording material used for storage is an ultra fine grain silver halide emul...

A complete characterization of unslanted holographic reflection gratings with high diffraction efficiency recorded on ultrafine grain emulsion BB640 has been achieved. By use of a wavelength-dependent absorption coefficient, the diffraction efficiency, the replay wavelength, and the spectral bandwidth of each recording has been obtained. Correspond...

Three multiplexed holographic gratings were used to fabricate 3D photonic crystals without complete band gap using ultra-fine grain holographic emulsion as the storage material. Theoretical and experimental studies were carried out in order to characterize the crystals. Good agreement between theory and experimental results was obtained, showing th...

We describe the recording of holographic gratings in a photopolymerizable sol-gel glass based on acrylamide as monomer, triethanolamine as coinitiator, and yellowish eosin as photoinitiator. Although acrylic monomers have been introduced in silica glass by Cheben and Calvo [Appl. Phys. Lett. 78, 1490 (2001)], the well-known acrylamide based composi...

Photonic band structures of one-dimensional photonic crystals with an amplitude-modulated dielectric constant in the unit cell were studied. With this structure two bandgaps in the visible and one in the IR region were predicted. Experimental measurements of the two photonic bandgaps in the visible spectrum were made in a photonic crystal recorded...

In this paper, we describe a photopolymerizable silica glass based on acrylamide (AA) and N,N’-methylenebisacrylamide (BMA) as monomers, triethanolamine (TEA) as coinitiator and yellowish eosin (YE) as photoinitiator. We studied different compositions, analyzing the diffraction efficiency, energetic exposure and effective thickness obtained in the...

The gap created in the last decade in the market of fine and ultra-fine grain silver halide emulsions with the withdrawal of the historical producers was filled in recent years with new products and manufacturers. We have studied with holographic techniques the emulsion BB640, with a mean grain size of 20 nm, and we have found out that we can easil...

We present the results obtained using the new panchromatic ultra-fine grain emulsion BBVPan, manufactured by Colourholographics Ltd., to produce multiple band holographic reflection gratings, multiplexed on a single layer of material. Three different laser systems were used: He-Cd, frequency-doubled Nd-YAG and He-Ne. High diffraction efficiencies,...

The holographic parameters of purple membrane-polyacrylamide films obtained from a mutant form of Halobacterium salinarum (originally Halobacterium halobium) were measured. The synthesized films have an absorption of around 2.5 at 532 nm and a pH of 8.65. The results show that diffraction efficiencies of about 1.2 % (measured at 633 nm) can be achi...

A simple photopolymerizable dry polymeric film based on pyrromethene dye (PM567) which it has been usually used in solid-state dye lasers, has been developed. This new composition is based on only three components: poly-(methylmethacrylate) (PMMA) as a binder, 2-hydroxyethylmethacrylate (HEMA) as a monomer and 1,3,5,7,8-pentamethyl-2,6-diethylpyrro...

In this work we expose the results obtained with a wide variety of phase holographic recording materials that we have characterized in the range of low spatial frequencies (≤ 32 lines/millimeter). We have considered bleached photographic emulsion, silver halide sensitized gelatin and dichromated gelatin. This low spatial frequency characterization...

This work describes the study of free-radical homopolymerization kinetics for a system based on acrylamide, triethanolamine, and methylene blue on a polyvinylalcohol matrix, by analyzing temporal variations of the diffraction efficiency. Due to the high viscosity of the material, it has been demonstrated that diffusion processes at the time of reco...

Acrylamide-based holographic recording materials have significant advantages and the composition of these materials has been optimized in terms of energetic sensitivity and diffraction efficiency. As a result, diffraction gratings with an efficiency of almost 80% for energetic exposures of 35 mJ/cm2 and a spatial frequency of 1000 lines/mm in photo...

Accurate recording of computer-generated holograms (CGH) on a phase material is not a trivial task. The range of available phase materials is large, and their suitability depends on the fabrication technique chosen to produce the hologram. We are particularly interested in low-cost fabrication techniques, easily available for any lab. In this work...

Nonlinear recording effects on holographic reflection gratings recorded on BB640 emulsions have been studied. Using an analyticalapproach to the characteristic curve of these emulsions, we obtained the recorded density profiles corresponding to the original light pattern generated by the holographic setup. The final spatial profiles of the refracti...

In this work we have studied the characteristics of reflection gratings recorded with BB640 emulsions from Colourholographics Ltd. processed with a set of different developers and bleaching techniques. Overall diffraction efficiencies evaluated with spectral response curves result in values higher than 70% (80% taking into account reflection losses...

Photographic emulsions based on silver halide grains and their developers are characterized by the H-D curve, relating density with exposure. The H-D curve depends on a number of parameters from both of the emulsion and of the developing process, and always has a typical shape. In this study we present a H-D curve obtained with an ultra fine emulsi...

In this study the diffraction efficiency of diffuse-object holograms is compared with that of holographic gratings for a constant beam ratio and different intensities in order to analyzed the storage and reconstruction process with the same wavelength. When we work with the same wavelength in the register and reconstruction process, the refraction...

Bleaching is one of the key processes in the production of phase holograms with fine grain silver halide emulsions. This step was widely studied for discontinued Kodak, Agfa, and Ilford emulsions, and most of those results have been optimized with small changes for presently available holographic emulsions. A study of the different bleaching techni...

Polyvinylalcohol-based holographic recording materials have important properties and the monomeric composition of such materials has been optimized in terms of the energetic sensitivity and diffraction efficiency. High sensitivity has been obtained by adding a crosslinking agent, and gratings with a diffraction efficiency near 70% with energetic ex...

Ion this work we present a distortion of the usual H-D curve due to the action of a high contrast developer, Kodak D8 on ultra fine grain emulsion. This effect has been found for emulsions BB640, with a mean grain size of 20 nm. This anomalous curve shows two different linear zones for two different exposure ranges and no solarization region. Densi...

Renewed interest has been shown in the hybrid silver halide sensitized gelatin processes owing to the appearance of new photographic materials. In this study we show the possible compatibility between the models of latent image formation proposed prior to the existence of these new materials, bearing in mind that the refractive-index modulation and...

Ion this work we present a distortion of the usual H-D curve due to the action of a high contrast developer, Kodak D8 on ultra fine grain emulsion. This effect has been found for emulsions BB640, with a mean grain size of 20 nm. This anomalous curve shows two different linear zones for two different exposure ranges and no solarization region. Densi...

The variation in transmittance produced when a photopolymer is irradiated with a pulsed laser is analyzed and experimental results obtained when diffraction gratings are stored using pulsed exposure are presented. In either case, the influence of the energy of the irradiation pulse, the number of pulses, and the pulse repetition rate were studied....

We have developed a new polyvinylalcohol-based photopolymeric holographic recording material. The recording is obtained by the copolymerization of acrylamide and 2-hydroxiethylmethacrylate (HEMA). Diffraction efficiencies near 70% are obtained with exposures of ≈65mJ/cm2 in materials of 110-μm thickness. The addition of HEMA increases the thickness...

We describe a study of the free-radical homopolymerization kinetics for a system based on acrylamide, triethanolamine and methylene blue by analyzing temporal variations of the diffraction efficiency. The modulation index is related to the component’s parameters, giving as a result a method that can be used to determine the chain length of the poly...

In this paper we present the theoretical and experimental study of diffraction efficiency of unbleached holograms, showing that the volume fraction of metallic silver inside the gelatin after development (q) is the main parameter in the behavior of the holographic grating properties. Using this fact, and the obtained relationship between pH and q,...

In this paper we present the theoretical and experimental study of diffraction efficiency of unbleached holograms, showing that the volume fraction of metallic silver inside the gelatin after development (q) is the main parameter in the behavior of the holographic grating properties. Using this fact, and the obtained relationship between pH and q,...

The increase in the number of holographic applications used nowadays in different fields of science and engineering means that research is needed to develop improved materials for these applications. In this respect, important information can be obtained from the technologies and models developed with the pioneer materials, and this can be very use...

D-Log E curves, also known as H-D curves, are used since the XIX century as a tool for describing the characteristics of silver halide emulsions. This curve has a very standard shape, with a linear region, a toe, a shoulder and a solarization region. In this work we present a distortion of the usual curve due to the action of a high contrast develo...

The superadditivity effect in developers based on ascorbic acid with different organic redox systems was analyzed. A theoretical model was developed to qualitatively explain the properties of the components of developers and the mechanism of reduction of these processes so that the concentrations of the developers can be optimized. The developers w...

We present the results of the study as holographic recording material of a photopolymerizable mixture of polyvinyl alcohol and acrylamide, with a photoinitiator system formed by a 1:1 molar mixture of the anionic dye Rose Bengal (RB) and the cationic one Methylene Blue (MB), with triethanolamine as coinitiator. Under irradiation with 514 or 633 nm...

In this paper we present the experimental results obtained when diffraction gratings are stored using pulsed exposure in polyvinyl alcohol/acrylamide photopolymer deposited in a dry film. The influence of the energy of the irradiation pulse was studied and the number of pulses needed to reach maximum diffraction efficiency was obtained. The recordi...

We present theoretical results for angular responses of transmitted and diffracted beams in mixed amplitude–phase holographic gratings. Experimental results for gratings recorded in photographic emulsions and developed without a bleaching bath, with diffraction efficiencies of > 20 % , are also presented. The model shows an angular shift between mi...

In this paper we will analyse the behaviour of diffuse-object holograms recorded with the SHSG processing technique where the refractive-index modulation within the material will be the merit function to optimize the process. The behaviour of this merit function for several wavelengths will allow the understanding of the image formation mechanism f...

An ion pair (RBMB) isolated from Rose Bengal and Methylene Blue has been used as the photoinitiator in formulations of photopolymers tested as holographic recording materials in the form of dry films. Under irradiation with light of wavelength 633 or 514 nm, diffraction efficiencies of 65 and 35%, and sensitivities of 30 and 100 mJ cm(-2) have been...

An ion pair (RBMB) isolated from Rose Bengal and Methylene Blue has been used as the photoinitiator in formulations of photopolymers tested as holographic recording materials in the form of dry films. Under irradiation with light of wavelength 633 or 514 nm, diffraction efficiencies of 65 and 35%, and sensitivities of 30 and 100mJcm⁻² have been res...

We have demonstrated that holograms may be recorded in polyvinyl alcohol/acrylamide photopolymer dry films using pulsed laser exposure with a pulse length of 8 ns. We also studied the effect of the pulse fluency together with the number of pulses necessary to obtain maximum diffraction efficiency. The recording was performed using a holographic cop...

One of the main problems involved in the development of holography is that of the recording material used. In this study the behavior of a photopolymer is analyzed when thicknesses greater than 100μm are used. The photopolymer is made up of acrylamide as monomer, triethanolamine as radical generator, yellowish eosin as sensitizer and polyvinyl alco...