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Study On Propagation Properties Of Laguerre-Gaussian Beams In Negative Index Medium

Posted on:2011-02-02Degree:MasterType:Thesis
Country:ChinaCandidate:Y Y XiangFull Text:PDF
GTID:2178360308968753Subject:Information and Communication Engineering
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Negative refractive index metamaterial(NIM) is a type of special synthetic medium which has negative permittivity and negative permeability, and also known as Left-handed metamaterial. Negative refractive index medium has electromagnetic properties that are not found in nature and can be artificially tuned at will. Nowadays, the NIM has been achieved from the microwave to the optical band, which will expand the research area beam transmission and lead to many new optical phenomena and new features, and thus make it possible to obtain a new means of manipulating light. And it is considered that the NIM to be a revolutionary influence on the field of physics, electronics and communication. In this thesis, we combine the standard theory for laser optics in conventional optical material with the unique properties of NIM to study the propagation properties of Laguerre-Gaussian beams in NIM. The investigation of propagation characteristics of Laguerre-Gaussian beams in NIM not only have great scientific value, but also is expected to expand with negative refractive index medium in the control of light in application scope, which have important scientific significance and application value. The main research results are listed below:Firstly, starting from the representation of paraxial-beam angular spectrum, we established the propagation model of Laguerre-Gaussian beam in NIM. Through the study of phase distribution, we find that the rotation characteristics of the beam depend on model parameters, Gouy phase, frequency, and dispersion. It is demonstrated that the intensity rotation characteristics of the beam can be observed when there exist an azimuthally phase difference. The inverse Gouy phase shift caused by the negative refractive index induces a reversed rotation of intensity. In normal dispersion regime, the he phase and intensity exhibit the opposite rotation fashion. In anomalous dispersion one, however, the phase and intensity undergo the same rotation fashion.Secondly, we investigate the transmission characteristics of Laguerre-Gaussian beam in gradient negative index medium, and established the propagation model of Laguerre-Gaussian beam. Then, we show that the gradient refractive index of NIM gives rise to focus beam, when the nature diffraction of beam is exactly balanced by focusing, spatial soliton forming. In addition we give the conditions for the formation of spatial soliton and spatial breather in a gradient negative index medium.Finally, we study the rotation property of multimode Laguerre-Gauss beam in NIM which is represent as a superposition of Laguerre-Gaussian beams with same frequency, same magnitude, paraxial propagation. We theoretically prove that the negative refractive index of NIM gives rise to the negative Rayleigh length and negative Gouy-phase shift of multimode Laguerre-Gauss beam, and the latter one will cause a reversed rotation of transverse intensity pattern. Furthermore, we demonstrate that compared with the multimode Laguerre-Gauss beam in gradient index medium, the difference of transmission characteristics are mainly represent on rotating characteristics. Because of the reverse Gouy phase shift, the direction rotation of the multimode Laguerre-Gauss beam will also reverse.
Keywords/Search Tags:Negative refractive index metamaterial, Spatial soliton, Intensity rotation characteristics, Reverse Gouy phase shift
PDF Full Text Request
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