RESUMO
The concept of gauge field is a cornerstone of modern physics and the synthetic gauge field has emerged as a new way to manipulate particles in many disciplines. In optics, several schemes of Abelian synthetic gauge fields have been proposed. Here, we introduce a new platform for realizing synthetic SU(2) non-Abelian gauge fields acting on two-dimensional optical waves in a wide class of anisotropic materials and discover novel phenomena. We show that a virtual non-Abelian Lorentz force arising from material anisotropy can induce light beams to travel along Zitterbewegung trajectories even in homogeneous media. We further design an optical non-Abelian Aharonov-Bohm system which results in the exotic spin density interference effect. We can extract the Wilson loop of an arbitrary closed optical path from a series of gauge fixed points in the interference fringes. Our scheme offers a new route to study SU(2) gauge field related physics using optics.
RESUMO
In this work, based on the use of the concept of spoof surface plasmon polaritons (spoof SPPs), we propose a novel kind of microstrips to suppress the interference between bended parallel microstrips. This novel structure is implemented by introducing subwavelength periodic structures onto the sides of a conventional microstrip. We numerically analyze the transmission characteristics of such new microstrips. We also measure the suppression arising from crosstalk between the bended corrugated microstrip and the conventional microstrip in both frequency and time domains. Experimental results show that such transmission line structure has superb interference restraining properties. Additionally, transmission properties have been investigated using circuit model. It is found that the coupling effect between the corrugated microstrip and the conventional microstrip can be efficiently suppressed in high speed digital signal transmission application.
RESUMO
In this paper, we propose a new metallic cylindrical antenna at terahertz frequencies using the concept of low-frequency spoof surface plasmon polaritons (SPPs). The antenna is developed by introducing an open hollow ring (OHR) in each unit cell of the conventional periodic subwavelength corrugated metallic wire (PSCMW). The new structure is referred to as the PSCMW-OHR. The dispersion properties of PSCMWs and PSCMW-OHRs, the near-field and far-field distributions, as well as the radiation efficiencies are numerically evaluated and compared. By analyzing the numerical results, we find that there are extra new propagation modes that exist in the annular groove of the PSCMW-OHR, aside from the normal transmission modes in the PSCMW. Moreover, the dispersion line of the new SPP mode exhibits a negative slope. Surprisingly and interestingly, after passing through the light line, the propagation gets into the radiation zone, where it becomes a leaky mode with a complex-valued propagation constant. We have found that the far-field radiation of propagation in the leaky mode can lead to frequency scanning effects with a scanning angle of 22°, and the radiation efficiency can be increased to 90%, provided that the total number of the periodic unit cells is large enough.
RESUMO
Based on the concept of low-frequency spoof surface plasmon polaritons (spoof SPPs), a kind of leaky mode is proposed in a waveguide made of a subwavelength metal-block array with open slots. Numerical results reveal that a new transmission mode is found in the periodic subwavelength metal open blocks. This modal field is located inside the interior of a hollow block compared with that in a solid metal block array. The dispersion curve shows that such a new SPPs mode has a negative slope, crossing the light line, and then going into a zone of leaky mode at higher frequencies. The leaky mode has a wider frequency bandwidth, and this can lead to a radiation scanning angle of 53° together with high radiation efficiency. Based on the individual characteristics exhibited by a frequency-dependent radiation pattern for the present leaky mode, the waveguide structure can have potential applications such as frequency dividers and demultiplexers. Experimental verification of such a leaky mode at microwave has been performed, and the experimental results are found to be consistent with the theoretical analysis.
RESUMO
A new scheme is suggested to manipulate the probe transitions (and hence the optical properties of atomic vapors) via double-control destructive and constructive quantum interferences. The influence of phase coherence between the two control transitions on the probe transition is also studied. The most remarkable feature of the present scheme is that the optical properties (absorption, transparency and dispersion) of an atomic system can be manipulated using this double-control multi-pathway interferences (multiple routes to excitation). It is also shown that a four-level system will exhibit a two-level resonant absorption because the two control levels (driven by the two control fields) form a dark state (and hence a destructive quantum interference occurs between the two control transitions). However, the present four-level system will exhibit electromagnetically induced transparency to the probe field when the three lower levels (including the probe level and the two control levels) form a three-level dark state. The present scenario has potential applications in new devices (e.g. logic gates and sensitive optical switches) and new techniques (e.g. quantum coherent information storage).
RESUMO
The theoretical mechanism for realizing a negative refractive index material in an optical frequency range with an atomic gas system of electromagnetically induced transparency (EIT) is studied. It is shown that under certain conditions such a dense gas can exhibit simultaneously negative permittivity and negative permeability, and negligibly small loss.
