We study nonlinear wave phenomena in hyperbolic and plasma-like dielectric isotropic metamaterials, dielectric-graphene (DG), dielectric-semiconductor (DS) and dielectric-metal (DM) plasma-like media (PM) (DGPM, DSPM, DMPM, respectively). When a THz beam passes through a layered DGPM in the presence of external magnetic field, we show the ability to effectively control the resonant complex nonlinear conductivity of graphene and modulation of the beam amplitude. In the hyperbolic nonlinear active IR field concentrator, the possibilities of (i) forming three types of focused nonlinear wave structures and (ii) the quasi-chaotic behaviour of the field amplitude inside the region of focusing in the above-threshold regime are demonstrated. Non-stationary regime for incident beam is included into consideration. When pulses in the IR range impinge a layer of a planar hyperbolic metamaterial with gain-active inclusions providing resonant nonlinear dissipation, the formed wave beam demonstrates pronounced synergistic behaviour with both “absorption” and “survival” phenomena. In a multilayer DMPM operating in the THz range, the transmission of a wave beam happens with the nonlinear medium transparency, whereas the medium nonlinearity is manifested via the nonlinear conductivity/nonlinear losses. In this case, quantum effects in thin metal layers were taken into account. They led, in particular, to nonlocality of the medium response. These and other theoretically revealed effects are experimentally realizable, provided with estimates for the parameters of structures and materials, and can be useful in creating effectively controllable nonlinear modulators, limiters, concentrators, sensors, devices with harmonic generation and frequency mixing, and other devices.
Due to the diversity and multiple energy domains involved, Micro-Electromechanical Systems MEMS devices are vulnerable to several mechanical failures such as fatigue. They been widely used in military applications, radio frequency systems, pressure sensors, automotive industry, among several others. Most MEMS devices contain moving parts that are subjected to cyclic loading, which degrade the device´s efficiency. Due to the high importance of MEMS in various applications, it is necessary to know their lifetime to prevent any damage or process discontinuity to which the system is subject. There have been several investigations in particular on the fatigue analysis in presence of cracks, however in terms of lifetime under cycling load, information is not abundant. The fatigue analysis can be performed for characterizing the ability of materials to support many cycles. Some parts of systems are exposed to strong stress level experiences during its usable lifetime, so the analysis must be focused on them. In this paper, a simulated fatigue analysis of classic, Z-shape and optimized chevron with Z shape arms is shown. Simulations are made using Ansys 15.0, to obtain the arms lifetime of the system because they are subjected to greater stresses in the presence of cyclic loading.
For illumination sources designers is important to know the illumination distribution of their products. They can use several viewers of IES files (standard file format determined by Illuminating Engineering Society). This files are necessary not only know the distribution of illumination, but also to plain the construction of buildings by means of specialized softwares, such as Autodesk Revit. In this paper, a complete portable system for luminaries’ characterization is given. The components of the systems are: Irradiance profile meter, which can generate photometry of luminaries of small sizes which covers indoor illumination requirements and luminaries for general areas. One of the meter´s attributes is given by the color sensor implemented, which allows knowing the color temperature of luminary under analysis. The Graphic Unit Interface (GUI) has several characteristics: It can control the meter, acquires the data obtained by the sensor and graphs them in 2D under Cartesian and polar formats or 3D, in Cartesian format. The graph can be exported to png, jpg, or bmp formats, if necessary. These remarkable characteristics differentiate this GUI. This proposal can be considered as a viable option for enterprises of illumination design and manufacturing, due to the relatively low investment level and considering the complete illumination characterization provided.
A complete adjustable and automated system has been developed on the base of three blocks: the first one is the mechanical and adjustable structure, which is composed by a mobile base and a rectangular arc, where the photodetector is located. The structure describes semi-spherical trajectories by means of two servomotors. Its lightweight and robustness constitutes two advantages which make it portable. The second stage corresponds to the automation of the structure movements. For controlling the motors and data acquisition, a microcontroller is employed that in turns helps keeping the cost of the overall system low. One of the servomotors is located on the lateral axis of the device; that displaces the sensor along a semi-circular trajectory of 160°, almost half meridians; the other one is located at the base of the illumination source, which enables it to realize an almost complete rotation around its axis. Finally, the last stage is formed by the graphical interface. The communication protocol between the data acquisition stage and the computer is USART. The graphical user interface (GUI) is developed using Visual C#. In the same window the data acquisition deployment and the data graph generator are given; the graphs can be shown in a polar or Cartesian formats showing more than one curve, if necessary, avoiding the use of additional software. The GUI keeps the low cost of the device, obtaining a comprehensive solution to generate the irradiance patterns of light sources.
The semi-spherical meter uses a photo-detector mounted on a mobile rectangular arc, which by means of two stepper
motors describes the semi-spherical trajectories required. For controlling motors and data acquisition, a Peripheral
Interface Controller (PIC) is employed, which helps keeping the low cost of the overall system. One of the stepper
motors is located on the lateral axis of the device; that displaces the sensor along a semi-circular trajectory of 170°,
almost complete meridians. Another motor located at the base of the device enables 360° rotation of the illumination
source under test. The precision is increased by the using of two angle sensors located on the opposite lateral axis and on
the mobile base of the illumination source. Additionally, before the data obtained from the photo-detector arrive to the
PIC, a stage of signal conditioning is used. This step allows us to increase not only the precision, but also the versatility
of the meter to analyze illumination sources of different sizes and fluxes. The communication protocol between the data
acquisition stage and the computer is USART. A graphical user interface (GUI) is employed on the base of the
hyperterminal.
The number of measurement points is determined by programming the two motors. The mechanical structure provides
enough rigidity for supporting the accuracy required by the data acquisition circuitry based on a PIC. Measurement of
illumination sources of different sizes is possible by using adjustable lengths of the mobile base and the ring.
We discuss the complex dispersion relation of a one dimensional metallo-dielectric photonic crystal, produced by a
dielectric photonic crystal with extremely thin metallic inserts with the same periodicity. We have carried out the
analytical and numerical analysis. Also, we show a method to avoid the problem of solving the complicated system of
transcendental equations of the dispersion relation that was proposed previously for us and we extended it to the oblique
incidence, i.e., for calculating transversal electric and magnetic modes. Moreover, we demonstrated a metallic band gap
not only at the bottom but also at high frequencies.
The meter device presented in this work consists of a photo-detector mounted on the mechanism of a mobile rectangular
arc. One stepper motor located on the lateral axis of the device displaces the sensor along a semi-circular trajectory of
170°, almost half meridians. Another motor located at the base of the device enables 360° rotation of the illumination
source under test. This arrangement effectively produces a semi-spherical volume for the sensor to move within. The
number of measurement points is determined by programming the two stepper motors. Also, the use of a single photo-sensor
ensures uniformity in the measurements.
The mechanical structure provides enough rigidity for supporting the accuracy required by the data acquisition circuitry
based on a DSPIC. Measurement of illumination sources of different sizes is possible by using adjustable lengths of the
mobile base and the ring for a maximum lamp length of 0.16 m. Because this work is partially supported by a private
entity interested in the characterization of its products, especial attention has been given to the luminaries based on LED
technology with divergent beams. The received power by the detector is useful to obtain the irradiance profile of the
lighting source under test. The meter device presented herein is a low-cost prototype designed and fabricated using
recyclable materials only such as "electronic waste".
Antenna characteristics are chosen according to the features determined by the systems where they will be used. While
some systems require a very narrow bandwidth, others may operate with a much wider bandwidth. Some techniques used
for increasing the bandwidth of a given antenna have considered mechanical adjustment of the air layer thickness, with
the consequent change on the effective permittivity and performance. Some other systems consider a suitable choice of
feeding techniques and impedance matching network. However, approaches for reducing the bandwidth have not
received the same level of attention. Narrow bandwidth antennas are of particular interest in security and surveillance
systems. In this work we present a technique, based on the design of a pentagonal antenna array, which allows for
adjusting the bandwidth in either direction. The array is formed by an inner patch designed at the desired operating
frequency of the system and a gap coupled external ring centered at a different frequency (lower or very near the
operating frequency), which determines the potential bandwidth increment or decrement. The feed point is located on the
inner patch. As a proof-of-concept, this work offers a tuning range that goes from -40% of the center frequency up to
+50% of the center operating frequency of the patch antenna. The single patch antenna of this work was designed and
simulated at an operating frequency of 4.9 GHz on RT/Duroid 5880.
In the present work we analyze the nonlinear modes of silicon-on-insulator (SOI) nanowires and supermodes of the
coupled SOI waveguides. A generalized analysis of the nonlinear modes of silicon nanowires is given where we have
considered the scalar approximation and its vectorial nature to obtain the analytical profiles. In the scalar approximation,
the analytical analysis of the profiles of the transversal modes is based on the solutions of the Helmholtz equation for
nonlinear periodic media, where we obtain an integral solution for the intensity which is identified with the help of the
elliptic functions. Those modes are characterized by two constants of motion of particular physical significance and in
some approximations the solution could become a soliton or cosenoidal type. Therefore, we describe the solutions on
terms of the movement and integration constants. This is an important result because defines the nature of the solutions,
therein the analysis of the third order polynomials roots of those elliptic functions. The general theoretical model
includes the two-photon absorption (TPA) and the nonlinear Kerr effect implicit in the refraction index.
In this semi-spherical meter, a single detector is used to realize all measurements, which is located on the extreme of a
rectangular ring (assumed as joined two mobile branches in order to compensate the weights), describing half-meridians
from 0° up to 170°. The illumination source under test is located at the center of the mobile support, which can rotate
360° horizontally. The two combined movements allow us to obtain a semi-spherical geometry. The number of
measurement points is determined by the two step-motors located under the mobile support of the luminary and on one
of the two fixed arms, which support the mobile rectangular ring, respectively.
The mechanical arrangement has the enough rigidity to support the precision required for the acquisition stage, based on
a dsPIC. The main advantages of this arrange are: Its low costs (using recyclable materials only such as "electronic
waste"), a reliable detection based on a single photo-detector, with an integrated amplification stage, and the mechanical
design.
The received power by the detector is useful to obtain the irradiance profile of the lighting sources under test. The semi-spherical
geometry of the meter makes it useful for the analysis of directive and non directive sources, in accordance
with the angle described by the mobile ring. In this work, special attention is given to LED lamps due to its impact in
several sceneries of the daily life. A comparison between the irradiance patterns of two LED lamps is also given.
A nonlinear stack is one of the handier photonic crystals where new schemes and
methodologies can be tested. Nonlinear Stacks have shown the presence of
switching, chirping and bistability, but in practice it is hard to find nonlinear
material with the adequate physical and mechanical properties. Metallic
Nanoparticles are well known to have strong nonlinearities and their composites
show the desired nonlinear properties. The nonlinearities are Kerr when
described Quantum Mechanically and field amplitude, when described classically.
In this report we describe the band gap of such classical composite stack.
We discuss a structured 3D Dielectric Photonic Crystal with both a metallic core and a metallic shell. We
discuss the role of each one, the stack, the core as well as the cavity formed between the core and the
shell. The low frequency metallic core features becomes much more significant as it gets smaller and get
diluted by the cavity.
Metallic nanoparticles, of a few nanometers radii, show nonlinearities that are
the object of experimental and theoretical studies, in particular in the framework of
composites. A quantum mechanical analysis of such structures predict a Kerr type
nonlinearity, however quite a recent publication on a classical approach has shown
that a classical metallic nanoparticles composite shows a nonlinearity proportional
to the electric field amplitude, not to the intensity as is in the Kerr case. The
capability of filling up the core of a piece fiber with such composites open the
possibility of preparing long enough pieces of fiber with such a composite as well
as the straightforward drawing of a fiber doped with nanoparticles. In this work we
carry on the numerical simulation on such class of fibers, with the specific aim of
looking at the corresponding soliton propagation in an optical fiber with a core
doped metal nanoparticles.
In this work, the development of a spherical irradiance meter is presented. The illumination intensity measurements are
made by means of a photo-detector assembled on a mechanical setup. The received power by the detector is useful to
obtain the irradiance profile of the lighting source under test, considering a discrete set of points. This detector is located
at the edge of the mobile arm of the mechanical system, which makes a sweep considering two movements directed by
the azimuthal and zenithal angles, generating analogous paths to the terrestrial meridians, covering a semi-sphere of 27
cm of radius. The concentric trajectories consider lighting source under test at their center. The radiation pattern of each
lighting source is generated using the irradiance data and the detector positions.
The mechanical structure has a horizontal mobile base, which allows a 360° rotation. At the same time, one of its
extremes serves as base of the mobile arm, which allows the vertical movements and provides the sensor support. The
movements are controlled by step motors determining the data collection points. They also define the horizontal and
vertical resolution. The obtained data is visualized by means of a display.
Waveguides coupling have been widely studied; however, nanowaveguides of high refraction index contrast open the
opportunity of studying the nonlinear dynamics of coupled waveguides, in particular those filled with metallic
nanaoparticles composites. Those composites show a Quantum Mechanical Kerr Nonlinearity and a classical field
amplitude nonlinearity that are compared by using a iterative WKB to introduce the field nonlinearity and based in the
ensuing M matrix. The produced nonlinear supermodes show a confinement of the pulse in the waveguides and a
breaking of the coupling at small and large core waveguides.
In order to determine the irradiance profile of a directive source on a plane XY, we present an arrangement of geometry
similar to conventional scanners. It is formed by two vertical bases of a mobile rail. On this rail, a photodetector is
located, making it able to move from right to left, covering a mesh of 14x15 detection points.
The XY movements of the setup are determined by servo motors, which determine the resolution, but considering the
interest of researchers in this area, and the feasibility to use a table XY for the scanning, we implement its use as a part
of this meter. The detector is located at the corner of the mobile section. The height of the light source under test is
located at the central part of the described area.
The utilization of only one photo-detector was decided with the purpose of a higher homogeneity of the irradiance
measurements. The detector must have high stability and low noise. The resolution XY is determined by the movements
on the axes of a length determined by the DSPIC programming. The use of this device instead of commercial hardware
for data acquisition contributes to the low costs of the prototype. It was realized all the necessary tests for the generation
of reliable information, establishing the time needed to achieve the stability of the system, as well as the levels of noise
due to the presence of the detector and of the electronic elements.
This prototype has a very simple geometry and relatively low cost. It constitutes a good option to determine the
irradiance profile of directive sources.
In this work, we present the basic considerations of a solar follower, realized with a control module based on a Dspic
30F40011. The Dspic was programmed considering the basic equations to track the apparent sun position. The Dspic
programming was realized considering three fundamental blocks: Real time clock, the movement determined by the hour
angle, and the movement determined by the declination angle (based on a CD motor). The mechanical design was
realized considering a parabolic antenna used as concentrator, with a diameter of 60 cm, a depth of 6 cm, weight of
approximately 1.5 kg, made of glass fiber.
The control module is easy to use due to the LCD implementation, which indicates all necessaries entries to the correct
operation of each block. The LCD is also used to display the date, hour, and the temperature obtained by the sensor
temperature located at the antenna focus.
As a proof of the correct system calibration and operation, the shadow of the sensor temperature circuit was located at
the antenna center, during all realized probes. Due to the antenna characteristics, which were made by hands, the amount
of thermal energy is relatively small but for example, enough to heating water. The obtained temperature can be
increased by replace the antenna, without to redesign the mechanical and electronic systems because they can be used for
antennas weight until 15 kg.
This paper describes the design and experimental characterization of two optimized thermal actuators devised to operate
by means of scavenging heat from the environment. Different from the traditional MEMS thermal actuator that relies on
electric current to generate heat by Joule effect, the devices herein presented have been optimized to absorb external heat
and convert it into mechanical displacement and force. The behavior of vertical and horizontal microactuators fabricated
in a standard surface micro-machining process (PolyMUMPs) demonstrates the viability of exploiting heat from the
surrounding medium to realize batteryless microsystems. Analytical and finite element models are provided in support of
the design. Results show that fairly large and useful displacements can be achieved at commonly available operating
temperatures.
Annular Photonic structures, which occur on bulk and fibers, are Bragg structures that share both Bragg resonances and waveguiding. They are related to Photonic crystals because of their large enough refraction difference indexes (n2 - n1) that makes unavoidable to consider in full the reflected wave, well beyond the approximations required for analytical gap solitons. Effectively, their confining capabilities are or primary importance, however, the potential of those structures are substantial and deserves to be further explored. Waveguiding occurs where the structure is homogenous, and may be handled on well known methods. Nonlinear propagation has been observed on solid core Bragg fibers and the soliton distribution on a nonlinear circular and annular region have been described. Linear Photonic annular structures, such as resonators, have been studied by A. Yariv as well as on omniguide fibers. The propagation along the direction where the material is inhomogenous, and that correspond to the beam profile, is a complex task and it is the objective of this paper.
The study of nonlinear photonics crystals is quite complex and cumbersome, because of their inherent architectural complexity and, in addition, because of the nonlinearity that couples propagating and counterpropagating waves. However, they are quite attractive because of their potential capabilities, and that has lead to use different approximated methods. In a one dimensional stack, it has been successfully demonstrated that they show switching, bistability and chirping as nonlinear characteristics. Band gap solitons are a well established feature of the coupled wave equations. We have extended a method that have previously shown its success for a stack with a Kerr nonlinearity, to a much more complex structure such as an omniguide fiber, as part of our suggestion that such method could be applied to numerical or analytical methods as long as the linear solution were available. Such a restriction, hinder our ability of
getting analytical solution beyond their enabling approximations, however, it is completely adequate for the purpose of to develop devices. A comparative numerical analysis of a one dimensional photonic crystal and an omniguide fiber, made of a dielectric
and stratified linear and nonlinear media, has been carried out. They were considered as multilayer arrangements with a finite numbers of periods: linear-linear, nonlinear-linear and nonlinear- nonlinear in order to study and isolate those features. Finally, a comparison of multilayer systems with variations in the diffraction indexes profiles is presented.
The variation of rainfall intensity with height makes mandatory to look at the rainfall as close to the ground as possible, when scanning the atmosphere by means of weather radars. Weather radar measurements contain many errors, which reduce the quality of the rainfall data. In particular, ground clutter has a strong relationship with the beam elevation angle and the Digital Terrain Model (DTM) around the radar site. Clutter is present when the radar beam intercepts obstacles creating a beam blockage reflecting back part of the incident energy. Due to this relationship, it is possible to predict clutter from a DTM by calculating the amount of this "blocked" energy. We present a software tool able to manipulate a DTM in order to design a clutter predictor for weather radar. This software allows the exploring of the image (rotation, zoom in and out), calculate geographic parameters and have functions to deal with the radar propagation through the atmosphere. The software developed here, in addition, has the possibility to combine the propagation beam with the DTM in order to design a cultter predictor as well as display weather radar products to become the way standard in which all the information is viewed.
An analysis of out-coupling in a laser shows an optimum way of subtracting more output power by choosing an appropriate cavity arrangement from a high-power fiber laser. This investigation consisted in resolving analytically the effect of different cavities in our laser system and one thing that outcome was to know that a fiber laser can operate with high efficiency even with high losses in one end of the cavity (e.g. at an external diffraction grating), only if the feedback in the out-coupling end is low. Moreover, it was also found that is possible to improve the output power by reducing the feedback in the out-coupling end. Parameters considered in this resolved method are 0.1 NA, 10 μm diameter core, 200 μm inner-cladding diameter and 10 dB small-signal absorption. The fiber laser was doped with ytterbium and lases at 1080 nm, when pumped at 915 hm. The maximum pump power was set to 10 W.
We propose a new structure for an integrated variable optical attenuator using InGaAsP multiple quantum wells. The principle of operation relies on the self-imaging properties of multimode interference (MMI) waveguides. The device consists of a MMI region that is 12 μm wide by 350 μm long, with input and output waveguides that are 2 μm wide. The dimensions of the MMI are calculated such that an image of the input field is produced at the output waveguide. The last statement is true as long as the phase relation between the modes in the MMI section is kept constant. Therefore, by selectively perturbing the refractive index within the MMI section, the phase relation of the modes is altered, thereby modifying the interference properties at the output of the device. We present numerical simulations using the Finite-Difference Beam Propagation Method (FD-BPM), and demonstrate that optical attenuation is possible by selectively modulating the refractive index of a narrow region within the MMI section. A dynamic range of -37 dB can be easily obtained at a wavelength of 1.55 μm with a device insertion loss of 0.3 dB. The effects of electro-absorption on the device performance are also investigated.
The chirping of a pulse propagating on a nonlinear media is nowadays a rather well studied phenomena and we are aware that requires an appreciable propagation length to develop. A nonlinear stack of finite dimension, does not have those dimensions. Therefore, chirping in this media is a rather new feature that deserves to be studied at considerable length given the greater importance that those structures have in photonics. We present a nonlinear analysis of a finite stack, nonlinear at each media and compare it with its analytically solvable linear case. The pulse propagation is discussed, in particular we demonstrate intensity dependence of the chirp as a distinctive nonlinear signature. We show two additional nonlinear characteristics: the nonlinear switching and the bistability.
In this work, the deposit technique of amorphous films for production of optical waveguides is presented, as well as the characterization of these waveguides. The basic theory is also presented for propagation of light in waveguides.
We provide an analysis of a data beam fitting method of N data points on a circular pupil that corresponds to its
best rms fit that uses an orthogonal vectorial basis of the N data points. The solutions of many physical problems often result on finding specific solutions of basic functions Fnl(ρ,θ) with polar symmetries that also can be easily treated numerically. Unfortunately, in some other cases, the analytical
solution loss its orthogonality by the experimental data discretization, therefore become inadequate for a best rms fit
data. On the other hand, by introducing the Schmidt orthogonalization, we can get the best rms fit for the solution in the coefficients of the expansion and in Fnl(ρ,θ). In these cases, where the Fnl(ρ,θ) has a cumbersome convergence, we develop the rms fit based on Zernike like Polynomials and establish the proper transformation. We illustrate in more detail the method by developing a beam analyzer as an application.
We have experienced an Associated Degree on Engineering and a subsequent Bs on Electronic Engineering that uses Optics as the essential introduction to Modern Ondulatory Physics. This first experience in Mexico is important because the popular origin of Mexican Engineering Students, that represents the 27% of the National enrollment.
This paper deals with the non-linear parametric effects on both space charge waves (with phase velocity equal to the
electron drift velocity) and electromagnetic waves (with phase velocity equal to c1 , where c is the permittivity) in GaAs
semiconductors. If an external electric field is applied, a negative differential conductivity is obtained. Under these
conditions, the electron velocity is a function of the electric field, which is given by E =E0 + E , where E0 is the constant
part and is the variable part. The analysis of the parametric interaction of the waves in the GaAs semiconductor is realized
considering both the Maxwell's equations and the velocity function. The one-dimensional model and the axis z, as the
spreading wave direction, are chosen. The analyses of instabilities are realized -by using the Blombergen's Method. The
instability efficiency is determined by the velocity, V0, the differential mobility, jiD; and the non-linear parameter, VD;by
means of the temperature model of the Gunn Effect. The efficiency is good if the interaction parameters As and as, which
are obtained from the system formed by the Maxwell's equations and the velocity function, are optimal. At the critical field
value, Ecrit, the mobility changes its sign and becomes negative, as a result, there are obtained non-linear and linear
parametric instabilities of the interactions at fields E2Ecrjt. The nonlinear parameter Vd obtains a maximum at the optimal
value of electric field, where all linear processes are very effective.
Epitaxial metastable (GaAs)1x(Ge2)x thin films have been grown on GaAs(100) in a rf planar magnetron sputtering system
(MS), without As overpressure, throughout most of the full compositional x range. The structural and compositional
properties are investigated by high resolution x-ray diffraction (HRXRD) and secondary ion mass spectrometry (SIMS). The
SIMS depth profiles demonstrate good homogeneity of Ge concentration for all the samples. HRXRD measurements show
that the lattice constant has a nonlinear dependence on the concentration x and that a transition between zmc-blende and
diamond crystal structures occurs at x 0.35. The existence of interfacial layers and the interference between the scattered
amplitudes for the epilayer and substrate are considered negligible effects on the lattice parameter determination, and
computer simulations confirm this assumption. We propose, from SIMS, HRXRD measurements and X-ray profiles
simulations, that the lattice constant behavior is influenced by the resultant As/Ga ratio in the film.
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