Parametric instabilties of short and ultra-intense laser pulses in a plasma

Parametric instabilities in laser-plasma interactions are investigated in the ultrarelativistic regime, including the leading-order term of the Landau-Lifshitz radiation reaction equation. After a detailed exploration to the theory of parametric instabilities, the effects of the radiation reaction force on the growth rate are discussed by comparing to the results without radiation reaction force. The radiation reaction force leads to merging of the two Raman branches and also excites new modes, e.g. the so-called quasi-modes. Furthermore the radiation reaction force increases the endurance of the short wavelength perturbations. Increased endurence affects the quality of the laser pulse shape, which is important particularly for experiments, which require a precisely-shaped laser pulse

Attractive Optical Forces from Blackbody Radiation

Blackbody radiation around hot objects induces ac Stark shifts of the energy levels of nearby atoms and molecules. These shifts are roughly proportional to the fourth power of the temperature and induce a force decaying with the third power of the distance from the object. We explicitly calculate the resulting attractive blackbody optical dipole force for ground state hydrogen atoms. Surprisingly, this force can surpass the repulsive radiation pressure and actually pull the atoms against the radiation energy flow towards the surface with a force stronger than gravity. We exemplify the dominance of the "blackbody force" over gravity for hydrogen in a cloud of hot dust particles. This overlooked force appears relevant in various astrophysical scenarios, in particular, since analogous results hold for a wide class of other broadband radiation sources

Dynamic radiation force of acoustic waves on solid elastic spheres

The present study concerns the dynamic radiation force on solid elastic spheres exerted by a plane wave with two frequencies (bichromatic wave) considering the nonlinearity of the fluid. Our approach is based on solving the wave scattering for the sphere in the quasilinear approximation within the preshock wave range. The dynamic radiation force is then obtained by integrating the component of the momentum flux tensor at the difference of the primary frequencies over the boundary of the sphere. Results reveal that effects of the nonlinearity of the fluid plays a major role in dynamic radiation force leading it to a parametric amplification regime. The developed theory is used to calculate the dynamic radiation force on three different solid spheres (aluminium, silver, and tungsten). Resonances are observed in the spectrum of the force on the spheres. They have larger amplitude and better shape than resonances present in static radiation force.Comment: 9 pages, 4 figures, to appear in Physical Review