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Effect of hotspot on THz radiation from Bi2Sr2CaCu2O8 intrinsic josephson junctions
, Article Applied Physics A: Materials Science and Processing ; Volume 123, Issue 8 , 2017 ; 09478396 (ISSN) ; Mohamadian, A ; Faez, R ; Sharif University of Technology
Abstract
We investigate hot spot effects on increasing THz emission of the frequency modes in a square mesa structure with constant hot spot size in different positions, without applying magnetic field. We show that in the presence of hot spot at any position, the average of emitted power intensity level is increased. The frequency modes that the position of their field concentration is more matched with hot spot position are more excited. Accordingly, in the case with hot spot located at center of a-axis or b-axis, frequency modes TM(m,n) with even indices m or n is more excited and in the case in which hot spot is located at the corner of a-axis or b-axis, frequency modes TM(m,n) with odd indices m...
Excitation and propagation of surface polaritonic rogue waves and breathers
, Article Physical Review A ; Volume 98, Issue 1 , 2018 ; 24699926 (ISSN) ; Sadighi Bonabi, R ; Sanders, B. C ; Sharif University of Technology
American Physical Society
2018
Abstract
Excitation and propagation of the surface polaritonic rogue waves and breathers are investigated by proposing a coupler free optical waveguide that consists of a transparent layer, middle negative index metamaterial layer, and bottom layer of the cold four level atomic medium. In this planar optical waveguide, a giant controllable Kerr nonlinearity is achieved by sufficient field concentration and a proper set of intensities and detunings of the driven laser fields. As a result, various kinds of temporal surface polaritonic solitons, rogue waves, and breathers can be propagated in the narrow window for electromagnetically induced transparency. We find that the giant intensity and extreme...
The end part of cryogenic H. V. bushing insulation design in a 230/20 kV HTS transformer
, Article Cryogenics ; Volume 108 , June , 2020 ; Vakilian, M ; Hekmati, A ; Fardmanesh, M ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
Appealing advantages of high-temperature superconducting (HTS) transformers are very promising for the contemporary and future power delivery systems. Cryogenic insulation technology is one of the key technologies for their commercialization. In this paper insulation design of the end part of cryogenic high voltage (H. V.) bushing of a 230/20 kV HTS transformer is developed. Analytical relations and finite element method (FEM) modelling, through application of COMSOL Multiphysics software, are employed for determination of electric field distribution in this design process. Weibull 0.1% dielectric breakdown strength has been considered as criterion for insulation design. Different shape and...