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Enhanced second harmonic generation of Hermitea??Gaussian laser beam in plasma having density transition
摘要： Under the combined effect of relativistic and ponderomotive nonlinearity, resonant second harmonic generation of an intense Hermite–Gaussian (H–Gaussian) laser beam in a plasma having upward density ramp profile has been theoretically investigated. Under WKB approximation and with the use of the moment theory approach the coupled differential equations are derived which govern the spot size of the H–Gaussian laser beam. The ponderomotive force creates the density gradient in the background plasma electrons which is responsible for the excitation of the electron plasma wave. The large-amplitude electron plasma wave interacts with the fundamental beam which produces coherent radiations with double the frequency of the incident beam. In addition, the Gouy phase shift is observed for the H–Gaussian laser beam in plasma under the effect of density transition. The analysis shows the vital role of the different modes of the H–Gaussian laser beam and density ramp on the efficiency of generated harmonics and self-phase shift of laser beams in plasma.
关键词： ponderomotive,density ramp,second harmonic generation,relativistic nonlinearity,Hermite–Gaussian laser beam
更新于2025-09-19 17:13:59
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Nanoplasma properties in metallic clusters driven by a Gaussian laser beam in the presence of helical magnetic undulator
摘要： The motivation of present paper is the investigation of effective permittivity and absorption cross section of cluster nanoplasmas in the interaction of a Gaussian laser beam with a cluster of metallic nanoparticles, in the presence of a helical magnetic undulator. The static magnetic field of the undulator couples with the field of the laser wave, and forms a nonlinear force in the interaction region. As a result, the nonlinear force varies the plasmonic oscillations of the electron of nanoplasmas that leads to electron density modulation, which modifies absorption cross section and effective permittivity of nanoparticles. Using a perturbative method, we analytically derived the nonlinear dispersion waves and dielectric constant of metallic nanoparticles lattice (gold, silver, and copper) in the presence of a helical magnetic undulator. Numerical results indicate that with increasing the undulator magnetic field strength, absorption cross section of cluster nanoplasmas increases and absorption phenomenon occurs at frequencies close to the effective plasma frequency. Besides, with decreasing distance of nanoparticles in the cluster (and with increasing the nanoparticles radius), absorption cross section increases. We also found that the dielectric constant of the cluster nanoplasma medium increases with enhancing undulator magnetic field strength only near the effective plasmonic frequency. This concept opens a path toward new properties of cluster nanoplasmas as quantum dots, diagnostics, and sensors based on magnetic undulator structures.
关键词： Gaussian laser beam,Effective permittivity,Metallic clusters,Nanoplasma,Absorption cross section,Helical magnetic undulator
更新于2025-09-19 17:13:59
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Wave Propagation Concepts for Near-Future Telecommunication Systems || Light Wave Propagation and Scattering Through Particles
摘要： The study of light propagating and scattering for various particles has always been important in many practical applications, such as optical diagnostics for combustion, monitoring of atmospheric pollution, analysis of the structure and pathological changes of the biological cell, laser Doppler technology, and so on. This chapter discusses propagation and scattering through particles. The description of the solution methods, numerical results, and potential application of the light scattering by typical particles is introduced. The generalized Lorenz-Mie theory (GLMT) for solving the problem of Gaussian laser beam scattering by typical particles with regular shapes, including spherical particles, spheroidal particles, and cylindrical particles, is described. The numerical methods for the scattering of Gaussian laser beam by complex particles with arbitrarily shape and structure, as well as random discrete particles are introduced. The essential formulations of numerical methods are outlined, and the numerical results for some complex particles are also presented.
关键词： Gaussian laser beam,generalized Loren-Mie theory,light scattering,numerical method,small particles
更新于2025-09-09 09:28:46