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Electromagnetic fields carry a linear and an angular momentum, the first being responsible for the existence of the radiation pressure and the second for the transfer of torque from electromagnetic radiation to matter. The angular momentum is considered to have two components, one due to the polarization state of the field, usually called Spin Angular Momentum (SAM), and one due to existence of topological azimuthal charges in the field phase profile, which leads to the Orbital Angular Momentum (OAM). For non-paraxial fields these two contributions are not independent of each other, something which is described as spin-orbit coupling. It has been recently proved that electromagnetic fields necessarily carry also invariant radial charges that, as discussed in this work, play a key role in the angular momentum. Here we show that the total angular momentum consists in fact of three components: one component only dependent on the spin of the field, another dependent on the azimuthal charges carried by the field and a third component dependent on the spin and the radial charges contained in the field. By properly controlling the number and coupling among these radial charges it is possible to design electromagnetic fields with a desired total angular momentum. In this way it is also possible to discover fields with no orbital angular momentum and a spin angular momentum typical of spin-3/2 objects, irrespective of the fact that photons are spin-1 particles. [ABSTRACT FROM AUTHOR]

We propose a novel approach, "faFJP", to the computer controlled polishing (CCP) of mini aspheres down to 0:2 mm. The generation of locallytunable, full-aperture footprints is accomplished by applying a Fluid Jet Polishing (FJP) beam larger than the full aperture being polished and varying the incident angle. [ABSTRACT FROM AUTHOR]

A new software tool, called PanDao, for optical system designers is presented enabling during the design stage a simulation of the optimum fabrication chain and technologies needed as well as a fabrication cost impact analysis of design parameters and tolerances. [ABSTRACT FROM AUTHOR]

Since the electron is the photon-generator and the electron is rotating around itself and around the nucleus, the emitted photon from the electron should have the effect of these rotating motions. So, the photon has a three-dimensional motion, including a transition movement and a rotary motion. And it traverses in a helical trajectory. By using this definition, we have proved wave-particle duality at the same time and introduce a new equation for the photon motion and its energy. [ABSTRACT FROM AUTHOR]

The optical quality of three multifocal intraocular lenses (MIOLs) was measured in vitro using the area under the modulation transfer function (MTFa) and energy efficiency (EE). We evaluated those metrics through-focus (TF) by axially scanning the image space with three wavelengths (R, G, B). High linear correlation between MTFa and EE was found for all cases. Correlations between optical in vitro results (polychromatic TF-MTFa and TF-EE) and clinical visual acuity (VA) defocus curves for the three MIOLs allowed us to derive mathematical expressions. Both metrics proved to be equivalent to predict postoperative VA. [ABSTRACT FROM AUTHOR]

We present a simple, high-duty-cycle, cavity-enhanced optical absorption measurement technique based on delay-limited Pound-Drever-Hall (PDH) sideband locking. The chosen circuit naturally provides realtime readout of the amplitude quadrature of the PDH error signal, which can be mapped onto the cavity's internal loss rate while using the phase quadrature to lock sideband frequency to the cavity mode. Our proofof-concept device comprises a 5-cm-long Fabry-Perot cavity with a 450 kHz bandwidth (finesse 6800, 350 ns power ringdown), and a feedback bandwidth of several MHz, limited primarily by the group delay of our electronics. This technique could readily be applied to other optical resonators such as fiber cavities, with potential applications in radiation dosimetry. [ABSTRACT FROM AUTHOR]

We study switching operation in a plasmonic coupler using fs-pulses. Simulations using the finite difference time-domain method (FDTD) are carried out showing how the output changes as the pulse energy increases raising from zero to a maximum. Both cases of neglecting and realistic losses are considered in order to compare. The work is intended to explore the use of pulses for all-optical signal processing in a potentially interesting system for integrated photonics at the nanometric scale. [ABSTRACT FROM AUTHOR]

We demonstrate a novel approach to the determination of optical loss coefficients in metal-coated fibers in a 0.4-1.9 μm wavelength range. It is based on measuring the change of temperature-dependent electrical resistance of the metal coating caused by laser radiation transmitted through the fiber. A number of single-mode and multimode metallized fibers were investigated using several laser sources operating in visible and near infrared ranges. The spectral dependencies of optical losses of copper-coated fibers were experimentally obtained. The region that corresponds to the minimum optical losses is located near 1 μm wavelength. The increase of radiation losses in 1.5-1.9 μm region is much steeper compared to polymer-coated fibers. [ABSTRACT FROM AUTHOR]

The nonlinear electrical response from a low temperature grown GaAs photomixer driven with the optical beat of two continuous-wave lasers allows frequency mixing between radiofrequency and THz-waves. Phase-sensitive demodulation of the signal from a modulated THz-wave is theoretically and experimentally demonstrated using a photomixer electrically driven with an alternative voltage at the modulation frequency. [ABSTRACT FROM AUTHOR]

We present the optical simulation and design concept of a spatial heterodyne spectrometer (SHS) for mobile applications. A framework using Python and Zemax OpticStudio was developed for the optical system design and automated tolerance analysis from the incoming light, the spectrometer and the imaging lens system to the 2D detector. The spectrometer design and the fabrication methods were validated using a test setup in the VIS spectral range for a future SHS fabrication in the LWIR spectral band operating on small unmanned aerial vehicles (SUAV) for remote sensing applications. [ABSTRACT FROM AUTHOR]

Binocular and accommodative dysfunctions affect the efficiency and coordination of the eyes, and this may impair reading performance. Reading can be evaluated using accuracy and speed measures. In this study, we searched for evidence that dysfunctions of accommodation (i.e. accommodation insufficiency, IA) and binocular vision (i.e. convergence insufficiency, CI) and also hyperopia have impact on reading ability. A sample of 292 children read a text following vision screening. The sample was composed of control children and children with the conditions: AI; CI and hyperopia. Multilinear regression analysis was used to evaluate the influence of variables sex, age and visual condition (control, AI, CI and hyperopia) on reading accuracy and speed. The results showed that ~7% of the variation in reading accuracy was explained by a model where age (p=0.001), and presence of AI (p<0.001) and hyperopia (p=0.019) were statistically significant. On the other hand, ~38% of the variation in the index of speed was explained by age alone (p<0.001). These results confirm the importance of age on children's ability to read, and suggests that AI and hyperopia, but not CI may affect reading accuracy. Reading speed does not appear to be affected by the presence of binocular or accommodative dysfunction. [ABSTRACT FROM AUTHOR]

A slit-scanning tomography system previously developed in the Centre of Physics of University of Minho allows to capture images of the eye and posteriorly calculus of the biometric (thickness and curvature) and optical (wavefront aberrations) properties of the corneal and crystalline lens surfaces. It is intended to optimise the system for an accurate computing of these properties of the crystalline lens in the relaxed state and during ocular accommodation. In this study, preliminary experimental results of the crystalline lens imaging of a subject during accommodation are presented. [ABSTRACT FROM AUTHOR]

Three-dimensional laser writing inside silicon remains today inaccessible with the shortest infrared light pulses unless complex schemes are used to circumvent screening propagation nonlinearities. Here, we explore a new approach irradiating silicon with trains of femtosecond laser pulses at repetition rates up to 5.6 THz. This extremely high repetition rate is faster than laser energy dissipation from microvolume inside silicon, thus enabling unique capabilities for pulse-to-pulse accumulation of free carriers generated by nonlinear ionization, as well as progressive thermal bandgap closure before any diffusion process comes into play. By space-resolved measurements of energy delivery inside silicon, we evidence a net increase on the level of space-time energy localization. The improvement is also supported by experiments demonstrating an apparent decrease of the energy threshold for modification and drastic improvements on the repeatability, uniformity, and symmetricity of the produced features. The unique benefits of THz bursts can provide a new route to meet the challenge of 3D inscription inside narrow bandgap materials. [ABSTRACT FROM AUTHOR]

A method based on multiple Fiber Bragg Gratings (FBG) and a structure fabricated using a 3D printer for diameter measurement is proposed and experimentally demonstrated. The sensor is easily developed inserting the FBG on the structure and fixing the FBG in two points. Due to this arrangement, when the diameter is reduced a force is applied on the sensor and this causes a wavelength shift. The study is divided in two steps using one experimental setup. At first, each FBG response is independently evaluated concerning the diameter variation and after that, the FBGs are evaluated together. The results demonstrated that the structure can be used as a way to monitor the diameter variation in some applications. [ABSTRACT FROM AUTHOR]

The most adverse weather condition for road safety happens when there is water, snow, or ice on the road surface because their presence highly decreases friction. Therefore, it is essential to drain or repel them quickly. If the water drops are repelled from the surface or the ice/snow formation is avoided with the application of superhydrophobic coatings, roads become safer. In order to functionalize the asphalt mixtures used in road pavements, nano/micromaterials, such as Polytetrafluoroethylene (PTFE), TiO2, and SiO2, among others have been applied by spraying coating. The mixes are usually characterized by the water contact angle, and the surface roughness is typically assessed by optical and electron analysis. This research work aims to present a brief overview of superhydrophobic asphalt mixtures. [ABSTRACT FROM AUTHOR]

The investigation of a D-shaped photonic crystal fiber sensor with a bimetallic layer for operation at the visible and infrared spectra is presented. The bimetallic layer is composed by silver and gold slabs deposited adjacently on the flat face of the fiber. It is shown that this architecture allows the excitation of two sharply distinguished plasmon resonance, which suggest potential applications for multiparameter sensing. [ABSTRACT FROM AUTHOR]

Photothermal therapy is a developing therapeutic technic mainly regarding the usage of nanoparticles considering their proneness to assemble around malignant tissue and induce their destruction by converting electromagnetic radiation into thermal radiation. In order to optimize this process, controlling the area of incidence in a way that it can fit the tumour and prevent damage of healthy cells is of great importance. This study was conducted by designing an optical system based on zoom systems for manipulating an initial input beam and adjust it to the most common skin cancer sizes. Two solutions are proposed, accomplishing spot sizes at 150 mm from the last lens within the approximate range of 2 mm to 76 mm, with beam divergences lower than 3 mrad. [ABSTRACT FROM AUTHOR]

In this work, a long-period fiber grating (LPG) based sensor was evaluated as a sensing device for micro-force measurement, in the order of micro Newtons. It was used an LPG fabricated by arc-inducted technique in a SMF-28 standard optical fiber. The optical fiber was fixed between two clamps with a separation of 150 mm with the middle of the LPG located at the center. Characterizations were performed in terms of temperature, curvature and strain. The grating was then used as a micro-force sensor by means of both curvature and strain, induced by a hung mass in a stretched fiber. Furthermore, the evaluation of a precurvature LPG was performed to assess if an increase of sensitivity is achieved. Micro-force sensitivity achieved with the stretched LPG was 1.41 nm/mN and it was demonstrated that its sensitivity can be enhanced to 5.14 nm/mN with a pre-curvature of 2.2 m–1 applied to the LPG, achieving a spectral resolution of at least 15.6 μN. [ABSTRACT FROM AUTHOR]

Highlighted are the linear extreme dynamic range calibrated target imaging tests of the CAOS smart camera showing a 177 dB linear dynamic range operation with an optical attenuation controlled bright laser target [ABSTRACT FROM AUTHOR]

Experimentally highlighted are the limitations & optimizations of the CMOS sensor-mode engaged for the CAOS smart camera. Demonstrated is an optimized method for finding the Camera Response Function (CRF) using a calibrated target. [ABSTRACT FROM AUTHOR]

An approach based on the finite-difference time-domain (FDTD) method is developed for simulating the dynamics of two ultrashort laser pulses inside a saturable absorbing media. This work discusses the results obtained using this numerical model for the prediction of the nonlinear absorbing media behaviour as well as how it affects the final double pulse combination. These results can be used to improve contrast cleaning conditions for high power laser chains and for synchronization studies, this last application was checked in the VEGA facility lab as a code validation. [ABSTRACT FROM AUTHOR]

We present our investigation on the crystallization of IBS HfO2 on (0001) SiO2. The crystallization was studied by in-situ XRD. The activation energy was 2.6±0.5 eV. The growth follows a two-dimensional mode. LIDT measurements (5000-on-1) with 10 ns pulses at 355 nm on 3QWT HfO2 layers shows that the crystallization leads to increase of the laser irradiation resistance. The 0%-LIDT of the as coated sample was 3.1 J/cm2 and increased to 3.7 J/cm2 after 5h @ 500°C. [ABSTRACT FROM AUTHOR]

We demonstrate the integration of arrayed waveguide grating (AWG) de-multiplexer with a low loss and low index contrast platform, i.e., a striped-loaded slot waveguide (SLWG). The SLSW-AWG is designed to operate around the wavelength λ = 1550 nm with a four-output channel. The device experiences excellent output parameters: channel width δλ = 1.39 nm at -3dB, channel spacing Δλ = 2.43 nm and extinction ratio ER = 9.87 dB, useful for sensing applications. [ABSTRACT FROM AUTHOR]

In this work, methods and procedures are investigated for the holistic simulation of the dynamicalthermal behavior of high-performance optics like lithography objectives. Flexible multibody systems in combination with model order reduction methods, finite element thermal analysis and optical system analyses are used for transient simulations of the dynamical-thermal behavior of optical systems at low computational cost. [ABSTRACT FROM AUTHOR]

We experimentally demonstrate the generation of temporal pulse doublets from the propagation of initial super-Gaussian waveforms in an optical fiber with anomalous dispersion. The nonlinear focusing dynamics leads to picosecond structures that are characterized both in amplitude and phase. Their close-to-Gaussian Fourier-transform limited shape is found in excellent agreement with numerical simulations. This single-stage reshaping scheme is energy efficient, can sustain GHz repetition rates and temporal compression factors around 10 are demonstrated. [ABSTRACT FROM AUTHOR]

In this work we show that a silicon optomechanical crystal cavity can be used as an optomechanical oscillator when driven to the phonon lasing condition with a blue-detuned laser. The optomechanical cavity is designed to have a breathing like mode vibrating at Ωm/2π =3.897 GHz in a full phononic bandgap. Our measurements show that the first harmonic displays a phase noise of -100 dBc/Hz at 100 kHz. Stronger bluedetuned driving leads eventually to the formation of an optomechanical frequency comb, with lines spaced by the mechanical frequency. The measured phase noise grows up with the harmonic number, as in classical harmonic mixing. We present real-time measurements of the comb waveform and show that it can be adjusted to a theoretical model recently presented. Our results suggest that silicon optomechanical cavities can play a role in integrated microwave photonics. [ABSTRACT FROM AUTHOR]

We study the impact of temporal randomness on the formation of vectorial dispersive shock-waves that emerge due to the interaction of a partially coherent probe wave co-propagating together with an orthogonally polarized intense short pulse. Experiments carried out in a normally dispersive optical fiber demonstrate that the lack of coherence of the probe landscape acts as a strong diffusive term, which is able to hamper or inhibit the vectorial shock formation. [ABSTRACT FROM AUTHOR]

We numerically study the temporal patterns that emerge upon the propagation of one or two π phase jumps in a nonlinear optical fiber. Both normal and anomalous regimes of dispersion are considered. The analytical derivation of linear patterns based on Fresnel's integrals provides some clues to better understand the properties of the resulting coherent structures. [ABSTRACT FROM AUTHOR]