Electromagnetic microwave generation by acoustic vibrations gives rise to nanoradiophotonics

AbstractThe development of new methods for generating pulsed electromagnetic microwave radiation is currently an actively developing area of research. Schemes for microwave radiation generation with optical pumping are of great interest. In this paper we propose and experimentally demonstrate principally new method for photonic generation of microwave electromagnetic radiation. This method is based on the use of radiation of charged submicron particles oscillating at their own acoustic frequency. Laser radiation of the optical range implements an effective buildup of acoustic vibrations of submicron particles forming the system under study, according to the Raman mechanism.

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Theory of molecular difference frequency laser excitation by optical pumping under saturation conditions

Journal of Applied Spectroscopy ◽

10.1007/bf00659757 ◽

1982 ◽

Vol 36 (3) ◽

pp. 276-282

Author(s):

B. I. Stepanov ◽

S. A. Trushin ◽

V. V. Churakov

Keyword(s):

Optical Pumping ◽

Laser Excitation ◽

Difference Frequency ◽

Frequency Laser

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Effects of transverse static electric field on terahertz radiation generation by beating of two transversely modulated Gaussian laser beams in a plasma

Laser and Particle Beams ◽

10.1017/s026303461400024x ◽

2014 ◽

Vol 32 (3) ◽

pp. 375-381 ◽

Cited By ~ 15

Author(s):

Prateek Varshnety ◽

Vivek Sajal ◽

Prashant Chauhan ◽

Ravindra Kumar ◽

Navneet K. Sharma

Keyword(s):

Electric Field ◽

Ponderomotive Force ◽

Beam Width ◽

Laser Beams ◽

Thz Radiation ◽

Gradient Force ◽

Pressure Gradient Force ◽

Static Electric Field ◽

Radiation Generation ◽

Frequency Laser

AbstractResonant excitation of terahertz (THz) radiation by nonlinear coupling of two filamented spatial-Gaussian laser beams of different frequencies and wave numbers is studied in plasma having transverse static electric field. The static ponderomotive force due to filamented lasers is balanced by the pressure gradient force which gives rise to transverse density ripple, while, the nonlinear ponderomotive force at frequency difference of beating lasers couples with density ripple giving rise to stronger transverse nonlinear current which results into the excitation of THz radiation at resonance. The coupling is further enhanced by the presence of static electric field and spatial-Gaussian nature of laser beams. An increase of six-fold in the normalized amplitude of THz is observed by applying a direct current field of about 50 KV. Effects of frequency, laser beam width, and periodicity factor of modulated laser amplitude are studied for the efficient THz radiation generation. These results can be utilized for generating controlled tunable THz sources for medical applications using low filament intensities (~ 1014 W/cm2) of beating lasers.

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Superelastic electron scattering from calcium and lithium

Canadian Journal of Physics ◽

10.1139/p96-818 ◽

1996 ◽

Vol 74 (11-12) ◽

pp. 984-990 ◽

Cited By ~ 6

Author(s):

P. J. O. Teubner ◽

V. Karaganov ◽

M. R. Law ◽

P. M. Farrell

Keyword(s):

Optical Pumping ◽

Single Frequency ◽

Optically Pumped ◽

Close Coupling ◽

Pumping System ◽

State Orientation ◽

Superelastic Scattering ◽

Frequency Laser ◽

Theory And Experiment ◽

Good Agreement

Superelastic scattering experiment were performed on optically pumped calcium atoms at energies of 25.7 and 45 eV referred to the ground state. Orientation and alignment parameters derived from these experiments are compared with the predictions of several theories based on a distorted-wave formalism. The agreement between theory and experiment is unsatisfactory at the lower energy at all scattering angles. At the higher energy agreement improves at small scattering angles but is poor at middle angles. The results of our quantum electrodynamical calculation on optical pumping in lithium are compared with our observations. We find such good agreement between theory and experiment that we explore the possibility of superelastic scattering experiments on lithium atoms that are optically pumped with single-frequency laser light. A two-frequency pumping system is described and its use in the observation of superelastic scattering from lithium is discussed. Orientation and alignment parameters are presented at an equivalent energy of 21.8 eV for small angles. They are compared with those predicted by two close-coupling calculations. Excellent agreement is found between the present work and the convergent close-coupling theory of Bray.

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Strong terahertz radiation generation by beating of two x-mode spatial triangular lasers in magnetized plasma

Laser and Particle Beams ◽

10.1017/s0263034614000640 ◽

2014 ◽

Vol 33 (1) ◽

pp. 51-58 ◽

Cited By ~ 20

Author(s):

Prateek Varshney ◽

Vivek Sajal ◽

Sweta Baliyan ◽

Navneet K. Sharma ◽

Prashant K. Chauhan ◽

...

Keyword(s):

Magnetic Field ◽

Terahertz Radiation ◽

Beam Width ◽

Laser Pulses ◽

Magnetized Plasma ◽

Thz Radiation ◽

Dc Magnetic Field ◽

Radiation Generation ◽

Transverse And Longitudinal Components ◽

Frequency Laser

AbstractResonant THz radiation generation is proposed by beating of two spatial-triangular laser pulses of different frequencies (ω1, ω2) and wave numbers $\lpar \vec k_1 \comma \; \vec k_2 \rpar $ in plasma having external static magnetic field. Laser pulses co-propagating perpendicular to a dc magnetic field exert a nonlinear ponderomotive force on plasma electrons, imparting them an oscillatory velocity with finite transverse and longitudinal components. Oscillatory plasma electrons couple with periodic density ripples n′ = nq0eiqz to produce a nonlinear current, i.e., responsible for resonantly driving terahertz radiation at $\lpar {\rm \omega} = {\rm \omega} _1 - {\rm \omega} _2 \comma \; \vec k = \vec k_1 - \vec k_2 + \vec q\rpar $. Effects of THz wave frequency, laser beam width, density ripples, and applied magnetic field are studied for the efficient THz radiation generation. The frequency and amplitude of THz radiation were observed to be better tuned by varying dc magnetic field strength and parameters of density ripples (amplitude and periodicity). An efficiency about 0.02 is achieved for laser intensity of 2 × 1015 W/cm2 in a plasma having density ripples about 30%, plasma frequency about 1 THz and magnetic field about 100 kG.

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PIC simulation of a two-foil vircator

Laser and Particle Beams ◽

10.1017/s0263034617000283 ◽

2017 ◽

Vol 35 (2) ◽

pp. 362-365 ◽

Cited By ~ 5

Author(s):

A.E. Dubinov ◽

V.P. Tarakanov

Keyword(s):

Electron Beam ◽

Phase Portrait ◽

Microwave Radiation ◽

Spectral Characteristics ◽

Squeezed State ◽

Pic Simulation ◽

Microwave Generation ◽

Generation Frequency ◽

Particle In Cell ◽

Electronic Phase

AbstractParticle-in-cell (PIC) simulation of a two-foil magnetoinsulated vircator is carried out. Evolution of electron phase portrait has been studied. Formation of two regions with a squeezed state of electron beam is observed, separated from each other by an electronic phase vortex. The power of two-foil vircator's microwave generation was calculated. It is demonstrated that in the phase vortex mode, the power of vircator's microwave radiation may excel the outcome power of a usual one-foil vircator by two times. The spectral characteristics of two-foil vircators were studied. It was found that it is necessary to change the energy of electrons for the variation of primary microwave generation frequency.

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HREM observation of NiO growth on submicron spheres of pure nickel

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100154718 ◽

1989 ◽

Vol 47 ◽

pp. 548-549

Author(s):

C.M. Teng ◽

T.F. Kelly ◽

J.P. Zhang ◽

H.M. Lin ◽

Y.W. Kim

Keyword(s):

Nickel Oxide ◽

Grain Boundaries ◽

Pure Nickel ◽

Submicron Particles ◽

Crystal Formation ◽

Nickel Wire ◽

Liquid Droplets ◽

Oxide Interface ◽

Nickel Chromium ◽

Chromium Alloys

Spherical submicron particles of materials produced by electrohydrodynamic (EHD) atomization have been used to study a variety of materials processes including nucleation of alternative crystallization phases in iron-nickel and nickel-chromium alloys, amorphous solidification in submicron droplets of pure metals, and quasi-crystal formation in nickel-chromium alloys. Some experiments on pure nickel, nickel oxide single crystals, the nickel/nickel(II) oxide interface, and grain boundaries in nickel monoxide have been performed by STEM. For these latter studies, HREM is the most direct approach to obtain particle crystal structures at the atomic level. Grain boundaries in nickel oxide have also been investigated by HREM. In this paper, we present preliminary results of HREM observations of NiO growth on submicron spheres of pure nickel.Small particles of pure nickel were prepared by EHD atomization. For the study of pure nickel, 0.5 mm diameter pure nickel wire (99.9975%) is sprayed directly in the EHD process. The liquid droplets solidify in free-flight through a vacuum chamber operated at about 10-7 torr.

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