We investigate electromagnetic scattering of normally irradiated gyrotropic, magneto-optical core-shell cylinders using Lorenz-Mie theory. A general expression for time-averaged electromagnetic energy inside a coated gyroelectric and gyromagnetic scatterer is derived. Using realistic material parameters for a silica core and InSb shell, we calculate the stored electromagnetic energy and the scattering anisotropy. We show that the application of an external magnetic field along the cylinder axis induces a drastic decrease in electromagnetic absorption in a frequency range in the terahertz, where absorption is maximal in the absence of the magnetic field. We demonstrate not only that the scattering anisotropy can be externally tuned by applying a magnetic field, but also that it reaches negative values in the terahertz range even in the dipolar regime. We also show that this preferential backscattering response results in an anomalous regime of multiple light scattering from a collection of magneto-optical core-shell cylinders, in which the extinction mean free path is longer than the transport mean free path. By additionally calculating the energy-transport velocity and diffusion coefficient, we demonstrate an unprecedented degree of external control of multiple light scattering, which can be achieved by either applying an external magnetic field or varying the temperature
Ayoob Hematizadeh ; Seyed Masud Jazayeri
http://ieeexplore.ieee.org/document/7945274/
This paper presents a scheme to achieve terahertz radiation by the beating of top-hat lasers in a rippled density collisional magnetized plasma. The nonlinear current at terahertz frequency arises on account of nonlinear ponderomotive force as a result of beating of the two lasers. A uniform static magnetic field which is considered parallel to the direction of lasers leads to, depending on the phase-matching conditions, propagation of right-hand circularly polarized (RCP) or left-hand circularly polarized (LCP) waves in plasma. It is found that, terahertz amplitude of RCP wave for high values of beating frequency is slightly larger than LCP wave. The contribution of magnetic field, laser index and collision frequency are discussed for the efficient terahertz radiation generation. With the optimization of these parameters, the efficiency of order of 25 percent can be achieved in the present scheme.
http://www.nature.com/srep/2015/150729/srep12646/full/srep12646.html
Terahertz (THz) technology has attracted enormous interest with conceivable applications ranging from basic science to advanced technology. One of the main challenges remains the realization of a well controlled and easily tunable THz source. Here, we predict the occurrence of a long-lived population inversion in Landau-quantized graphene (i.e. graphene in an external magnetic field) suggesting the design of tunable THz Landau level lasers. The unconventional non-equidistant quantization in graphene offers optimal conditions to overcome the counteracting Coulomb- and phonon-assisted scattering channels. In addition to the tunability of the laser frequency, we show that also the polarization of the emitted light can be controlled. Based on our microscopic insights into the underlying many-particle mechanisms, we propose two different experimentally realizable schemes to design tunable graphene-based THz Landau level lasers.
