D. V. Novitsky | Searcharxiv

arXiv2023

Density of states effects on emission and scattering of photons in plasmas

Plasma supports electromagnetic waves propagation for frequencies higher than plasma frequency but features dielectric permittivity less than 1. This property leads to photon density of states (DOS) lower than in vacuum and should result in subnatural spectral linewidths, sub-Planckian spectrum of thermal radiation, and sub-Rayleigh scattering as well as in lower inelastic photon scattering including Raman scattering. Lamb shift will be altered as well though the decisive contribution from high-energy modes in this case makes the photon DOS effect rather small since plasma DOS converges with the vacuum one in the limit of infinite frequencies. We emphasize the basic character of all these phenomena though absolute values of corrections in many real experiments may appear to be small as compared to other factors. We found that dissipative losses make possible DOS effects smaller though not vanishing and additionally bring about indefinite growth of DOS in the low-frequency limit.

physics.optics↗

arXiv2021

Transportation dynamics of dielectric particles with the gradient forces in the field of orthogonal standing laser waves

We develop the theory of transportation and localization of a transparent dielectric spherical particle with the gradient forces in the interference field of orthogonally directed standing laser waves $E_z (\cos kz)$ and $E_x (\cos kx)$. It is shown that, when the waves $E_z$ and $E_x$ are coherent, the interference radiation field contains two harmonic components with the periods $Λ_0=π/k$ and $Λ_Δ=π/(k \sin (π/4))$. The amplitudes of the gradient force components depend on the ratio of the particle radius $R$ to the modulation periods due to inhomogeneity of radiation in the particle volume and are given by the Bessel functions $J_{3/2} (2 πR/Λ_0)$ and $J_{3/2} (2 πR/Λ_Δ)$. We find the critical particle radii $R_0$ and $R_Δ=\sqrt{2} R_0$ defined by the Bessel functions zeros and corresponding to the vanishing components of the gradient forces. In particular, for the radiation with the wavelength $λ_0=1.064$ μm and a particle in water, the smallest critical radii are $R_0=0.286$ $μ$m and $0.492$ μm and $R_Δ=0.404$ $μ$m and $0.696$ $μ$m, respectively. For a number of special cases, we obtain the analytical solutions of the Newton equations and the particle trajectories that depend on the ratio of wave intensities and the particle radius. The results can be used to study the dynamics of the "optical assembly" of a two-dimensional particles matrix which behaves as a molecular crystal.

physics.optics↗