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The nonlinear baseband electromagnetic pulses of a wide spectrum that covers the lower part of terahertz (THz) range are investigated theoretically in the paraelectric crystals like SrTiO3 at the moderately low temperatures 50–200 K. The frequency dispersion is important there. The dominating nonlinearity of the crystal is cubic. To increase the influence of the nonlinearity, the focusing of the input baseband pulses of small amplitudes has been applied. The main attention is paid to the three-dimensional (3D) geometry of focusing of the input baseband pulses. The nonlinear focusing of input long baseband pulses by the exciting antenna results in the formation of extremely short baseband pulses of subpicosecond durations. Under 3D focusing the peak values of the nonlinear focused pulses are bigger and their durations are shorter than ones under 2D focusing, but the transverse localization is stronger under 2D focusing.

The superheterodyne amplification of electromagnetic waves is investigated when the resonant three-wave interaction of two electromagnetic waves with the space charge wave occurs in the waveguides nitride n-GaN, n-InN films-dielectric. The amplification of SCW waves due to the negative differential conductivity is investigated in nitride n-GaN, n-InN films at the frequencies f ≤ 400 GHz in the lower part of the terahertz (THz) range. The electromagnetic waves are either in the upper part of THz range or in the optical range. The superheterodyne amplification is considered in two geometries, the collinear one in which the three interacting waves travel in the same direction and the anti-collinear geometry where the second electromagnetic wave propagates in the opposite direction. The preferences and drawbacks of each geometry are pointed out. The finite width of space charge waves leads to decrease of increments of amplification.

It is investigated theoretically the nonlinear down-conversion of powerful extremely low frequency (ELF) modulated acoustic wave beams at the carrier frequencies 1–20 Hz into ultra-low frequency (ULF) acoustic waves at the frequencies 0.01–0.1 Hz under the propagation upwards within the atmosphere and ionosphere. The approximation of the slowly varying profile is used. It is shown that under a fixed value of the integral power of the initial acoustic ELF beam there exists the optimal value of the initial transverse width where the maximum down-conversion is realized. The different types of the modulation are considered, namely the simplest two-frequency modulation and multifrequency noise-like one. The using of the complex multifrequency modulation results in the increase of the efficiency of the down-conversion within the ionosphere E- and F-layers.

Microelectromechanical (MEM) Accelerometers measure the accelerations or vibrations experienced by objects due to inertial forces or mechanical excitations. To improve their proof mass displacement, several alternatives have been used, such as the design of different shapes of suspension beams. In this work, a new shape of beam is proposed based on alternated segments of different widths. To analyze its performance, one-quarter, middle and complete accelerometers were calculated and simulated, the results were compared with similar cases using conventional uniform-shaped beams. A notable improvement in the proof mass displacement was obtained in all cases, especially with the proposed symmetrical-shaped beam. Harmonic response and explicit dynamic analysis were also considered to discover performance when they are subjected to structural load. An improvement in amplitude displacement was also observed, as well as operation frequency reduction. From the explicit dynamic analysis, a faster performance of the accelerometer with uniform arms can be observed, however, it responds at a lower range of input velocities. A performance comparison of the proposed beam is presented considering the two reported accelerometers. Finally, from the variation in the width of the thinner segment of the symmetrical arms, it can be observed that it is possible to obtain an increment in the displacement of the proof mass of 39.57% and a decrement in natural frequency of 15.30%, with respect to the case of the uniform arm. Other advantages of the symmetric beam are the stress distribution, reducing its effect on the proof mass, as well as their low cross-axis sensitivity. Simulations were performed with ANSYS.

The nonlinear waves of terahertz (THz) range are investigated in the paraelectric crystals SrTiO3 at the temperatures ~77 K. The frequency dispersion is important there. In the absence of a bias electric field the dominating nonlinearity is cubic. The frequency dispersion and nonlinearity correspond to existence of envelope solitons and the modulation instability (MI) of long input pulses, whereas in the transverse direction MI is absent. There exists a possibility to generate the regular sequences of short THz pulses due to MI in bounded SrTiO3 crystals. The focusing of input long pulses reduces the threshold of MI, increases the output amplitudes of the short pulses, and provides more stable generation of the short pulses. It is investigated the frequency multiplication of THz electromagnetic radiation in bounded paraelectric SrTiO3 when a bias electric field is applied. The dominating nonlinearity is quadratic there. The frequency dispersion and the transverse width of the input wave beams affect the generation of higher harmonics. It is possible to select the certain numbers of higher harmonics by means of the optimum length of the crystal, by the width of the beam of the input first harmonic, and by the focusing of the input first harmonic.

En este trabajo se compara el rendimiento de una antena de parche rectangular realizada sobre planos de tierra rectangular y circular, respectivamente. Se observa una mayor ganancia para el caso circular pero un menor ancho de banda. La comparación se llevó a cabo también cuando a los planos de tierra se agregaron defectos. Como resultado, se observaron cambios en las ganancias, el parámetro S11 y los anchos de banda.Para la antena rectangular sobre substrato rectangular con Defectos en el Substrato (DGS, por sus siglas en inglés) la principal mejora observada fue sobre el parámetro S11. Para el caso del plano de tierra (o substrato) circular, el ancho de banda muestra un incremento de 113.59% comparado con el caso sin defectos. Las antenas fueron simuladas utilizando el software FEKO.

The detectors based on superconductors are used for the registration of signals in the millimeter range [1]. Specially, the quantum radio receptor is widely used due to its very high sensibility. The structure of such receptor consists usually of a periodic Josephson’s Junctions (JJs) lattice and its very high sensibility may be obtained with the synchronization of the JJs using resonators of superficial electromagnetic wave [2]. These resonators realize automatically the synchronization of several hundreds of JJs, including the electro dynamical especial line like lattice [2].

One dimensional (1D), circular (2D) and spherical (3D) stacks have occupied quite an important place in Optics, Electronics and Solid State Physics on their own, that keeps growing with the development of Photonics. In particular Bragg and Photonic structures have found an application as Bragg fibers, microresonator, quantum dots like and many others structures; everything made feasible by the modern nanofabrication and others fabrication techniques. Their structural complexity still relies heavily on numerical simulation, with the exception of a few accessible cases. Among them, we study the scaling of a Bragg resonance (1/4 λ ) stack from one-dimensional to circular and spherical structures, from the point of view of their photonic band gap. The similitude with the well known linear multilayer method is discussed.

A superheterodyne amplification of sub-millimeter electromagnetic waves in GaAs due to the negative differential mobility is analyzed. The nonlinearity arises from the modulation of concentration, due to a space charge wave, and from the ponderomotive force, due to electromagnetic waves. The case of resonant interaction of two traveling counter propagating electromagnetic waves and the space charge wave in a thin n-GaAs film placed into a dielectric waveguide is considered. The case of 2D electron gas is also analyzed. The simulation of this nonlinear interaction shows a certain increment of the amplification.

The superheterodyne amplification of sub-millimeter electromagnetic waves in GasAs due to negative differential mobility is analyzed. The nonlinearity arises from the current and the magnetic field of the electromagnetic waves. The case of interaction of two traveling counter propagating electromagnetic waves and the following space charge wave in an n-GaAs film, placed onto i-GaAs substrate, is considered, under a 2D electron gas model. The simulation of this nonlinear interaction shows a certain amplification of the sub-millimeter electromagnetic wave.

This paper deals, at first, with the non-linear parametric effects on both space charge and electromagnetic waves in GaAs semiconductors. If an external electric field is applied, at the critical field value, the mobility changes its sign and becomes negative, as a result, non-linear instabilities of the interactions are obtained. At the optimal value of electric field, Eopt, all non-linear processes are very effectives. The second point is the multiplication of the wave frequency, which is also effective thanks to the non-linearity. This process is used for carring waves into millimeter range instead of generation process, which in this range is non-effective. The Multiplication effect is based on the using space charge waves.

The capacitive accelerometers based on microelectromechanical systems (MEMS), are widely used in the automotive industry, in seismic detection, and in military applications. The sensitivity is one of their main characteristics, which widely benefit their use in front of small acceleration changes. In this work, the elements considered in the analyses of these systems are mass and suspension beams, which constitute a mass-spring system. The mathematical modelling establish its mechanical response. Based on the equations of sensitivity and frequency of displacement response sets out the criteria to determine the geometry of the mass and the length of suspension beams are obtained in order to improve the sensitivity response. The importance of the stiffness constant is also considered as part of the design. Inthis case, the changes in the mass produces irregular geometries that, at the same time, allows to increase the beam’s length. The improvement in the sensitivity value permits the actuation at lower levels of acceleration. In addition, the simulation of the vibration mode, corresponding to the in-plane displacement, is carried out with the purpose of determining the appropriate frequency for the system operation. Material used for the actuator implementation is silicon. ANSYS is the software used to carry out simulations and characterization of the analyzed systems.

Excitation of microwave, wide spectrum ƒ ≤ 1 GHz, nonlinear solitary acoustic monopulses, propagating along the interface between a solid film and a solid substrate, is theoretically analyzed. A quadratic elastic nonlinearity in both contacting media of the system is taken into account in the case of baseband waves. The transverse inhomogeneity and diffraction in the interface plane are considered. The baseband waves are not true monopulse-like solitons and manifest as single shock-like pulses in the case of an excitation from initial long rectangular pulses. The transverse inhomogeneity affects the dynamics of the shocks, and there is a possibility to focus the monopulses.

In previous works, we presented the development of a semi-spherical prototype irradiance meter. On the base of this device, we obtain the radiation patterns of two illumination sources, considering only nine sensors.

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.

In this work we discuss the control of a solar concentrator located at Temixco, Morelos, Mexico. This place accounts with the greatest constant illumination in Mexico. For the construction of the concentrator we use a recycled parabolic plate (NEC). This plate was totally covered with aluminum. Its opening diameter is of 332 cm, the focal length is of 83 cm and the opening angle is of 90deg. The geometry of the plate guarantees that the incident beams, will be collected at the focus. We obtain up to 2000degC of temperature concentration with this setup. In order to optimize the operation of the concentrator we use a control circuit designed to track the apparent sun position.

The equidistant detector distribution on a circular path is quite convenient for detection, but should be related with an spherical description and this is the object of this work.

The design of a semi-spherical irradiance profile detector (SD) is shown. With this device, we obtain the distribution of illumination due to punctual sources in the visible range. This meter can be also used as quality control device for lamps and bulbs. We are interested in the distribution of the irradiance, instead of the total irradiance over a complete region, which is the information given by spherical meters, such as the Ulbrich spheres. The obtained discrete profiles corresponds to the irradiance, as equivalent to the voltage intensity detected in semispherical detector basic sensor. These voltage values permit us to obtain the corresponding profile to each source and give as the capability to chose the better sources for specifics tasks.

To bypass the non orthogonality of the corresponding spherical harmonics on a semisphere we map the detection data on a circle, were a good data fitting is provided by the Zernike Polynomilas.

The millimeter frequency range is being intensively investigated. Novel types of oscillators, both diode-like (TUNETT) and lasers have been put forward; the search of effective control devices is also of great interest. Volume and surface oriented integrated p-i-n-structures modulators have demonstrated high efficiency in millimeter wave range. These structures possess high modulation and high-speed properties, sustain great EM powers, but their modulation characteristics in millimeter and sub millimeter range have not been yet investigated in detail. A comparison and criteria of these modulators based on silicon, in millimeter range are presented here.

Superheterodyne amplification of sub-millimeter electromagnetic waves in GaAs due to negative differential mobility is analyzed. The nonlinearity arises from the current and the magnetic field of the electromagnetic waves. The case of interaction of two traveling counter-propagating electromagnetic waves and the following space charge wave in an n-GaAs film placed onto an i-GaAs substrate is considered The case of 2D electron gas is also analyzed. The simulation of this nonlinear interaction shows a certain increment of the amplification.

The coherent coupling of a pair of Bloch Equations is used to model the coupling of a pair of Two Level Atoms in terms of their symmetric and antisymmetric states.