V. D. Dubrov

Spatial structure of focused beams in high-power fiber and CO 2 lasers and peculiarities of their application in cutting

The requirements for quality parameters in radiation of different wavelength (i.e. CO2 lasers and fiber lasers) have been defined so as to perform efficient oxygen-free gas laser cutting of large-thickness samples. The main channels of consumption of radiation power in the cutting process have been considered. It is noted that focused beam divergence not only decreases the cutting speed, but also causes cutting quality deterioration.

Turbulent flow structure of FAF CO2 laser active medium at nonuniform temperature and heat generation

The isobaric fluctuations of temperature and density, attending with turbulent adiabatic fluctuations of velocity, have been evaluated under spatial non-uniformity of temperature and at heat generation in the incompressible flow. The character of their quantity dependence on spatial scale has been revealed. It has been shown that the temperature gradient and specific power of heat generation strongly affect the isobaric fluctuations of temperature.

Diagnostics of turbulent flow parmeters of active mixture in fast axial flow CO2 laser

The characteristics of turbulent flow of laser mixture in high-power industrial CO2 lasers with fast axial flow have an influence on energy parameters of laser beam. In particular the transverse size of DC discharge and discharge stability depend on coefficient of turbulent diffusion. Moreover, turbulent pulsations cause small-scale optical inhomogeneities in the active medium. By the method of intra-resonator four-wave mixing in the active mixture of industrial CO2 laser with fast axial flow the coefficient of turbulent diffusion was determined. The nonlinearity of gain coefficient was used, and dissipation of amplitude diffraction grating due to turbulent diffusion was taken into consideration.

Influence of nonuniform heat-releasing on optical inhomogeneities of active medium turbulent flow in high power CO 2 laser

The enhancement of optical inhomogeneities of active medium of high-power fast-axial flow CO2 laser is coupled with increasing of the isobaric fluctuations of temperature and density in turbulent flow due to nonuniform heat-releasing.

The determination of transverse pulsations of turbulent flow velocity in fast-axial flow CO2 laser by phase-conjugation method

The scheme of intracavity four-wave mixing is used to measure the spectrum of turbulent pulsation of velocity of ative-medium flow in fast-axial flow CO2 laser. The coefficient of transverse turbulent diffusion and viscous size of turbulent pulsations are also obtained.

The investigation of quality of active medium of FAF RF CO2 laser by luminescent method

The luminescent method was used to measure the spectrum of turbulent pulsations of gas density in fast- axial flow CO2 laser with radio-frequency discharge input. It is shown that gas density pulsations increase through gas discharge along gas flow axes. In continuous-wave fast-axial flow (FAF) CO2 laser there is subsidiary deterioration of quality of active medium due to intrinsic turbulence intensified by gas discharge energy input.

Gas laser cutting of metal with oxygen concentration control in assist gas mixture

At the present time the methods of the gas assisted laser cutting (GALC) of the different steels (alloyed and non-alloyed) and also of non-ferrous metals, such as Al and Ti, using one of the inert gases (nitrogen, argon, helium) or the active gas (oxygen) or air as assist gas are widely spread. However these cutting methods have the series of essential shortcomings. Heaving performed the theoretical and practical investigations of the mentioned methods we concluded that the great interest is the use of mixtures containing inert gases and oxygen with controlled concentration. The application of such assist gas mixtures permits the laser cutting velocity to be increased as against the use of pure inert gas. The chose of optimal oxygen concentration leads to reduction of expensive gases consumption and makes the cutting process cheaper.

The determination of a turbulent parameters of active-medium flow of a CO 2 laser by method of intracavity four-wave mixing

The degenerate intra-cavity four-wave mixing on nonlinearity of gain of active medium of cw CO2 laser was used for determination of turbulent parameter of active medium flow.

Influence of external pressure and gas type on mechanism and velocity of metal punching with Nd:YAG-laser pulses

The high-power laser beam interaction with the surface of metals (W, Fe, Ti, stainless steel) has been studied under high external pressures of the inert (Ar) and active (O2) gases. The velocities of punching the samples have been measured at laser pulse power densities I equals 0.5 multiplied by 106 - 107 W/cm2 in the beam revealed in punching velocities depending on the type of external gas. The dynamics of variations in the shape of high-power laser pulse reflected from the surface (W, Fe, Ti) has been studied.

Heterodyne diagnostics by Doppler signal of backscattering of near-surface flows induced by intense laser radiation

A procedure of operational inspection of laser technological processes has been suggested that is based on measuring spectral properties of Doppler signal of backscattering from the interaction region by optical heterodyne technique. The technique enables us to obtain the qualitative and quantitative information on hydrodynamic flows in reactor. The measurements have been performed with about 1 kW/cm2 beam intensity of continuous-wave carbon- dioxide laser at the surface of a number of condensed substances by monostatic scheme of interaction.