Table of contents

The 23rd Congress of the International Commission for Optics (ICO) was held in Santiago de Compostela (Spain) 26–29 August 2014, organized by the Universities of Vigo and Santiago de Compostela. Approximately 450 people attended the conference, sharing their knowledge in the cheerful, warm atmosphere of this lovely city. The conference was extremely successful in contributing to the mission of the ICO: to contribute worldwide, on an international basis, to the progress and diffusion of scientific and technological knowledge on optics and photonics.

Optics and photonics have reached a critical level of importance for the development of our societies and are present in a great many aspects of our technological progress, from communication systems supporting the Internet to the most modern techniques in medicine. Consistent with the conference slogan Enlightening the Future, the meeting stressed the importance of optical science as a key to technological progress in the coming years. UNESCO's designation of 2015 as the International Year of Light and Light-Based Technologies (www.light2015.org) acknowledges the importance of raising global awareness of how light and light-based technologies are present in a large fraction of today's advances and how they can address challenges in important areas such as energy, education, agriculture, and health.

The four-day conference highlighted eleven plenary talks by outstanding scientists working in important areas of optics and photonics. A. Aspect, T. Kippenberg (2013 ICO Prize awardee) and K. Razewski (2013 ICO Galileo Galilei Award) spoke on quantum optics; P. Russell and Yu. Kivshar lectured on topics related to optical processing devices as optical fibers and metamaterials for light shaping; N. X. Fang (2011 ICO Prize), U. Woggon, and A. Alú (2013 IUPAP Young Scientists Prize) discussed applications of optics to nanoscience; and K. Dholakia and J. Widjaja (2008 Galileo Galilei Award) presented in their plenaries applications of light to the tracking and manipulation of particles. Each day, in addition to plenary talks, nine or ten parallel sessions were held covering advances in both theory and applications of optics and photonics, ranging from quantum optics to technological applications. A total of 190 talks were given. Poster sessions allowed an additional 150 presentations. Congress participants came from every one of the five continents.

Included in the conference were three ceremonies for the granting of awards to plenary speakers noted above. Prizes awarded were the ICO Prize, the ICO Galileo Galilei Award, and the IUPAP young scientist Prize in Optics. Two additional prizes were awarded by OSA and SPIE to student's outstanding poster presentations.

Summaries of the presentations were available to Congress attendees. In addition, a call was made for submission of elaborated papers to be peer reviewed and published in the Journal of Physics: Conference Series. Conference papers were presented on applied optics, including color science and optomechanics (7 papers), optical imaging (7 papers), biophotonics (2 papers), optical metrology (4 papers), lasers and laser processing (5 papers), optoelectronics and optical communications (6 papers), nonlinear optics (5 papers), quantum optics (4 papers) and education and sustainability (4 papers). We would like to express our gratitude to the Bureau of the International Commission for Optics, the members of the organizing and scientific advisory committees, and to the University of Vigo and the University of Santiago de Compostela for their support and help in the organization of the Conference. We finally want to acknowledge all the authors that have submitted their work to be included in this number and very specially thank all those collaborating persons who acted as reviewers of the papers included in this number for their excellent (and often little recognized) work.

All papers published in this volume of Journal of Physics: Conference Series have been peer reviewed through processes administered by the proceedings Editors. Reviews were conducted by expert referees to the professional and scientific standards expected of a proceedings journal published by IOP Publishing.

Stiffness is the main reason to use SiC as a mirror substrate for aerospace applications. Also the SiC mechanical and thermal properties are superior to the optical material that is normally used for those applications. In this work, diamond tools and pastes were applied to obtain flat small diameter mirror substrates. The goals were to obtain flatness of λ/10 and Ra roughness of λ/100, for visible light.

Imaging optical systems components for satellites must have low specific mass and high stiffness, as weight is a problem for payloads and stiffness is essential to keep the substrate front surface shape. In this work, Re-carbonized Vitreous Carbon (RVC) was tested as a substrate material. The process to obtain RVC is different from the traditional process to obtain the Monolithic Vitreous Carbon (MVC). It is essential to understand the process to evaluate the surface roughness data. This work describes the process to obtain RVC, as a candidate for optical component substrate, and the results of its surface roughness measurements.

An automatic device for measuring the reflectance distribution from material surfaces was assembled in the laboratory. The mechanical setup employs two aluminum rotating arms driven by stepper motors: one for the light source and the second for the collecting optics. The two arms can rotate in the zenith direction from -90 to +90 degrees and the light collecting arm in the azimuth angle over 360 degrees, both with adjustable angular resolution. Measurements from black anodized aluminum, PTFE, graphite, porous silicon and a lambertian reference surface were performed to validate the system.

Currently there are a variety of techniques to determine the quality of optical surfaces, which must provide quantitative information of the deformation or the shape of the surface under test. This paper proposes to use the deflectometry technique using a Hartmann screen to test a spherical surface of the diameter and radius of curvature known. For this, the proposed experimental setup is presented, highlighting the importance of alignment and the measures distances, location between the screen and image capture system, measured from the center of curvature of the analyzed surface. Subsequently, by using these distances, the positions of the reflected rays and the positions of location of points on the screen, you can find the equation of the line associated with these two points and given this equation, we can deduce the value of the normal surface. With this result of normalsand using the general equation of deflectometry, we will obtain the shape of the surface under test.

In this paper we present a numerical analysis and experimental measurements of the temperature stabilization of high-power LED chips that we have obtained by employing an aluminum passive heat sink, designed to be used in a compact light bulb configuration. We demonstrate that our system keeps the temperature of the LED chip well-below 70° C yielding long-term operation of the device. Our simulations have been performed for a low-cost device ready to install in public streetlights. The experimental measurements performed in different configurations show a nice agreement with the numerical calculations.

This paper illustrates how to design a visual experiment to measure color differences in gonioapparent materials and how to assess the merits of different advanced color-difference formulas trying to predict the results of such experiment. Successful color-difference formulas are necessary for industrial quality control and artificial color-vision applications. A color- difference formula must be accurate under a wide variety of experimental conditions including the use of challenging materials like, for example, gonioapparent samples. Improving the experimental design in a previous paper [Melgosaet al., Optics Express 22, 3458-3467 (2014)], we have tested 11 advanced color-difference formulas from visual assessments performed by a panel of 11 observers with normal colorvision using a set of 56 nearly achromatic colorpairs of automotive gonioapparent samples. Best predictions of our experimental results were found for the AUDI2000 color-difference formula, followed by color-difference formulas based on the color appearance model CIECAM02. Parameters in the original weighting function for lightness in the AUDI2000 formula were optimized obtaining small improvements. However, a power function from results provided by the AUDI2000 formula considerably improved results, producing values close to the inter-observer variability in our visual experiment. Additional research is required to obtain a modified AUDI2000 color-difference formula significantly better than the current one.

The efficiency of the contour optical traps generated by the 4-channel liquid crystal modulator for the manipulation with both transparent and absorbing particles has been experimentally studied. The maximum velocity of the substrate movement at which the captured particle is kept in the optical trap was used for the traps efficiency estimation. The obtained data show the ability of the effective capture of transparent objects with the ring traps even in the course of the objects boundary (periphery) being under the impact. The possibilities of a smoothly control of the size and the form of optical traps for increasing of the capture efficiency have been demonstrated.

The brilliant iridescent colouring in male Morpho butterflies is due to the microstrutures and nanostructures present in the wing scales, rather than pigments. In this work Mueller matrix microscopy is used to investigate the polarization properties of butterfly wing scales in reflection and transmission. It is found that the top layer of more transparent scales (cover scales) have very different polarimetric properties from the ground iridescent scales. Images with high spatial resolution showing the retarding and diattenuating optical properties for both types of scales are provided.

In this paper, we describe a novel super resolution method for pinhole optics with variable pinholes array. The imaging system is based on super resolved time multiplexing method using variable or moving pinhole array. The improved resolution and signal to noise ratio are achieved with improved light intensity in the same exposure time, compared as in a single pinhole system. This new configuration preserves the advantages of pinhole optics while solving the resolution limitation problem and the long exposure time of such systems. The system can also be used as an addition to several existing optical systems with visible and invisible light as well as to x rays systems.

In this paper, the authors describe a novel technique for image nonlinearity and non-uniformity corrections in imaging systems based on gamma detectors. The limitation of the gamma detector prevents the producing of high quality images due to the radionuclide distribution. This problem causes nonlinearity and non-uniformity distortions in the obtained image. Many techniques have been developed to correct or compensate for these image artifacts using complex calibration processes. The presented method is based on the Papoulis - Gerchberg(PG) iterative algorithm and is obtained without need of detector calibration, tuning process or using any special test phantom.

The use of femtosecond laser radiation and super bright white LED in digital lensless holographic microscopy is presented. For the ultrafast laser radiation two different configurations of operation of the microscope are presented and the dissimilar performance of each one analyzed. The microscope operating with a super bright white light LED in combination with optical filters shows very competitive performance as it is compared with more expensive optical sources. The broadband emission of both radiation sources allows the multispectral imaging of biological samples to obtain spectral responses and/or full color images of the microscopic specimens; sections of the head of a Drosophila melanogaster fly are imaged in this contribution. The simple, solid, compact, lightweight, and reliable architecture of digital lensless holographic microscopy operating with broadband light sources to image biological specimens exhibiting micrometer-sized details is evaluated in the present contribution.

Light Sword Lens (LSL), i.e., an optical element with extended depth of focus (EDOF) characterized by angular modulation of the optical power in its conventional form is characterized by a linear relationship between the optical power and the angular coordinate of the corresponding angular lens sector. This dependence may be manipulated in function of the required design needs. In the present communicate this additional degree of freedom of design is used for elimination of the LSL shape discontinuity.

In this study, response of leaves of Chinese chives (Allium tuberosum) to ozone stress was investigated using functional optical coherence tomography (fOCT) based on biospeckle. The biospeckles arising out of dynamic motion of organelles can reflect the biological activities of plant. The fOCT biospeckle image was obtained by calculating the standard deviation (SD) of the fOCT temporal signal (biospeckle signal) at each and every point from the successively acquired OCT images. Plant leaves were subjected to treatment under different concentrations of O₃, and imaging data were acquired from back and front surfaces of the leaves. The internal cell structure within the Chinese chives leaves could be clearly visualized in the functional OCT biospeckle image, which was not clearly visible in conventional OCT cross-sectional image. The SDs were found to be increasing significantly, especially in the surface layers of both front and back sides of the leaf with ozone exposure. Thus, the fOCT based on biospeckle is found to be suitable for fast, non-destructive monitoring environmental stresses on plants, which can potentially lead to significant time saving, for which conventional techniques require a few days to a few weeks time.

We have tested the practical application of color measurements in the study of organic matter properties (C and N content, C/N ratios, degree of peat humification-DPH) of a 335 cm long peat core sampled at Tremoal do Pedrido bog. Usual and unusual CIELAB color parameters were measured on samples that were sectioned at high resolution (slices of 1 cm in thickness). The objective of the study is twofold: (i) describe a rapid, cost-effective and non-destructive method of assessing peat properties without the need of extractions and chemical methods and (ii) contribute to further research on applied colorimetry using the well-known CIELAB coordinates: L*, a*, b*, C*_ab and h_ab ('usual CIELAB color parameters') and the less well-known CIELAB parameters: [a* x b*], [a*/b*], [(a*/b*) x 1000], [1000 x a*/(L*+ b*)], [2000 x a*/(L* x b*)] and R_Lab= [a*(a*²+b*²)^1/2 10¹⁰]/(b* x L*⁶) ('unusual CIELAB color parameters'). Our findings show that L* and h_ab coordinates as well as [(a*/b*) x 1000], [2000 x a*/(L* x b*)] and R_Lab parameters give the best bivariate Spearman's correlations. Linear regression equations were calculated to predict peat properties from all CIELAB parameters under study and a notable fit (R²: 0.65-0.79) was obtained. The evaluation presented here indicates that the determination of usual and unusual CIELAB parameters offers potential for the study of peat organic matter properties and encourages the routine application of this methodology on other peat cores and organic soils.

In this work is presented in a simple manner, a method to generate null Ronchi gratings. This method consider the period of the Ronchi grating as a function of the x and y positions over the grating, compared to the currently known methods which utilize ray tracing or spot diagrams for the null Ronchi gratings calculus. We compare null Ronchi gratings reported in the literature against gratings calculated with our method. We have found that our method can calculate the Ronchi gratings for any conical surface in a satisfactory way.

In this work, the process to obtain the curve "Graylevel vs phase shift" of a transmissive spatial light modulator (SLM) HoloeyeLC2012 is described. This work arises from the need that exists for having a new optical surface testing method at INAOE's Optical Workshop. The SLM was placed in one arm of a Twyman-Green interferometer. The fringe shifts in the interference patterns were produced by displaying the different gray levels in the SLM. The gray level images displayed in the SLM were divided in two equal parts, the upper part was varying the different gray levels from 0 to 255 and the lower part stayed fixed with a gray level of 0 as reference. We show the different phase shifts and the experimental interferograms. From this analysis it was found out that a noticeable phase shift can be obtained from the 50 to the 190 gray levels.

Cross-bite, as a malocclusion effect, is defined as a transversal changing of the upper dental arch, in relation to the lower arch, and may be classified as skeletal, dental or functional. As a consequence, the expansion of maxilla is an effective clinical treatment used to correct transversal maxillary discrepancy. The maxillary expansion is an ancient method used in orthodontics, for the correction of the maxillary athresia with posterior crossbite, through the opening of the midpalatal suture (disjunction), using orthodontic- orthopaedic devices. Same controversial discussion arises among the clinicians, about the effects of each orthodontic devices as also about the technique to be employed. The objective of this study was to compare the strain field induced by two different orthodontic devices, named disjunctor with and without a connecting bar, in an acrylic model jaw, using fiber Bragg grating sensors to measure the strain patterns. The orthodontic device disjunctor with the bar, in general, transmits higher forces and strain to teeth and maxillae, than with the disjunctor without bar. It was verified that the strain patterns were not symmetric between the left and the right sides as also between the posterior and anterior regions of the maxillae. For the two devices is also found that in addition a displacement in the horizontal plane, particularly in posterior teeth, also occurs a rotation corresponding to a vestibularization of the posterior teeth and their alveolar processes.

A Michelson wavemeter was developed to test the accuracy and give traceability to the wavelength of external cavity diode lasers. These lasers were stabilized using a Littrow configuration and an iodine gas cell as frequency reference, and they were used as light sources in the assembly of a new interferometric system for the gauge block calibration. Previously, a microcontroller counting device with a Vernier logic and the uncertainty evaluation of the Michelson wavemeter had to be made.

The magnification and the Fresnel number determine the mode profile and losses in a bare unstable resonator. Upon inclusion of gain, both the beam pattern and the reflectivity are changed, more than in a stable cavity, because the counter-propagation intensities differ spatially and saturate the amplifier in a way that alters the mode profile, the reflectivity and the conditions of optimal operation. In this paper we present a numerical study of two types of cavities and compute the mode profile and losses in presence of an amplifier that saturates homogeneously. We compare these results with experimental data obtained on a TEA CO₂ laser.

In this work we analyze the conditions for the propagation of plane waves due to spontaneous oscillation within an active slab of width d and complex relative permittivity ε˜_b. The slab is immersed in transparent, semi-infinite media of relative permittivities ε_a and ε_c respectively, without external field sources -except, of course, the power source used for pumping the active medium in the slab. It is well known that, if there is enough gain in the active medium, it may sustain spontaneous oscillations of the electromagnetic field, which result in an impaired operation. This model gives a limiting value of the small signal gain to avoid this condition. It is applicable to disk lasers, amplifiers and other optoelectronic devices in which pumping is confined to a region with transverse dimensions much larger than its length.

This article presents the photo induced dehydrogenation of a cooled molecular jet of coronene, exposed to 266 nm laser radiation. Using unfocused laser radiation of 1064 nm, synchronously coupled with the ionization laser pulses, a system recently developed. Molecular beams were produced by laser desorption of coronene. Analysis of the photoproducts made by time-of flight mass spectrometer showed that a wide variety of ionic species were formed; more than 300 different species were observed. The results showed carbon clusters C⁺_n with n up to 24 as well as carbon/hydrogen clusters C⁺_nH⁺_x with masses higher than 300 m/z. The effect on the laser irradiance on the formation of different ions, in the rage from 10⁹ W/cm2 to 10¹⁰ W/cm2, is discussed as it is reflected on the evolution from the big ions to the smaller ones.

This paper presents the surface textured process of biometal Ti6Al4V by means of 355 nm Nd:YVO₄ nanosecond laser. Our target is to create structures with sizes which favour osseointegration. In this work a pattern of parallel grooves was generated after a deep analysis of the irradiation parameters involved. Ablation modifies not only the topography but also physico-chemical properties of the metal surface. Changes in the morphology and the physico-chemical state of the laser induced groove pattern were studied by a scanning electron microscopy, X-ray diffraction and X- ray photoelectron spectroscopy, which revealed, among others, an increase of micro roughness and a oxide layer entirely formed by TiO₂, which can improve biocompatibility properties of the textured surface.

We propose a laser-based method for fabricating microlens on borosilicate glass substrates. The technique is composed by a laser direct-write technique using a Nd : YVO₄ for fabricating the microlens arrays and a post thermal treatment with a CO₂ laser for improving its morphological and optical properties. The proposed technique will allow us to obtain microlenses with a broad range of diameters (50μm-500μm) and focal lengths (1mm-5mm). By combining laser direct-write and the thermal treatment assisted by a CO₂ laser, we are able to obtain good quality elements.

Azo-dye molecules may suffer from bleaching under certain illumination conditions. When this photoinduced process occurs, it generates an irreversible effect that is characterized by the loss of absorption of the dye molecule. Moreover, the well-known isomerization of azodye molecules does not occur anymore. In this work it is shown how the addition of a small amount of multi-walled carbon nanotubes (MWCNTs) helps to decrease the bleaching effect in a photosensitive guest-host azo-polymer film. Two different systems were fabricated using an epoxy resin as polymer matrix. An azo-dye, Disperse Orange 3, was used as photosensitive material in both systems and MWCNTs were added into one of them. The optical response of the polymeric systems was studied considering the degree of photoinduced birefringence. Photobleaching of the azo-dye was observed in all cases however, the effect is lower for the composite material containing 0.2 wt % MWCNTs. The weak interaction between MWCNTs and dye molecules is less favorable when the material is heated. The optical behavior of the heated composite material suggests that carbon nanotubes can be potentially used as azo dye dispensers. The results are interpreted in terms of the non-covalent interaction between azo-dye molecules and MWCNTs.

The exceptional properties of localised surface plasmons (LSPs), such as local field enhancement and confinement effects, resonant behavior, make them ideal candidates to control the emission of luminescent nanoparticles. In the present work, we investigated the LSP effect on the steady-state and time-resolved emission properties of quantum dots (QDs) by organizing the dots into self-assembled dendrite structures deposited on plasmonic nanostructures. Self-assembled structures consisting of water-soluble CdTe mono-size QDs, were developed on the surface of co-sputtered TiO₂ thin films doped with Au nanoparticles (NPs) annealed at different temperatures. Their steady-state fluorescence properties were probed by scanning the spatially resolved emission spectra and the energy transfer processes were investigated by the fluorescence lifetime imaging (FLIM) microscopy. Our results indicate that a resonant coupling between excitons confined in QDs and LSPs in Au NPs located beneath the self-assembled structure indeed takes place and results in (i) a shift of the ground state luminescence towards higher energies and onset of emission from excited states in QDs, and (ii) a decrease of the ground state exciton lifetime (fluorescence quenching).

We describe a terahertz time-domain spectrometer developed to perform measurements by reflection under a wide range of angles. The different parts of the device are described as well as the process of frequency-scale calibration and signal linearity evaluation. Also the main parameters that characterize the system and account their performance are measured. Finally an example of application to the measurement of the bandgap of a photonic crystal designed for the terahertz band is presented.

An interferometric characterization of the phase angular shifting produced by rotation of an ion-exchanged glass binary phase plates is presented. The inverse WKB method is used as a starting point to fabricate the phase plates, because such a method can only characterize the phase shift for normal incidence of the light on the plate. A complete phase angular shifting characterization is made by a Mach-Zehnder interferometer where a four-step phase shifting method is used for acquisition of data and a modified Carre algorithm is applied to data processing. The theoretical phase shifting is calculated by using the phase accumulated by a plane wavefront propagating in an axial graded-index media modelling an ion-exchanged glass phase plate. Experimental results present a good agreement with theoretical predictions.

In the present work a novel application of Transparent Boundary Conditions (TBC) to nematic liquid crystal cells (NLCC) with planar alignment and a patterned electrode is studied. This device is attracting great interest since it allows soliton steering by optically and externally induced waveguides. We employ the continuum Oseen-Frank theory to find the tilt and twist angle distributions in the cell under the one-constant approximation. The electric field distribution takes into account the whole 2D permittivity tensor for the transverse coordinates. Standard finite difference time domain methods together with an iterative method is applied to find an approximate solution to our coupled problem. A novel class of TBC is used to correctly define the boundary for both the distortion angle problem and the electric field distribution when using patterned electrodes. Thus, we achieve an important decrease of computational needs when solving this kind of problems and we are also capable of exploring weak anchoring conditions for NLCC.

Since few years ago, visible light communications (VLC) have experience an accelerated interest from a research point of view. The beginning of this decade has seen many improvements in VLC at an electronic level. High rates of transmission at low bit error ratios (BER) have been reported. A few numbers of start-ups have initiated activities to offer a variety of applications ranging from indoor geo-localization to internet, but in spite of these advancements, some other problems arise. Long-range transmissions mean a high BER which reduce the number of applications. In this sense, new redesigned optical collectors or in some cases, optical reflectors must be considered to ensure a low BER at higher distance transmissions. Here we also expose a preliminary design of a catadioptric and monolithical lens for a LI-FI receiver with two rotationally symmetrical main piecewise surfaces z_a and z_b. These surfaces are represented in a system of cylindrical coordinates with an anterior surface z_a with a central and refractive sector surrounded by a peripheral reflective sector and a back piecewise surface z_b with a central refractive sector and a reflective sector, both characterized as ideal for capturing light within large acceptance angles.

We show two different absolute distance measurement methods with micrometer accuracy based on frequency combs, and we discuss possible applications. Using a mode- locked laser and MEMS-based tracking optics, we measure the 3D position of a retroreflector within 10 ms and with a 24 μm volumetric accuracy. We also investigate modulator-based combs and show that they enable highly sensitive surface topography measurements with microsecond acquisition times and micrometer precision. Moreover, the potential for photonic integration of frequency comb sources is explored.

We investigate the modulational instability (MI) induced Supercontinuum generation (SCG) in exponential saturable nonlinearity. The pump power (P) is observed to behave in a unique way such that unlike the conventional Kerr case, the effective nonlinearity of saturable nonlinear system does not monotonously increases with an increase in power. The supercontinuum is observed at the shortest distance of propagation at power equal to the saturation power (P_s), whereas for all combinations of powers (P < P_s or P > P_s) spectral broadening occurs at longer distance.

We investigate the modulational instability (MI) of the optical beam propagating in the relaxing saturable nonlinear system. We identify and discuss the salient features of various functional forms of saturable nonlinear responses such as exponential, conventional and coupled type on the MI spectrum. Using Debye relaxation model, the relaxation of nonlinear response is effectively included along with the saturable nonlinear response (SNL). Using linear stability analysis, an explicit dispersion relation is determined for considering different functional forms of SNL. Firstly, we analyze the impact of SNL on the MI spectrum and found that the MI gain and bandwidth is maximum for exponential nonlinearity in comparison to other types of SNL's. Latter the relaxation of the nonlinearity is included, the inclusion of the finite value of the response time extends the range of the unstable frequencies literally down to infinite frequencies. In the regime of slow response, the MI inevitably suppressed regardless of the sign of the dispersion coefficient. To give insight into the MI phenomena, the maximum MI gain and the optimum modulation frequency is drawn as a function of the delay. Thus the MI dynamics in the system of relaxing saturable nonlinear media is emphasized and the significance of various functional forms of SNL are highlighted.

Polarization-dependent nonlinear transmissions are investigated by a pump-probe method in saturable-dye-doped films in which optically anisotropic saturable dyes are rigidly held with random orientations. The nonlinear transmissions measured by using uranine-doped poly(vinyl alcohol) films are compared with the theoretical predictions that are obtained by considering the effects of pump propagation and molecular orientation on the basis of a rate equation analysis for a four-energy-level model including an excited-state absorption. The measurements were conducted for the two cases of polarization states for which the polarization direction of the probe wave is either parallel or perpendicular to that of the pump wave; the experimental results considerably deviated from the theoretical ones for the probe wave perpendicularly polarized to the pump wave. It is shown that this is explained by modifying the energy level model to include the existence of a nearly-orthogonal component of the transition dipole moment associated with the ground-state absorption in uranine dyes.

Based in the numerical experiment techniques, we study the propagation dynamics of electromagnetic waves along one-dimensional array of parallel cylindrical subwavelength waveguides, possessing Kerr nonlinearity. By means of the proper selection of the array parameters, as well as the incident radiation properties and applying the Finite Difference Time Domain method, we are able to observe the light self-trapping in one single subwavelength waveguide. Furthermore, the position of the output beam can be controlled by the phase difference and the angle of incidence of the input beams. These results could give the possibility to control light by light, with perspectives in applications to implement integrated optics devices at nanoscale.

We present a new method for preparing multidimensional spatial qudits by means of a single phase-only spatial light modulator (SLM). This method improves previous ones that use two SLMs, one working in amplitude regime and the other in phase regime. To that end, we addressed diffraction gratings on the slits that define the state and then we performed a spatial filtering in the Fourier plane. The amplitude of the coefficients of the quantum state are determined by the modulation deep of the diffraction gratings, and the relative phase is the mean phase value of the diffraction gratings. This encoding result to be more compact, less expensive and use the photons more efficiently.

The generation and manipulation of entangled particles presents itself as one of the most important results in quantum mechanics. With the work from Bell, it was possible to prove the nonlocal nature of quantum mechanics, which is nowadays widely accepted. Apart from being possible to prove entanglement from Bell's inequality, it is difficult to compute the system as it increases the number of particles. Such a system containing N qubits can be described by Werner-Wolf-Zukowski-Brukner (WWZB) inequality. In this work, we show how to obtain the maximum of violation of WWZB inequality using a Werner state, simplifying the problem considerably. We get two different results; one for a system containing an odd number of particles and other for a system containing an even number.

Atomic clock transitions are desirable for quantum information storage and processing thanks to the protection from decoherence they provide. In the context of rare- earth-ion-doped crystals for quantum information storage, clock Zeeman or hyperfine transitions have been identified and exploited for long-lived storage in spin degrees of freedom. We present a theoretical and experimental analysis on the existence of an optical clock transition in Tm³⁺:YAG, in view of storage in optical coherences. The combination of a Zeeman-like term and a quadratic electronic Zeeman term in the Hamiltonian, lead to the existence of a magnetic field amplitude (12 mT) for which the derivative of the optical transition energy with respect to the field amplitude vanishes, regardless of the magnetic field orientation. We have verified this prediction through hole-burning spectroscopy experiments. In addition to that, a study of the behavior of the Hamiltonian as a function of the magnetic field orientation yields the direction for which both derivatives with respect to the magnetic field angular coordinates also vanish. The condition for an optical clock transition with three vanishing partial derivatives is met.

Here we present two different experimental techniques to generate atomic clouds in different density regimes that could be used as a tool to study Rydberg systems in different scenarios. As an example, we discuss an experiment in which the dynamics of Rydberg excitations were studied both in the few atom regime and in the high density regime.

Clinical Optometry lab training is devoted to develop the students skills needed in eye healthcare professional practice. Nevertheless, students always find difficulties in the management of some optometric instruments and in the understanding of the evaluation techniques. Moreover, teachers also have problems in explaining the eye evaluation tests or making demonstrations of instruments handling. In order to facilitate the learning process, webcams adapted to the optometric devices represent a helpful and useful tool. In this work we present the use of webcams in some of the most common clinical test in Optometry as ocular refraction, colour vision test, eye health evaluation with slip-lamp, retinoscopy, ophthalmoscopy and contact lens fitting. Our experience shows that with this simple approach we can do things easier: show the instrument handling to all the students at the same time; take pictures or videos of different eye health conditions or exploratory routines for posterior visualization with all the students; recreate visual experience of the patient during optometric exam; simulate colour vision pathologies; increase the interactions between students allowing them to help and correct each other; and also record the final routine exam in order to make possible its revision with the students.

The USC-OSA is a student chapter located at the University of Santiago de Compostela (Spain) whose objective is to bring optics and photonics knowledge closer to general public. In order to arouse kids' interest in Optics we developed an activity called Funny Light. This activity consisted on a visit of some USC-OSA members to a several local primary schools where we organized several optics experiments. In this work we present the optics demonstrations and the reaction of the 6 years-old students. The activities with greater acceptance include an explanation of light properties as polarization, refraction or reflection, and the workshop where they learnt how to build their own kaleidoscope and made a chromatic disk. Besides, they also participated in a demonstration and explanation of color properties and some optical illusions. We think that this activity has several benefits including spreading Optics through children meanwhile they have fun and experiment science in real life, as well as helping teachers to explain some complex properties and Physics phenomena of light. Given the broad acceptance of this activity, we are intending to make it a routine event of our student chapter repeating it every year.

The exploration process leading to the understanding of physical phenomena, such as light and its interaction with matter, raises great interest and curiosity in children. However, in most primary schools, children rarely have the opportunity to conduct science activities in which they can engage in an enquiry process even if by the action of the teacher. In this context, we have organised several in-service teacher training courses and carried out several pedagogic interventions in Portuguese primary schools, with the aim of promoting inquiry- based science education. This article describes one of those projects, developed with a class of the third grade, which explored the curricular topic "Light Experiments". Various activities were planned and implemented, during a total of ten hours spread over five lessons. The specific objectives of this paper are: to illustrate and analyse the teaching and learning process promoted in the classroom during the exploration of one of these lessons, and to assess children's learning three weeks after the lessons. The results suggest that children made significant learning which persisted. We conclude discussing some processes that stimulated children' learning, including the importance of teacher questioning in scaffolding children's learning and some didactic implications for teacher training.

In this paper, performance monitoring program is applied to a grid-connected high concentration photovoltaic power plant in order to identify any operational problem and to make sure of its optimal and continuous power generation working conditions. A preventive maintenance plan was also established and proposed for the whole system.