Ling-Bao Kong

Microwave permittivity and permeability experiments in high-loss dielectrics: Caution with implicit Fabry-Pérot resonance for negative imaginary permeability

Various materials have been examined to obtain permittivity and permeability values required for detailed investigations on functional materials like microwave-absorbing and high-permittivity dielectrics. We call for caution when samples exhibit negative imaginary permeability, whether containing a resonance peak or not. In the retrieval procedure, the Fabry-Perot resonance (FPR) can produce a negative imaginary permeability, which should be classified as an extrinsic rather than an intrinsic physical attribute. In particular, for high-loss materials, the implicit FPR would bring a plausible negative imaginary permeability. Here we have listed a dielectric dispersion of FPR behavior for BiFeO3 samples.

Efficiency enhancement of anomalous-Doppler electron cyclotron masers with tapered magnetic field

The efficiency of slow-wave electron cyclotron masers (ECM) is usually low, thus limiting the practical applications. Here, a method of tapered magnetic field is introduced for the efficiency enhancement of the slow-wave ECM. The numerical calculations show that the tapered magnetic-field method can enhance the efficiency of slow-wave ECM significantly. The effect of beam electron velocity spread on the efficiency has also been studied. Although the velocity spread reduces the efficiency, a great enhancement of efficiency can still be obtained by the tapered magnetic field method.

Numerical Study of an A-Shape Negative Refractive Index Material

Metamaterial designing is an important issue in order to reduce the complexity and for the extensive use in various potential applications. This paper presents an A-shape novel metamaterial structure which simultaneously exhibits negative permittivity and negative permeability. An electromagnetic wave simulation is performed, and the results show that the proposed metamaterial unit cell is capable of achieving a negative refractive index. Furthermore, a left hand prism was designed composed of metamaterial unit cells. Simulation of the left hand prism proves the presence of a negative refractive index. The proposed design is easy to fabricate compared to the complex structures, due to the simple geometry, and could be used in various applications.

Enhancing the efficiency of slow-wave electron cyclotron masers with the tapered refractive index

The nonlinear analysis of slow-wave electron cyclotron masers (ECM) based on anomalous Doppler effect in a slab waveguide is presented. A method of tapered refractive index (TRI) is proposed to enhance the efficiency of slow-wave ECM. The numerical calculations show that the TRI method can significantly enhance the efficiency of slow-wave ECM with the frequency ranging from the microwave to terahertz band. The effect of beam velocity spread on the efficiency has also been studied. Although the velocity spread suppresses the efficiency significantly, a great enhancement of efficiency can still be introduced by the TRI method.