Experimental Verification of Reversed Cherenkov Radiation in Left-Handed Metamaterial

Abstract

By using a phased electromagnetic dipole array to model a moving charged particle, we experimentally verified a reversed Cherenkov radiation in the left-handed media in the frequency range from 8.1 to 9.5 GHz. Our results demonstrate the feasibility of new types of particle detectors and radiation generators. DOI: 10.1103/PhysRevLett.103.194801 PACS numbers: 41.60.Bq, 41.20.Jb In 1934, Cherenkov discovered experimentally the coherent radiation when some media were bombarded by fast-moving electron beams [1]. Frank and Tamm established the theory of Cherenkov radiation (CR) in the framework of classical electrodynamics in 1937 [2]. The theory shows that CR will radiate only when the speed of the charge is larger than the speed of light in the medium. Since then, CR has been widely applied in high-energy physics. One of the important applications is Cherenkov counters, which are used to determine various properties of a charged particle such as its velocity, charge, direction of motion, and energy. These properties are important in the identification of different particles. The discovery of antiproton [3] is a good example of the application of CR, as well as the discovery of the J particle [4], in which Chen designed the six large Cherenkov counters.In conventional media, the radiation angle of CR c , which is the angle between the direction of wave propagation and charge velocity, is always between 0 and 90 . Thus, the charged particle will interfere with the detection of the forward radiated waves. In 1968, Veselago predicted the abnormal reversed Cherenkov radiation in the lefthanded metamaterials (LHMs) with simultaneously negative permittivity and permeability [5], allowing the backward emitted wave to be easily separable from the emitting particles. More theoretical frameworks have been proposed since then [6]. The first experimental attempt using a beam of charged particles with metamaterials was carried out in a waveguide [7]. Although the result cannot be decisively concluded as a backward CR, the observation of the transmission peak in the left-handed band is an indirect observation of the wakefield generation [7]. In short, experimental verification of backward CR is still very rare. The lack of LHMs for transverse magnetic (TM) polarized waves has been one of the main obstacles. Because of the rotational symmetry of the cylindrical configuration for CR, the experimental verification of the reversed CR requires metamaterials for transversely magnetic polarized waves, which requires negative permeability along the direction and negative permittivities along the and z directions. Since Pendry et al. first showed that the metallic rod arrays [8] and the split-ring resonators (SRRs) [9] exhibited negative permittivity and negative permeability, respectively, most of the LHMs realized so far have been for transverse electric (TE) polarized waves [10], which is not suitable for backward CR detection. The second reason is that the radiation power of CR increases with its frequency; therefore, the optical ...

Quantum Čerenkov Radiation: Spectral Cutoffs and the Role of Spin and Orbital Angular Momentum

“…Namely, it can also occur for classical charge distributions having a well-defined spread angle θ i , as well as in analogs of the Čerenkov effect in other areas of physics (for example, see Refs. [13,14]; similar conditions could be designed in other systems analogous to ČR [8][9][10][11][12][13][14][15][16][17][18][19]21,22]). In either case, the cone splitting we show here is uniquely tied to the shape of the incoming electron wave packet (or the charge distribution in a classical electron beam), and it is independent of material properties that can cause other kinds of cone splittings [50].…”

“…Other kinds of ČR were found in photonic crystals [15,16], tunable light sources [17], coherently driven ultracold atomic gas [18], and recently even in active gain medium [19]. Many more novel ČR effects are still being found in new settings, such as surface polaritons [20] and metamaterials [21], where recent findings suggest revolutionizing Čerenkov detectors [22]. Even nanoparticles are now being combined with the Čerenkov effect in the UV radiation from charges emitted from radioactive isotopes, allowing in-depth phototherapy [23].…”

Spectrum of Cherenkov Radiation in Dispersive Metamaterials With Negative Refraction Index

“…The investigations of optical negativeindex [1] metamaterials (NIM) using the nanostructured metaldielectric composites already have led to both fundamental and applied achievements that have been realized in various structures [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21].…”

“…Cherenkov radiation by a charged source that moves in (or in the interface) a left-handed material has been studied in number of works [15][16][17][18][19][20][21]. Both experimental and theoretical frameworks are investigated, see review [16] and references therein.…”

Change of Structure of the Cherenkov Emission at Modulated Source in Dispersive Metamaterials

“…Cherenkov radiation by a charged source that moves in a lefthanded material and has not the own frequency has been studied in number of works [17][18][19][20][21][22][23]. Both experimental and theoretical frameworks are investigated, see review [18] and references therein.…”