Action Of High-power Laser Radiation Research Articles

Magnetron sputtering system with reactive plasma assisting for deposition of TixZr1-xO2 coating resistant to laser radiation

The magnetron sputtering system with reactive oxygen plasma assisting for deposition of TixZr1-xO2 nanocomposite coatings by sputtering a single Ti-Zr target and the results of study of the stability of these coatings to the action of high-power laser radiation are presented. The periodically repeated sequential processes of applying sputtered material onto a substrate and oxidation of the deposited material have been realized for obtaining the optical coating with resistance to the 960 W/cm2 laser radiation.

Relativistic ponderomotive forces in the field of intense laser radiation

The motion of a relativistic charged particle in the presence of the field of high-power laser radiation represented in the form of a Gaussian beam of arbitrary mode is analyzed. The vector potential of the radiation field is expanded in terms of a small parameter (the ratio of the wavelength to the Gaussian beam waist). A specific feature of averaging with respect to the phases of the high-mode Gaussian beams is demonstrated. The averaged equations for the motion of particle and a general expression for the ponderomotive relativistic force for the circularly polarized radiation are derived. It is demonstrated that relativistic effects suppress the averaged action of high-power laser radiation on the particle.

Photoinduced transparency of a suspension of onion-like carbon nanoparticles

We have observed the phenomenon of photoinduced transparency in a suspension of onion-like carbon (OLC) nanoparticles in N,N-dimethylformamide (DMF) under the action of high-power laser radiation (λ = 1064 nm). The OLC particles were prepared from detonation nanodiamonds (NDs) by means of high-temperature annealing in vacuum and then ultrasonically dispersed in DMF. Upon exposure to laser radiation, the optical density of the suspension significantly decreases in the visible and near-infrared range, but increases in the range of wavelengths below 400 nm.

Tunneling and above-barrier ionization of atoms in a laser radiation field

Calculations are made of the energy and angular distributions of photoelectrons during tunneling ionization of an atom or an ion under the action of high-power laser radiation (for all values of the Keldysh parameter γ). Cases of linear, circular, and elliptic polarizations of the electromagnetic wave are considered. The probability of above-barrier ionization of hydrogen atoms in a low-frequency Open image in new window laser field is calculated. Formulas are given for the momentum spectrum of the electrons when an atomic level is ionized by a general type of alternating electric field (for the case of linear polarization). An analysis is made of tunneling interference in the energy spectrum of the photoelectrons. Analytic approximations are discussed for the asymptotic coefficient Cκ of the atomic wave function at infinity (for s-wave electrons).

Feasibility of experimental identification of the thermophysical mechanism of formation of periodic surface structures

An analysis is made of the results of observations which led to important conclusions on thermophysical mechanisms of formation of periodic surface structures which appeared on germanium under the action of high-power laser radiation.

Motion of a periodic surface microrelief under the action of high-power laser radiation

It was established that the action of high-power laser radiation on the surface of Ge caused a surface shift of the periodic structure formed by such radiation. An explanation was provided of this shift and calculations indicated that for some angles of incidence of the interacting radiation the shift should vanish.

Thermocapillary convection in a liquid under the action of high-power laser radiation

An investigation is made of the structure of hydrodynamic flows which form in a liquid bath as a result of inhomogeneous heating of the free surface of the liquid by laser radiation. It is shown that a liquid flow characterized by Reynolds numbers Re1 may appear when the laser power density is high. The changes in the temperature and vorticity then occur in a narrow layer near the bath walls, whereas outside this boundary layer the flow is isothermal and it is characterized by a constant curl of the velocity. At high Peclet numbers the process of convective heat transfer reduces considerably the temperature drops in the bath compared with the case of a liquid at rest.

Nonlinear photoelectric emission from metals induced by a laser radiation

A review is made of the current status of research on the nonlinear photoelectric emission resulting from the action of high-power laser radiation. The main experimental results are considered and possible theoretical interpretations are discussed. Considerable attention is concentrated on topics investigated recently, such as photoelectric emission in electrolyte solutions; photoelectric emission under the action of ultrashort laser pulses; detailed time, polarization, energy, and some other characteristics of photoelectric emission. Methods and results of calculations of the nonlinear photocurrent from the surfaces of metals are described. Theoretical results obtained by various methods are compared with one another and with the experimental data.

Possible photochemical action of high-power laser radiation on fog droplets

It is shown that fog water droplets may scatter ultraviolet laser radiation as a result of photodissociation of molecules in liquid water. Estimates are obtained of the power of the fourth harmonic of picosecond ruby laser pulses necessary for the conversion of a water droplet of 2-μ radius into a mixture of gases. The quantum yield of hydrogen as a result of photolysis of liquid water is assumed to be 0.022 molecules per photon. The necessary energy density per pulse is ~700 I/cm2.

Thermal action of high-power laser radiation on the surface of a solid

A theoretical analysis is made of the thermal action of high-power laser radiation on the surface of a solid. Temperature and stress fields generated in an irradiated solid are investigated. Dependences of the maximum laser radiation intensities are calculated as a function of the pulse duration. These calculations are made for three states of a reflecting surface corresponding to maximum permissible elastic stress on the surface, plastic flow producing residual stresses, and melting of the surface layer.