Resonant Radiation Field Research Articles

Analytical solutions for resonant radiation performance of bending-mode magnetoelectric antennas

This paper proposes analytical solutions for the resonant radiation performance of bending-mode magnetoelectric (ME) antennas. The strain-mediated Converse ME (CME) coupling model of bending-mode ME antennas is first established by solving nonlinear constitutive equations and bending governing equations using the elastic mechanics method. Then, the calculated magnetic flux and electric displacement are employed to propose a resonant radiation field model based on the dipole method. The numerical results for the CME coefficient show a good agreement with the experimental data. It can be observed that the volume fraction ratio of the piezoelectric layer can control the CME coefficient and radiation efficiency with the same variation trend since it can determine the bending strain via changing the location of the neutral layer of the ME antennas, which also demonstrates the strain-mediated essence of the ME antennas. In addition, the volume fraction ratio can tune the resonant frequency within a wide range. The gain of the ME antenna is stable and higher than −168 dB with the volume fraction ratio ranging from 0.2 to 0.7. The tensile stress and compressive stress have the opposite effect on the resonant frequency at low and high bias magnetic fields. Meanwhile, the tensile (compressive) stress is beneficial for both the radiation and gain in the low (high) bias field region. This model may facilitate the understanding of the bending-mode radiation mechanism of ME antennas and provide a basis for designing asymmetric ME antennas.

Theoretical and Experimental Investigations on Differential Aperture-Coupled Rectangular Laminated Resonator Antenna

This letter studies differential aperture-coupled rectangular laminated resonator antenna (LRA) theoretically and experimentally. A theoretical model is proposed to analyze the resonance and radiation characteristics of the differential aperture-coupled rectangular LRA based on mode matching method. Analytical expressions for the resonant frequencies, Q-factor, impedance bandwidth (BW), radiation fields, directivity, radiation efficiency and gain are first derived. For verification, three prototypes of rectangular LRA with different length-to-height ratios differentially fed by a coupling slot are simulated, fabricated, and measured. Acceptable agreements among the calculated, simulated, and measured results are achieved. The proposed theoretical model provides physical insight into the operating principle of aperture-coupled LRA, which can be applied to predict the performances of rectangular LRAs and to instruct the design of rectangular LRAs.

Light-induced pressure anisotropy and temperature change in atomic gases

Pressure anisotropy and radiative temperature change are investigated in a one-component atomic gas in the field of resonant laser radiation. This is a continuation of the work in Chermyaninov and Chernyak [“Light-induced phenomena in one-component gas: Pressure anisotropy and change of gas temperature,” Phys. Fluids 32, 017105 (2020)]. An atomic gas located between infinite parallel plates is considered. A traveling electromagnetic wave propagates along the plates, whose frequency is close to that of electron transitions in gas atoms from a ground state to an excited one. Resonant optical radiation stimulates gas pressure anisotropy and a change in its temperature. General expressions are obtained for the longitudinal and transverse changes in gas pressure, as well as for the optical change in its temperature. The kinetic coefficients that determine the magnitude of these phenomena are calculated for large Knudsen numbers (Kn). The results for atomic and molecular gases are compared.

Light-induced phenomena in one-component gas: Pressure anisotropy and change of gas temperature

The phenomena of pressure anisotropy and radiative temperature change in a one-component gas in a field of resonant laser radiation are investigated. This is a continuation of the work by Chermyaninov and Chernyak [“Light-induced phenomena in one-component gas: The transport phenomena,” Phys. Fluids 28, 092007 (2016)]. A model of a limitless gas, and a gas between infinite parallel plates at large Knudsen (Kn ≫ 1) numbers are considered. The mechanisms of these phenomena are discussed. Expressions for the components of the pressure tensor and the change of gas temperature are obtained. Numerical estimates of these effects are provided for the case of the inhomogeneous broadening of the absorption line.

Photoinduced Hund excitons in the breakdown of a two-orbital Mott insulator

We study the photoinduced breakdown of a two-orbital Mott insulator and resulting metallic state. Using time-dependent density matrix renormalization group, we scrutinize the real-time dynamics of the half-filled two-orbital Hubbard model interacting with a resonant radiation field pulse. The breakdown, caused by production of doublon-holon pairs, is enhanced by Hund's exchange, which dynamically activates large orbital fluctuations. The melting of the Mott insulator is accompanied by a high to low spin transition with a concomitant reduction of antiferromagnetic spin fluctuations. Most notably, the overall time response is driven by the photogeneration of excitons with orbital character that are stabilized by Hund's coupling. These unconventional "Hund excitons" correspond to bound spin-singlet orbital-triplet doublon-holon pairs. We study exciton properties such as bandwidth, binding potential, and size within a semiclassical approach. The photometallic state results from a coexistence of Hund excitons and doublon-holon plasma.

Ultrashort Radiation of Biexcitonic Superfluorescence from High-Density Assembly of Semiconductor Quantum Dots

High-density semiconductor quantum dot (QD) assembly is a promising system to generate ultrashort radiation of superfluorescence (SF) which is a cooperative emission of many coherent excited particles induced by an interaction with a resonant radiation field. In this paper, we report the superfluorescent spectra and time profiles of biexcitons in CuCl QDs where a complete population inversion between the biexciton and exciton states was achieved by resonant two-photon excitation of biexcitons. A spontaneous emission at low excitation density changed to SF by increasing the excitation density. For a high excitation density, superfluorescent characteristics, i.e., narrowing of the pulse width and shortening of the delay time, were observed. Furthermore, broadening of the spectral width was observed, resulting from the enhancement of radiative rate of QD assembly. On the other hand, the SF at low temperature changed to an amplified spontaneous emission with the increase in temperature due to the increase in ...

Modelling elliptically polarised free electron lasers

A model of a free electron laser (FEL) operating with an elliptically polarised undulator is presented. The equations describing the FEL interaction, including resonant harmonic radiation fields, are averaged over an undulator period and generate a generalised Bessel function scaling factor, similar to that of planar undulator FEL theory. Comparison between simulations of the averaged model with those of an unaveraged model show very good agreement in the linear regime. Two unexpected results were found. Firstly, an increased coupling to harmonics for elliptical rather than planar polarisarised undulators. Secondly, and thought to be unrelated to the undulator polarisation, a significantly different evolution between the averaged and unaveraged simulations of the harmonic radiation evolution approaching FEL saturation.

Steady-state multipole moments of atoms in a resonant field with elliptical polarization

Steady-state multipole moments of atoms ρK q of the rank K ⩽ 2 are analytically calculated for all closed dipole transitions Jg → Je in a resonant radiation field with arbitrary intensity and arbitrary elliptical polarization. The nonlinear propagation of a monochromatic elliptically polarized wave through a medium consisting of atoms with resonant transition Jg → Je is considered as an application.

Room-temperature proton-hopping transport in rutile-type oxides in the field of resonant laser radiation

A method of decreasing the operating temperature of devices based on proton-hopping transport is considered, which is new in the field of solid-oxide fuel cells. It is shown that the room-temperature rate of proton-hopping transport in rutile-type oxides can be sharply increased in a sample excited by resonant infrared radiation.

The collective Lamb shift in nuclear γ-ray superradiance

The electromagnetic transitions of Mossbauer nuclei provide almost ideal two-level systems to transfer quantum optical concepts into the regime of hard x-rays. If many identical atoms collectively interact with a resonant radiation field, one observes (quantum) optical properties that are strongly different from those of a single atom. The most prominent effect is the broadening of the resonance line known as collective enhancement, resulting from multiple scattering of real photons within the atomic ensemble. On the other hand, the exchange of virtual photons within the ensemble leads to a tiny energy shift of the resonance line, the collective Lamb shift, that remained experimentally elusive for a long time after its prediction. Here we illustrate how highly brilliant synchrotron radiation allows one to prepare superradiant states of excited Mossbauer nuclei, an important condition for observation of the collective Lamb shift.

Secondary Radiation Field Effects for the CEM Spectra

The secondary resonant radiation field and resonant absorption thickness effects on the CEMS (Conversion Electron Mossbauer Spectroscopy) spectra are analyzed for highly enriched resonant targets. It is shown that secondary field effect is important for the thick Fe - α foil enriched in the resonant isotope. Even for the polycrystalline sample traces of the coherent resonant field have been detected as the distortion of lines. Secondary field is discussed in detail. Suitable approximations to treat spectra originating from targets with significant resonant thickness developing secondary field composed of the incoherent and coherent parts are introduced. Finally, the formalism is applied to the high quality spectrum recorded for the enriched iron foil and correlation between contribution due to the secondary field and experimental line shape is investigated.

Large radiation fields from nonlocal interaction between terahertz waves and quantum wells with an applied electric field

The effects of pump intensities and applied electric fields on radiation fields excited by the nonlocal interaction between terahertz waves and AlGaAs/GaAs quantum wells (QWs) are investigated. The numerical results show the resonant radiation fields are very large in the confinement direction, and their spectra and spatial distributions are tunable by the applied electric field. In addition, it is clarified that the second-order and third-order nonlinearities will emerge when the pump intensity reaches 108 and 109 W/m2 orders of magnitude, respectively, and the latter makes the second-harmonic (SH) intensity derivate from the expected square law dependence on the pump intensity, even induces the system into saturation. The maximum SH conversion efficiency is 4.3×10−4. These results are helpful for the accurate observations on the nonlinear optical effects in the QWs by experiment.

Influence of an electric field on the magnetoabsorption in a field of resonant laser radiation

The frequency dependence of the coefficient of interband magnetoabsorption of a weak electromagnetic wave propagating in a constant electric field and in a field of resonant laser radiation at a frequency equal to the cyclotron frequency (infrared magnetic resonance) is calculated. The specific features observed in interband absorption of the electromagnetic wave in a uniform electric field are considered for the case in which the frequency of laser radiation is equal to the confinement frequency in a parabolic quantum well (infrared quantum-well resonance).

Critical size of aerosol particles in the resonance radiation field

The problem of the critical (equilibrium) size of a small aerosol particle (drop) and the critical thickness of a thin liquid film on the particle with account for the resonance radiation effect is considered. Joint influence of heat and resonance effects is discussed.

Steady state of atoms in a resonant field with elliptical polarization

We present a complete set of analytical and invariant expressions for the steady-state density matrix of atoms in a resonant radiation field with arbitrary intensity and polarization. The field drives the closed dipole transition with arbitrary values of the angular momenta $J_{g}$ and $J_{e}$ of the ground and excited state. The steady-state density matrix is expressed in terms of spherical harmonics of a complex direction given by the field polarization vector. The generalization to the case of broad-band radiation is given. We indicate various applications of these results.

Light magnetoabsorption in systems with quantum confinement in the field of resonant laser radiation

Near-gap light magnetoabsorption is investigated in systems with quantum confinement in the presence of IR laser radiation. It is shown that if the frequency of laser radiation is equal to the cyclotron frequency, the magnetoabsorption line shape can be fully determined by the IR radiation intensity. The frequency dependence of interband absorption of a weak electromagnetic wave can be changed significantly in the case where the laser radiation frequency is equal to the quantum-confinement frequency in parabolic quantum wells and the polarization vector is parallel to the confinement axis.

Effect of molecule adsorption on force affecting aerosol particles in resonance radiation field

Effect of molecule adsorption on force affecting aerosol particles in resonance radiation field

Gas pressure on the surface of condensed phase in a resonance radiation field

The influence of resonance radiation on the pressure exerted by gas on the surface of a condensed phase is studied. The effects, which are associated with a change in the recoil pressure of molecules escaping from the surface in a radiation field, are considered. Combined manifestation of thermal and resonance effects is analyzed, as well as the influence of a change in the indicatrix of scattering of the molecules leaving a surface in a radiation field. It is shown that new components of a photophoretic force, that acts on an aerosol particle, can appear in the field of resonance radiation. In such a situation there is a resultant force even in the case of uniform heating of the particle when classical photophoresis does not occur.

Quantum control of non-circular Trojan states in hydrogen

Control of non-circular and non-spreading wave packet states by a resonant radiation field is predicted and numerically confirmed for hydrogen.

Photophoresis of aerosol particles in a resonance radiation field

The additional force exerted by a gas on an aerosol particle on account of the change in recoil momentum of the gas molecules on the surface of the particle in a resonance radiation field is analyzed.