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Electromagnetic detection of a perfect carpet cloak.

Shi X, Gao F, Lin X, Zhang B - Sci Rep (2015)

Bottom Line: It has been shown that a spherical invisibility cloak originally proposed by Pendry et al. can be electromagnetically detected by shooting a charged particle through it, whose underlying mechanism stems from the asymmetry of transformation optics applied to motions of photons and charges [PRL 103, 243901 (2009)].However, the conceptual three-dimensional invisibility cloak that exactly follows specifications of transformation optics is formidably difficult to implement, while the simplified cylindrical cloak that has been experimentally realized is inherently visible.On the other hand, the recent carpet cloak model has acquired remarkable experimental development, including a recently demonstrated full-parameter carpet cloak without any approximation in the required constitutive parameters.

View Article: PubMed Central - PubMed

Affiliation: Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371, Singapore.

ABSTRACT
It has been shown that a spherical invisibility cloak originally proposed by Pendry et al. can be electromagnetically detected by shooting a charged particle through it, whose underlying mechanism stems from the asymmetry of transformation optics applied to motions of photons and charges [PRL 103, 243901 (2009)]. However, the conceptual three-dimensional invisibility cloak that exactly follows specifications of transformation optics is formidably difficult to implement, while the simplified cylindrical cloak that has been experimentally realized is inherently visible. On the other hand, the recent carpet cloak model has acquired remarkable experimental development, including a recently demonstrated full-parameter carpet cloak without any approximation in the required constitutive parameters. In this paper, we numerically investigate the electromagnetic radiation from a charged particle passing through a perfect carpet cloak and propose an experimentally verifiable model to demonstrate symmetry breaking of transformation optics.

No MeSH data available.


Related in: MedlinePlus

The magnetic field of radiation emitted by a charged particle passing through the carpet cloak with velocity , where  is the phase velocity of light in the background. The particle moves to different positions from a-d. T1, T2 and T3 are the emitted transition radiation.
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f2: The magnetic field of radiation emitted by a charged particle passing through the carpet cloak with velocity , where is the phase velocity of light in the background. The particle moves to different positions from a-d. T1, T2 and T3 are the emitted transition radiation.

Mentions: Since the trajectory of the particle in the virtual space is bent while the time remains the same as that in the physical space, the speed in the virtual space increases by a factor of when the particle moves horizontally in the physical space. The virtual space is isotropic and homogeneous and Cherenkov radiation (CR) will be excited if the velocity of a charged particle is greater than the phase velocity of light in the background. This means that in the physical space, a horizontally moving charged particle will excite CR when its velocity is greater than . With reference to the phase velocity of light in the background, we choose two different velocities for the charged particle, and in the physical space, to investigate the radiation generated along the trajectory of the particle. The results are shown in Fig. 2 and Fig. 3 respectively. In both figures, the particle moves along the same trajectory . The particle’s motion can be divided into four stages: approaching the cloak, crossing the first interface between the cloak and the background, crossing the interface between the left and right parts of the cloak and finally leaving the cloak. In Fig. 2a, the particle is just approaching the cloak and there is no radiation. When it enters the cloak, a radiation labeled as T1 is emitted and forms a closed loop, which means the radiation propagates in all directions in the plane. This radiation corresponds to the sudden velocity change at point A in the virtual space (Fig. 1b), and also corresponds to transition radiation (TR) when the charged particle impinges on the boundary of the cloak at point A’ in the physical space (Fig. 1a). As shown in Fig. 2c, when the particle crosses the middle line separating the left and right parts of the cloak located at x=0 µm another TR, labeled as T2, is excited and forms a heart shape with a smaller heart shape embedded inside (the latter formed by the reflection at the bottom). It is worth mentioning that the left and right parts of the cloak are always impedance matched, even in previous experimentally realized imperfect models1314. Therefore, photons will just go through this interface as if it were not there. However, for a charged particle, this interface still causes TR which corresponds to the sudden velocity change at point B in the virtual space (Fig. 1b). As the particle leaves the cloak, as shown in Fig. 2d, it excites another TR at the back interface of the cloak, labeled as T3, which forms another closed loop. This radiation apparently corresponds to the sudden velocity change at point C in the virtual space in Fig. 1b.


Electromagnetic detection of a perfect carpet cloak.

Shi X, Gao F, Lin X, Zhang B - Sci Rep (2015)

The magnetic field of radiation emitted by a charged particle passing through the carpet cloak with velocity , where  is the phase velocity of light in the background. The particle moves to different positions from a-d. T1, T2 and T3 are the emitted transition radiation.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4441199&req=5

f2: The magnetic field of radiation emitted by a charged particle passing through the carpet cloak with velocity , where is the phase velocity of light in the background. The particle moves to different positions from a-d. T1, T2 and T3 are the emitted transition radiation.
Mentions: Since the trajectory of the particle in the virtual space is bent while the time remains the same as that in the physical space, the speed in the virtual space increases by a factor of when the particle moves horizontally in the physical space. The virtual space is isotropic and homogeneous and Cherenkov radiation (CR) will be excited if the velocity of a charged particle is greater than the phase velocity of light in the background. This means that in the physical space, a horizontally moving charged particle will excite CR when its velocity is greater than . With reference to the phase velocity of light in the background, we choose two different velocities for the charged particle, and in the physical space, to investigate the radiation generated along the trajectory of the particle. The results are shown in Fig. 2 and Fig. 3 respectively. In both figures, the particle moves along the same trajectory . The particle’s motion can be divided into four stages: approaching the cloak, crossing the first interface between the cloak and the background, crossing the interface between the left and right parts of the cloak and finally leaving the cloak. In Fig. 2a, the particle is just approaching the cloak and there is no radiation. When it enters the cloak, a radiation labeled as T1 is emitted and forms a closed loop, which means the radiation propagates in all directions in the plane. This radiation corresponds to the sudden velocity change at point A in the virtual space (Fig. 1b), and also corresponds to transition radiation (TR) when the charged particle impinges on the boundary of the cloak at point A’ in the physical space (Fig. 1a). As shown in Fig. 2c, when the particle crosses the middle line separating the left and right parts of the cloak located at x=0 µm another TR, labeled as T2, is excited and forms a heart shape with a smaller heart shape embedded inside (the latter formed by the reflection at the bottom). It is worth mentioning that the left and right parts of the cloak are always impedance matched, even in previous experimentally realized imperfect models1314. Therefore, photons will just go through this interface as if it were not there. However, for a charged particle, this interface still causes TR which corresponds to the sudden velocity change at point B in the virtual space (Fig. 1b). As the particle leaves the cloak, as shown in Fig. 2d, it excites another TR at the back interface of the cloak, labeled as T3, which forms another closed loop. This radiation apparently corresponds to the sudden velocity change at point C in the virtual space in Fig. 1b.

Bottom Line: It has been shown that a spherical invisibility cloak originally proposed by Pendry et al. can be electromagnetically detected by shooting a charged particle through it, whose underlying mechanism stems from the asymmetry of transformation optics applied to motions of photons and charges [PRL 103, 243901 (2009)].However, the conceptual three-dimensional invisibility cloak that exactly follows specifications of transformation optics is formidably difficult to implement, while the simplified cylindrical cloak that has been experimentally realized is inherently visible.On the other hand, the recent carpet cloak model has acquired remarkable experimental development, including a recently demonstrated full-parameter carpet cloak without any approximation in the required constitutive parameters.

View Article: PubMed Central - PubMed

Affiliation: Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, 21 Nanyang Link, Singapore 637371, Singapore.

ABSTRACT
It has been shown that a spherical invisibility cloak originally proposed by Pendry et al. can be electromagnetically detected by shooting a charged particle through it, whose underlying mechanism stems from the asymmetry of transformation optics applied to motions of photons and charges [PRL 103, 243901 (2009)]. However, the conceptual three-dimensional invisibility cloak that exactly follows specifications of transformation optics is formidably difficult to implement, while the simplified cylindrical cloak that has been experimentally realized is inherently visible. On the other hand, the recent carpet cloak model has acquired remarkable experimental development, including a recently demonstrated full-parameter carpet cloak without any approximation in the required constitutive parameters. In this paper, we numerically investigate the electromagnetic radiation from a charged particle passing through a perfect carpet cloak and propose an experimentally verifiable model to demonstrate symmetry breaking of transformation optics.

No MeSH data available.


Related in: MedlinePlus