The nonlinear conductivity of 2D electron gas in graphene and 3D electron gas in the narrow-gap n-InSb semiconductor has been simulated in terahertz (THz) range by various methods including the direct quantum approach, the quasi-classical kinetics, and the quasi-relativistic hydrodynamics. These methods yield the same results under the electron temperatures <= 100 K when the kinetic electron effective mass used in the nonlinear hydrodynamics is equal to the effective mass in n-InSb and it is equal to some nonzero mass that depends on 2D electron concentration in the graphene. The linear resonant dependencies of the complex electron conductivity are simulated both from the kinetic theory and from the hydrodynamic one. The kinetic dependencies of the resonant conductivity on frequency coincide with ones obtained from the hydrodynamic theory under realistic electron concentrations and collision frequencies. Thus, the nonlinear hydrodynamic equations are valid to describe the nonlinear dynamics of the electron gas in graphene and in n-InSb. The nonlinear hydrodynamics has been applied for simulations of nonlinear propagation of THz electromagnetic waves through the multilayer structures dielectric - graphene or n-InSb - dielectric placed in a bias magnetic field. The simplest three-layer structures demonstrate the sharp nonlinear switching of the transparency of THz waves and the bistability under relatively low values of amplitudes of the incident electromagnetic wave.

The nonlinear propagation and interaction are theoretically investigated of two-dimensional and three-dimensional terahertz electromagnetic beams of different polarizations in nonlinear crystals. The attention is paid to paraelectric crystals like SrTiO 3 at the temperatures 50 - 200 K. The interacting wave beams are subject to the modulation instability that results in the formation of the sequences of short envelope pulses of 2-10 picoseconds durations from the long input envelope pulses. The energy transfer from the pulse with the higher input amplitude to one with the smaller input amplitude occurs. The initial focusing of the beams compensates the wave losses and reduces the input amplitudes for observing the modulation instability.

The resonant linear and nonlinear properties in terahertz range of 2D materials graphene and silicene placed into an external magnetic field are investigated theoretically. The linear resonant dependencies of the tensor complex conductivity are computed from the kinetic theory. When the electromagnetic frequency is close to the cyclotron one, the conductivity increases sharply.The dependencies of the tensor conductivity on frequency coincide with ones obtained from the hydrodynamic theory under realistic electron concentrations and collision frequencies. The same is valid for the nonlinear dependencies of the densities of electric current on the applied terahertz electric field. Thus, the nonlinear hydrodynamic equations are valid to describe the nonlinear resonant electromagnetic wave propagation in the multilayer structures dielectric - graphene or silicene.

The resonant nonlinear scattering of terahertz electromagnetic waves by the dielectric structure with a periodic system of graphene strips is investigated theoretically. The strong electron graphene nonlinearity and the electron dissipation are taken into account. The nonlinear electron dynamics is considered within the pseudo-relativistic hydrodynamic equation. The effective matrix algorithm jointly with the iteration procedure for the nonlinearity has been applied. This structure has a high quality factor. The resonant nonlinear switching of the reflection and transmission occurs in this system.

Nonlinear terahertz waves are investigated theoretically in hyperbolic metamaterials with 2 elementary layers, nonlinear dielectric and semiconductor ones. The crystalline non-polar ferroelectric SrTiO 3 is used as a nonlinear dielectric, the narrow-gap semiconductors like InSb, InAs are used as the second layer. In different frequency ranges the dispersion dependencies are topologically different and the frequency ranges of hyperbolicity are specified. The frequency ranges for observation of spatial solitons and collapsing pulses with wave bullets are pointed out. The wave bullets are forming under the stabilization of the collapse due to the saturation of the nonlinearity and due to the wave dissipation.

The set of the nonlinear wave transformations and generation in THz range are proposed. The approach for generation of THz oscillations by carrier drift in Graphene-(Dispersive) Dielectric structure with controlling external nmagnetic field is proposed. New idea of generation of THz plasmon-polaritons in Graphene-Hyperbolic metamaterial structure with external magnetic field and electron drift in graphene is proposed, to provide the effective control over the parameters of generated waves. Superheterodyne amplification of electromagnetic waves (EMWs) of THz range in the system dielectric-semiconductor with negative differential conductivity-dielectric is proposed. High effectiveness of the self-modulation and third harmonic generation with the scattering of THz electromagnetic waves on the controllable nonlinear resonant metasurface with periodical graphene strips on the dielectric substrate is justified by modeling.

It is investigated the formation of regular sequences of short envelope pulses in terahertz range in different nonlinear crystals due to the modulation instability. The cases of the nonlinear paraelectrics and narrow-gap semiconductors are considered. The initial focusing of the input long pulses is applied. In paraelectrics the modulation instability occurs in the longitudinal direction only whereas in the narrow-gap semiconductors it takes place in all directions. It is shown that in the nonlinear paraelectrics the approximation of the pure cubic nonlinearity is satisfactory for a description of the modulation instability. In the nonlinear semiconductor plasma it is necessary to take into account the saturation of nonlinearity. There exists some interval of amplitudes of the input pulses where the formation of the regular sequences of short pulses is possible.

Nonlinear propagation of short terahertz pulses in the layered structures dielectric -graphene -dielectric … is investigated theoretically on the base of direct simulations of the Maxwell equations and the hydrodynamic equations for electrons in graphene layers. The using of the nonlinear hydrodynamics is justified from a comparison of quasi -classical kinetics, quantum kinetics, and the hydrodynamics. The effective electron mass has been determined for the hydrodynamics. The numerical FDTD scheme is proposed to consider the boundary conditions at graphene sheets. The resonant generation of odd harmonics of THz radiation has been investigated.

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.

It is investigated theoretically a possibility of propagation of terahertz envelope solitons and collapsing pulses in narrow-gap semiconductors along a bias magnetic field. The quasi-relativistic electron nonlinearity is considered. The equivalence of the semi-classical kinetic approach and the hydrodynamic one is demonstrated. For low frequency helicon waves strict limitations for the realization of envelope solitons and collapsing pulses are pointed out. At higher frequencies the frequency intervals for envelope temporal and spatial soliton propagation and the wave collapse are determined. The bias magnetic field controls the nonlinear wave dynamics there.

The resonant linear and nonlinear transmission properties in THz range of structures dielectric-metal-dielectric. are investigated theoretically. The thicknesses of metallic Ag or Au layers are of about 10 nm. The dynamics of the degenerated electron gas is described within the framework of the quantum hydrodynamic equations where the Bohm term is taken into account. To observe the resonant transmission, at the input there is a dielectric with a higher permittivity, whereas at the output is air. The incidence angle is chosen slightly below the full internal reflection angle. Because the nonlinearity of noble metals is high and almost dissipative, the nonlinearity results in the increase of the electron collision frequency. The transmission of THz electromagnetic waves increases sharply with the increase of the collision frequency. Thus the high dissipative nonlinearity in metals may play positive role in THz range for observing nonlinear phenomena in structures with thin metallic layers.

Pursuing the work developed by J. H. Eberly and coworkers [1], for free fields, that related entanglement and the spin-polarization coherence Matrix. We explore for a fully solvable QED model, the Cross-Cavity Jaynes-Cummings Model.

The nonlinear electromagnetic (EM) phenomena in terahertz (THz) range in the crystalline SrTiO3 are investigated theoretically. The goal is to investigate possibilities of the forming of short THz EM pulses. The moderate cooling T ≈ 77 K is considered. The self-action of input long envelope and baseband pulses leads to the modulation instability due to the cubic nonlinearity and frequency dispersion and to the generation of the regular sequences of short THz envelope or baseband pulses at the output of the crystal. Under the resonant nonlinear interaction of two counterpropagating EM waves with the acoustic wave of the difference frequency also the modulation instability occurs that leads to the chaotic wave modulation.

It is investigated the frequency multiplication of terahertz electromagnetic radiation in dielectric waveguides on the base of the crystalline paraelectric SrTiO3 at the temperatures 77 K when a bias electric field is applied. The frequency dispersion and the transverse width of the waves affect the generation of higher harmonics. It is possible to select the certain numbers of higher harmonics due to an optimum length of the waveguide, its width, and due to the focusing of the first harmonic. The efficiency of frequency conversion is high and can reach the values >50% in the case of focusing.

In this work we discuss the way in which, in principle, the nonzero elements in the second-order susceptibility tensor are calculated in crystal. Group Theory predicts which one of these elements will be zero based on the symmetry of the crystal. However, the position of these zeros in the tensor are intrinsically associated to fixed system of reference chosen a priori for particular crystal

It is investigated the modulation instability of transversely bounded long THz pulses in waveguides on the base of the paraelectric SrTiO3 at the temperatures 77 K. The cubic nonlinearity and the frequency dispersion correspond to existence of envelope solitons and the modulation instability of long input pulses, whereas in the transverse direction the instability is absent. There exists a possibility to generate the regular sequences of short THz pulses due to the modulation instability in the waveguides with SrTiO3. The focusing of input long pulses reduces the threshold of modulation instability at relatively low frequencies. At higher frequencies near the soft mode frequency the regular sequence of pulses can be generated in the waveguides with optimum widths.

Get PDF Email Share Share with Facebook Tweet This Post on reddit Share with LinkedIn Add to CiteULike Add to Mendeley Add to BibSonomy Get Citation Copy Citation Text G. Lopez-Galmiche, J. Escobedo-Alatorre, M. Basurto-Pensado, and J. J. Sánchez-Mondagon, "Numerical Modeling of a Mode Selective Photonic Lanterns using the Beam Propagation Method," in Frontiers in Optics 2016, OSA Technical Digest (online) (Optica Publishing Group, 2016), paper JW4A.40. Export Citation BibTex Endnote (RIS) HTML Plain Text Citation alert Save article

In this article, the comparison of excitation in high frequencies of acoustic-electromagnetic wave in piezoelecric crystal and crystal with potential of deformation GaAs is investigating. Possible mechanisms of coupling different hybrid waves are the piezoeffect and the deformation potential. As a model it is analyzing a film of crystal places between two symmetrical substrates with the other materials without an acoustic contact. This film includes 2D electron gas with a high negative differential conductivity and uniform initial distribution of electrons. The hybrid acoustic-electromagnetic wave and hybrid space charge wave interact. Amplification of space charge wave takes place due to negative differential conductivity in GaAs. This amplification of space charge waves is causing the amplification of acoustic-electromagnetic wave. It is to show that the symmetric modes, emerging as transverse ones, interact more effectively with the space charge waves. Another important result is the following: at the frequencies f ≈ 10 GHz, the excitation efficiency of acoustic-electromagnetic wave with transverse displacement due to piezoeffect is more effective, but at higher frequencies, the deformation potential is dominating.

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 photo-detector 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 degrees, 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.