Low-temperature laser-stimulated controllable generation of micro-bubbles in a water suspension of absorptive colloid particles.

A method is described for the generation of micrometer-sized vapor-gas bubbles in a water suspension containing absorptive pigment nanoparticles. The diluted suspension (mean interparticle distance 20 μm) absorbs the continuous laser radiation (wavelength 808 nm), and each particle in the best illuminated volume (~10 × 10 × 200 μm) serves as a bubble-nucleation center. The suspension heating is inessential (several degrees above the room temperature) and the bubbles are formed mainly of the air gases dissolved in water.

Influence of evanescent wave on birefringent microplates.

Mechanical action caused by the optical forces connected with the canonical momentum density associated with the local wavevector or Belinfante's spin angular momentum is experimentally verified. The helicity-dependent and the helicity-independent forces determined by spin momenta of different nature open attractive prospects for the use of optical structures for manipulating minute quantities of matter of importance in nanophysics, nanooptics and nanotechnologies, precision chemistry and pharmacology and in numerous other areas. Investigations in this area reveal new, extraordinary manifestations of optical forces, including the helicity-independent force caused by the transverse helicity-independent spin or vertical spin of a diagonally polarized wave, which was not observed and exploited up to recently.

Controllable generation and manipulation of micro-bubbles in water with absorptive colloid particles by CW laser radiation.

Micrometer-sized vapor-gas bubbles are formed due to local heating of a water suspension containing absorptive pigment particles of 100 nm diameter. The heating is performed by CW near-infrared (980 nm) laser radiation with controllable power, focused into a 100 μm spot within a 2 mm suspension layer. By changing the laser power, four regimes are realized: (1) bubble generation; (2) stable growth of the existing bubbles; (3) stationary existence of the bubbles and (4) the bubbles' shrinkage and collapse.

Measurement of small light absorption in microparticles by means of optically induced rotation.

The absorption parameters of micro-particles have been associated with the induced spin exerted upon the particle, when embedded in a circularly polarized coherent field. The induced rotational speed is theoretically analyzed, showing the influence of the beam parameters, the parameters of the particle and the tribological parameters of the surrounding fluid. The theoretical findings have been adequately confirmed in experiments.

Cement hydration investigation by method of piezoelectric photoacoustics.

The piezoelectric photoacoustics application possibility for polycrystalline structure formation has been considered. The accent was on research and transient modeling with pulse laser irradiation. A mathematical model for the given setup with a single laser impulse was developed.