Subwavelength Bessel beams in wire media

Recent progress is emerging on nondiffracting subwavelength fields propagating in complex plasmonic nanostructures. In this paper, we present a thorough discussion on diffraction-free localized solutions of Maxwell’s equations in a periodic structure composed of nanowires. This self-focusing mechanism differs from others previously reported, which lie on regimes with ultraflat spatial dispersion. By means of the Maxwell–Garnett model, we provide a general analytical expression of the electromagnetic fields that can propagate along the direction of the cylinder’s axis, keeping its transverse waveform unaltered. Numerical simulations based on the finite element method support our analytical approach. In particular, moderate filling fractions of the metallic composite lead to nonresonant-plasmonic spots of light propagating with a size that remains far below the limit of diffraction.This research was funded by the Spanish Ministry of Economy and Competitiveness under the project TEC2011-29120-C05-01

Dyakonov surface waves in lossy metamaterials

We analyze the existence of localized waves in the vicinities of the interface between two dielectrics, provided one of them is uniaxial and lossy. We found two families of surface waves, one of them approaching the well-known Dyakonov surface waves (DSWs). In addition, a new family of wave fields exists which are tightly bound to the interface. Although its appearance is clearly associated with the dissipative character of the anisotropic material, the characteristic propagation length of such surface waves might surpass the working wavelength by nearly two orders of magnitude.This research was funded by the Spanish Ministry of Economy and Competitiveness under the Project TEC2013-50416-EXP

Analysis and comparison of monofocal, extended depth of focus and trifocal intraocular lens profiles

To test the feasibility of using profilometers to extract information about IOL surfaces design. A standard monofocal IOL (Tecnis 1), a monofocal IOL that provided some depth of focus (Eyhance), an extended depth of focus IOL based on refractive optics (Mini Well) and a trifocal IOL based on diffractive optics were used in this study (Tecnis Synergy). The surface topography of the IOLs was measured by using a multimode optical profilometer. Posterior surface of Tecnis 1 IOL was spherical and the anterior surface aspherical. In the Eyhance IOL, posterior surface was spherical and anterior surface did not fit to any of our reference surfaces, indicating a higher order aspheric surface design. In the Mini Well Ready IOL, a best-fit sphere surface was obtained for the second surface and a high order aspherical surface design was deduced for the first surface. The anterior surface of the Synergy IOL was aspherical and the base curve of the diffractive structure fitted very well to a spherical surface. To consider an aspheric surface as possible best-fit surface provided more information than if only best-fit spherical surface was considered. The high order aspheric surface designs employed in the IOLs studied presented differences, regarding best-fit asphere surface, higher than 1 micron. These differences were correlated with the generation of spherical aberration complex profiles (with Zernike terms higher than 4th order) and with the production of distinct amounts of depth of focus. This method was also useful to deduce the base curve of diffractive surfaces.This work was supported by the “Generalitat Valenciana” of Spain (project AICO/2021/130)

Ultrathin high-index metasurfaces for shaping focused beams

The volume size of a converging wave, which plays a relevant role in image resolution, is governed by the wavelength of the radiation and the numerical aperture (NA) of the wavefront. We designed an ultrathin (λ/8 width) curved metasurface that is able to transform a focused field into a high-NA optical architecture, thus boosting the transverse and (mainly) on-axis resolution. The elements of the metasurface are metal-insulator subwavelength gratings exhibiting extreme anisotropy with ultrahigh index of refraction for TM polarization. Our results can be applied to nanolithography and optical microscopy.Spanish Ministry of Economy and Competitiveness (MEC) (TEC2013-50416-EXP)

Substantial enlargement of angular existence range for Dyakonov-like surface waves at semi-infinite metal-dielectric superlattice

We investigated surface waves guided by the boundary of a semi-infinite layered metal-dielectric nanostructure cut normally to the layers and a semi-infinite dielectric material. Using the Floquet-Bloch formalism, we found that Dyakonov-like surface waves with hybrid polarization can propagate in dramatically enhanced angular range compared to conventional birefringent materials. Our numerical simulations for an Ag-GaAs stack in contact with glass show a low to moderate influence of losses.This research was funded by the Qatar National Research Fund under the project NPRP 09-462-1-074, by the Spanish Ministry of Economy and Competitiveness under the project TEC2009-11635, and by the Serbian Ministry of Education and Science under the projects III 45016 and TR 32008

Complete algorithm for the calculation light patterns inside the ocular media

Realistic mathematical models are of great importance for studying the optical performance of the human eye. Light propagation algorithms provide robust methods to calculate field distributions inside a homogeneous medium, and thus they can be applied to the study of light patterns inside the anterior and posterior chambers of the eye. Dealing with real eyes implies using very short propagation distances together with highly refractive power surfaces. Thus, the general solutions of the field equation are used instead of paraxial Fresnel solutions. Conditions of application and sampling conditions of the method are clearly stated here. Numerical evaluation of the different refractive surfaces is also analysed. The main result is that a complete algorithm to obtain light patterns at any axial distance inside the eye is proposed. The method uses real corneal measures and axial distances together with crystalline models. Statistical results and individual predictions show the validity of the model. Application of the method is illustrated with the study of a bifocal intraocular lens.This work has been partially supported by the Conselleria de Cultura, Educació i Esport of the Generalitat Valenciana, through project GV04A/578

Preliminary study on the use of near infrared hyperspectral imaging for quantitation and localisation of total glucosinolates in freeze-dried broccoli

peer-reviewedThe use of hyperspectral imaging to (a) quantify and (b) localise total glucosinolates in florets of a single broccoli species has been examined. Two different spectral regions (vis–NIR and NIR), a number of spectral pre-treatments and different mask development strategies were studied to develop the quantitative models. These models were then applied to freeze-dried slices of broccoli to identify regions within individual florets which were rich in glucosinolates. The procedure demonstrates potential for the quantitative screening and localisation of total glucosinolates in broccoli using the 950–1650 nm wavelength range. These compounds were mainly located in the external part of florets.Universidad de SevillaJ.M. Hernández-Hierro thanks the Spanish MICINN for the Juan de la Cierva contract (JCI-2011-09201) and Universidad de Sevilla for the mobility Grant (Universidad de Sevilla Research Plan). Spanish MICINN Project AGL2011-30254-C02 and Junta de Andalucia PGC Project AGR 6331

Determinación de la aberración cromática longitudinal en ojos humanos

En este trabajo, el Grupo de Óptica y Ciencias de la Visión de la Universidad de Alicante muestra los últimos resultados obtenidos en su línea de trabajo. Los autores calculan la aberración cromática longitudinal mediante el cálculo de patrones de luz propagados a través del ojo encontrando dichas distribuciones, tanto en amplitud como en fase, en un plano cualquiera del interior del ojo humano del cual se conocen su topografía corneal y sus medidas biométricas. Se ha modelado la dependencia de todos los medios oculares con la longitud de onda siguiendo la ecuación de Cauchy. Los autores han realizado el estudio de diez sujetos y han comparado los resultados con medidas reales de aberración cromática, mostrando la concordancia del cálculo numérico. Como muestra de la capacidad de la técnica utilizada, se ha aplicado el método al estudio de la aberración cromática de un queratocono.In this communication the authors have determined the longitudinal chromatic aberration using an algorithm for free space propagated pattern calculation. From topographical and biometric data, the algorithm is capable of provide amplitude and phase distribution of the field at any distance inside the eye. The wavelength dependence of all ocular media has been modelled through the Cauchy formula. Results from the study of ten subjects are compared with real measures of the chromatic aberration, showing a good agreement with numerical calculations. The capabilities of the technique have been demonstrated by applying the method to the study of the chromatic aberration of a keratoconus.Este trabajo ha sido financiado por la Conselleria de Cultura, Educació i Esport de la Generalitat Valenciana, a través del proyecto GV04A/578

IV Edición. Colaboración con centros de secundaria para la formación experimental de alumnos de bachillerato

La “Red para la colaboración con centros de secundaria para la formación experimental de alumnos de bachillerato” ha llevado a cabo este año su quinta edición. La línea de actuación prioritaria se mantiene siendo el fomento del intercambio de experiencias en diferentes campos del conocimiento científico dirigidas al alumnado que cursa Bachillerato o estudios de Secundaria. En la edición de este curso hemos recibido en nuestros laboratorios a 233 alumnos procedentes de 11 centros de la provincia de Alicante para la realización de diferentes prácticas. El periodo elegido, como viene siendo habitual han sido los meses de Enero y Febrero, durante el periodo de elaboración de exámenes, no lectivo que tiene la Universidad de Alicante para los alumnos de todas las titulaciones de grado. en las que los alumnos han sido los verdaderos protagonistas. Esto significaría que en las 5 ediciones de nuestra red hemos recibido en nuestros laboratorios en total a 858 alumnos de Bachiller y de de 4º año de educación secundaria obligatoria (ESO). Estudiantes que han realizado bajo nuestra supervisión las prácticas de laboratorio que previamente habían sido ofertadas a sus centros. En todas las ediciones, los resultados obtenidos han sido plenamente satisfactorios tanto para los alumnos como para todos los profesores integrantes de la Red. Pensamos que es tiempo de reunir y reflexionar sobre todo el trabajo realizado

Understanding the Real Effect of the High-Order Aberrations after Myopic Femto-Lasik

In this work we try to understand the real effect of increase in aberrations after Femto-LASIK surgery on the patient’s final visual quality, specifically when the visual acuity measurement is considered. A clinical study with 37 eyes of 20 patients that underwent myopic Femto-LASIK surgery and different personalized eye model simulations were carried out. In clinical study, correlations between pre- and postoperative parameters with visual acuity were analysed. Eye simulations (based on real data) provided simulations of vision quality before and after surgery. Our main results showed a significant increase in aberrations was obtained after surgery; however, no differences were found between the preoperative corrected distance visual acuity (CDVA) and the postoperative uncorrected distance visual acuity (UDVA). This absence of differences in visual quality could be explained by performing different simulations on three eyes that would cover most of the possible clinical situations. Simulations were implemented considering a pupil size of 2.5 mm and the personalized data of each patient. Results showed that final visual acuity (VA) change are determined by the final high-order aberrations (HOAS) and their increase after surgery but measured under photopic conditions. In conclusion, customized analysis of higher-order aberrations in scotopic pupils better predicts patient visual acuity after Lasik surgery.This work was supported by the “Generalitat Valenciana” of Spain (project AICO/2021/130)