Igor Tralle, Rzeszow University
17/10/2014, 14:00 15:00
Room P9, Mathematics Building, IST
Seminar jointly organized with CFIF.
In this work the cooperative N^2-effect is considered, that is the radiation whose power is ~N^2, where N is the number of emitters which in this case is equal to the number of nonlinear coupled oscillators which model the electrons in a bunch. We consider two different models: in first case the predicted effect is the result of combining two others, namely Gunn-effect in GaAs and undulator-like radiation which can be produced by means of microstructure with grating (microundulator). In the second case, suggested effect is in a sense similar to Dicke superradiance, however it is not the spontaneous phase coherence arising in the ensemble of two-level atoms interacting via the emitted electromagnetic field, but rather, the result of interplay of another two effects. The first one is the ’pumping wave’ acting on the electrons and which is the result of undulator field, while the second is the backward effect of radiation which is produced by elec trons moving within such microundulator. As a result, the specific phase coherence (’synchronization’) develops in the ensemble of emitters and they start to generate as a single oscillating charge Ne, while the power of emitted radiation becomes ~N^2. It is very probable, that the effect can be used for the developing of a new semiconductor-based room temperature sources of the GHz and THz-radiation.
Orador/Speaker: Prof. Igor Tralle
Instituição/Institution: Faculty of Mathematics & Natural Sciences, University of Rzeszow, Rzeszow, Poland
In 15-10-2014 / 14:00 / Physics Building, Physics Department Room, 2nd floor, IST - Alameda Campus
We propose a comparatively simple way to fabricate a metamaterial which is both gyrotropic and of simultaneously negative permittivity and permeability. The idea is to make a mixture of three ingredients, where one of them would be responsible for the negativity of , while the other two would be responsible for the negativity of . The first component of the mixture is the ’swarm’ of single-domain ferromagnetic nano-particles, immersed in a mixture of other two, silver and mercury cadmium telluride.
In the work we carried out computer simulations in the frame of proposed model in order to establish the domains of existence of such material searching through the vast parameter space. The main result of the paper can be summarized as follows. In the framework of the model, we succeeded in establishing the domains of gyromagnetic metamaterial existence, relative to all parameters characterizing the model, that is, temperature, external magnetic field, parameters of nano-particles, fraction of cadmium in Hg 1-xCdx Te - compound as well as the relative concentrations of the mixture components. Negative refraction and optical activity can be achieved only if the material is in external, however moderate magnetic field. On the other hand, in some circumstances it could be an advantage, since switching magnetic field on and off, one can trigger off left-handedness. More Information..