A project-based teaching course for postgraduate students in the field of Photonics Engineering is based on the implementation of a Spectrophotometer. Hard and soft skills are evaluated in the implementation with an auto-evaluation criteria.
In this work, a novel method to obtain all-dielectric toroidal response metasurfaces in the W-band and THz range is demonstrated. Two designs are proposed, a symmetric and asymmetric disk metasurface. The first design is intended to corroborate the theoretical analysis, demonstrating the excitation of a strong toroidal mode resonance at 93.2 GHz. Then, the second design is used to demonstrate that symmetry-breaking variations in the disk dimensions, could lead to birefringent metasurfaces, affecting the polarization of the impinging light. Two structures are designed, a polarization beam splitter and a polarization converter. Such devices are difficult to obtain at the target frequency range with low absorption, so they could be of particular interest for the next generation of 5G communications and THz devices.
A free-space laser communication system has been designed and partially developed as an alternative to standard RF
links from UAV to ground stations. This project belongs to the SINTONIA program (acronym in Spanish for low
environmental-impact unmanned systems), led by BR&TE (Boeing Research and Technology Europe) with the purpose
of boosting Spanish UAV technology.
A MEMS-based modulating retroreflector has been proposed as a communication terminal onboard the UAV, allowing
both the laser transmitter and the acquisition, tracking and pointing subsystems to be eliminated. This results in an
important reduction of power, size and weight, moving the burden to the ground station. In the ground station, the ATP
subsystem is based on a GPS-aided two-axis gimbal for tracking and coarse pointing, and a fast steering mirror for fine
pointing. A beacon-based system has been designed, taking advantage of the retroreflector optical principle, in order to
determine the position of the UAV in real-time. The system manages the laser power in an optimal way, based on a
distance-dependent beam-divergence control and by creating two different optical paths within the same physical path
using different states of polarization.
New all-plastic electrochromic devices have been manufactured using commercial PEDOT foils and classical polymer electrolyte electrodeposition techniques. Several devices with different areas have been electrically characterized by using an impedance spectroscopy technique. After a brief description of the manufacturing process, we discuss electrical properties with the size of the device. Real and imaginary parts of the impedance have been plotted as a function of frequency. Some interesting conclusions have been derived from those plots, and some improvements in manufacturing process of this kind of devices are also proposed.
Electrochromic (EC) materials are used mainly for domotic applications, such as transparency controlled windows or rear-view mirrors in cars. The device construction is a sandwich of electrochemical compounds, which change their optical properties when applying voltage. Although the changes that are used in the applications take place in the visible, there are also changes in the near infrared region. In the last years, some works have proposed their use in fiber optic applications, mainly as optical modulators or VOAs (Variable Optical Attenuator). EC devices have usually slow responses (several seconds) and low transmittance range, specially the organic ones. The slow response is the major drawback for their use as modulators. But in NIR transmittance ranges, there are promising results in materials like ruthenium or PEDOT (poly(3,4-ethylenedioxythiophene)). In this work, we will study the possible use in VOAs of new EC devices developed with the minimum number of layers, by their response in telecommunications wavelengths. These devices are manufactured in such a way that the integration in fiber optic devices is an easy task. The minimum number of layers and the easy construction are improvements over the existing possibilities. PEDOT is the EC material on these devices, and different manufacturing ways are compared in order to detect the best possible candidate to use.
The control of transmittance and its use in glazing have powered the research on electrochromic devices in the last decade. The search for new materials to be used in different applications is a goal today. We characterize new electrochromic devices following an all-plastic construction. Poly(ethylendioxy-tiophene) (PEDOT) is used between plastic substrates and sandwiched symmetrically with a poly(ethylene oxide)-based polymer electrolyte. This multilayer acts as an electrochromic device without the necessity for an ITO layer. Several devices are tested to determine their electro-optical characteristics using cyclic voltammetry and complex impedance spectroscopy techniques, among others. Additionally, a protocol of electrical and optical characterization is proposed. The devices switch between 0 and 3 V with no dependence on the electric field direction, due to their layer construction symmetry. Impedance and voltammetry measurements show a hysteretic behavior from which charge injection can be derived. Finally, transmittance changes above 14% are measured at a 600-nm wavelength, so that further research must be done in materials and sticking process to improve the contrast. Bleaching and coloring times of 20 to 30 s make these devices potential candidates for applications in domotics, environment control or vision, and color filters.
Santiago Mar Sardana, Fernando Munoz, Juan-Carlos Gonzalez, Angel de Frutos, Marco Gigosos Perez, M. Inmac De La Rosa Garcia, Maria Perez, Carlos Baladron, Juan Aparicio-Calzada, Juan del Val, Manuel Gonzalez-Delgado, Luis Fuentes, Victor Gonzalez, Andres Bustillo, Ana Gonzalo, Raul Pastor, Maria Gonzalez, Alberto Barbes, Raul Garcia, Anabel Manchon, Ricardo Vergaz, Prudencio Herrero, Maria Martin, Ramon Margarida, Alberto Berjon
In this article we present the different groups of investigation which work at the Department of Optics and Applied Physics of the University of Valladolid (Spain). The areas covered by these groups are the following: (1) optical diagnostic techniques in plasmas, (2) calculation of spectral line shapes, (3) atmospheric optics, (4) radiometry and photometry, and (5) history of science and techniques.
Direct solar irradiance spectra under clear skies have been carefully measured in a rural station in the region of 'Castilla y Leon' of typical continental climate during 1995 in order to determine the physical and radiative characteristics of atmospheric aerosols in this area. About 300 spectra have been performed with a LI-1800 spectroradiometer with a spectral resolution of 6 nm from 300 nm to 1100 nm and a wavelength sampling of 1 nm. This high-moderate spectral resolution allowed us to retrieve the experimental spectral aerosol optical depth (AOD) using spectral windows of non-absorption modeling it by the Angstrom formula. These modeled AOD spectra was taken, instead of the experimental one, in order to determine the columnar particle size distribution of atmospheric aerosols using the Mie theory and a pseudo-inversion method. We have assumed a monomodal lognormal function with a fixed standard deviation of (sigma) equals 2.5 and two particle refractive indices based on climate characteristics of our continental are of study.
We have determined the vertical integrated water vapor of the atmosphere based on the absorption features of the 940- nm band by means of ground-based measurements of direct solar spectral irradiances and modeled ones. The experimental irradiance data were performed under clear skies with a LIcor 1800 spectroradiometer, based on a monochromator system, of high to moderate spectral resolution in the 300-1100 nm range. The modeled data are based on the monochromatic approaches for atmospheric transmittance constituents, where for water vapor we used the band-model transmittance of LOWTRAN7 code. The method here used is a curve fitting procedure making use of the whole shape band absorption information and the contribution of molecular and aerosol constituents retrieving a unique water vapor value. The method were used to determine water vapor values for the period from March to November of 1995 at a rural station in Valladolid under different atmospheric conditions. The contribution of continuum absorption was also evaluated in the retrieval, obtaining lower values from 13 to 30 percent. This contribution appears as considerable greater than those expected.
Airborne imaging spectrometers, like DAIS (Digital Airborne Imaging Spectrometer) sensor, are powerful tools to monitor surface biophysical parameters, but need atmospheric correction to be compared to reference spectra. The aim of this work is the atmospheric correction of the DAIS images acquired by DLR during a flight campaign in the area of Les Gavarres (Girona, NE Spain). Experimental atmospheric measurements of direct and global irradiances together with downward radiance allow us to monitor the atmospheric radiative properties in order to carry out the atmospheric correction. An operational algorithm has been developed to process the DAIS images at low-time cost in the visible and near infrared; range (from 500 to 1100 nm).
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