The process of laser ablation of fused and crystal silica and natural silicates induced by pulsed CO2 laser irradiation (total pulse duration of 35 μs, laser pulse rise time of 0.1 μs, pulse energy of 10 J) has been studied. By action of focused laser radiation at the surface of samples the appearance of erosion plume at the irradiated surface take place. For study of ablation regimes the frame image of laser induced plume by use of high speed photography method with 2 microsecond expose of each frame have been made. It has been observed the formation of two different type of laser plume during laser pulse action. First type plume represents a long narrow plume with the onset close to start of laser pulse. The maximal length of this plume is about of 20 millimeter. The second type of plume represents a conical plume with the onset, which is late from laser pulse start for a few microsecond. The first type plume expands in to laser beam direction. The second type plume expands normal to the surface. The velocity of laser plume particles by means of measurements of moment transferred into samples during laser pulse action has been measured. It has been obtained, that value of this velocity varies in region of (l÷3)103 m/s in dependence of laser fluency value. The appearance of first time plume have a threshold which equal to 0.30 kJ/cm2 whereas the appearance of second type plume have not a such threshold and may take place at low laser fluency. We believe, that the first type plume connects with the selective ablation of SimOn complexes whereas second type plume connects with the thermal heating caused by dissipation of laser energy in to system of low frequency acoustics phonons.
The laser ablation of fused and crystal silica and natural silicates induced by pulsed CO2 laser irradiation (total pulse time of 35 μs, pulse increase time of 0,1 μs, pulse energy of 10 J) has been studied. By action of focused laser radiation at the surface of samples the appearance of erosion plume at the irradiated surface take place. For study of ablation regimes the frame image of laser induced plume by use of high speed photography method with 2 microsecond expose of each frame have been made. It has been observed the formation of two different type of laser plume during laser pulse action. First type plume represents a long narrow plume with the onset close to start of laser pulse. The maximal length of this plume is about of 20 millimeter. The second type of plume represents a conical plume with the onset, which is late from laser pulse start for a few microsecond. The first type plume expands in to laser beam direction. The second type plume expands normal to the surface. The velocity of laser plume particles by means of measurements of moment transferred into samples during laser pulse action has been measured. It has been obtained, that value of this velocity varies in region of 1-3•103 m/s in dependence of laser fluency value. The appearance of first time plume have a threshold which equal to 0,15 kJ/cm2 whereas the appearance of second type plume have not a such threshold and may take place at low laser fluency. We believe, that the first type plume connects with the selective ablation of SimOn complexes whereas second type plume connects with the thermal heating caused by dissipation of laser energy in to system of low frequency acoustics phonons.
Under the impact of powerful laser radiation in semiconductors occur processes, essentially change their properties. For instance, in (1) observed annealing of ion- implanted silicon, vastly improving quality of semiconductor devices, made form it. In (2) was observed laser-stimulated diffusion of impurity atoms on the direction to surface, and in (3) on the contrary, deep into the semiconductor. In (4) an increase of velocity of chemical reactions on semiconductor surface under the influence of laser radiation was observed. In the present work spectra of radiation reflection of low power continuous CO2-laser from the surface of monocrystals of semiconductor AII BVI compounds previously irradiated by powerful pulses of CO2 laser were investigated.
Experiments on laser-rock-fluid interaction have been carried out by using pulsed CO and CO2 lasers which irradiated rocks typical for oil field: sandstone, limestone, shale and granite. Energy fluence and laser intensity on rock surface were up to 1.0 kJ/cm2 and 107W/cm2, respectively. The dependencies of specific energy consumption (i.e. energy per volume needed for rock excavation) on energy fluence, the number of pulses, saturated fluid, rock material and irradiation conditions have been obtained for various rock samples. The dependencies of momentum transferred to the rock on energy fluence for dry rocks and rocks with surface saturated by water or mineral oil have been measured. High-speed photography procedure has been used for analyzing laser plasma plume formation on a rock surface. Infrared spectra of reflectivity and absorption of rocks before and after irradiation have been measured.
Experiments on laser-rock-fluid interactions have been carried out by using pulsed CO and CO2 lasers which irradiated rocks typical for oil field: sandstone, limestone, shale and granite. Energy fluence and laser intensity on rock surface were up to 1.0 kJ/cm2 and 107 W/cm2, respectively. The dependencies of specific energy consumption (i.e. energy per volume needed for rock excavation) on energy fluence, the number of pulses, saturated fluid, rock material and irradiation conditions have been obtained for various rock samples. The dependencies of momentum transferred to the rock on energy fluence for dry rocks and rocks with surface saturated by water or mineral oil have been measured. High-speed photography procedure has been used for analyzing laser plasma plume formation on a rock surface. Infrared spectra of reflectivity and absorption of rocks before and after irradiation have been measured.
The photochemical transformations at the surface of single crystal zircon (ZrSiO4) induced by the action of continuous CO2 laser radiation (105 - 106 W/cm2) has been investigated. It has been found that the action of infrared laser radiation on the surface of zircon results in a selective sublimation of silicon oxides as well as in a change of electronic state of zirconium atoms included in the silicate matrix. The change of electronic state of zirconium atoms is confirmed by the change of the relation of K- and L-component intensity in X-ray emission spectra recorded by an X-ray microprobe analysis of irradiated samples. This change is connected with the decrease of a shielding of inside electrons and the delocalization of electron density into position of defects. The appearance of nonequilibrium electronic states of zirconium atoms is accompanied with the creation of the defect metallic clusters, in which the part of oxygen atoms is removed by laser sublimation of silicon-oxygen groups.
The action of pulsed CO2 laser (power density of 107 W/cm2, length of pulse 200 nsec) on the surface of the synthetic single crystal quartz has been investigated. The experiments have shown that the stable hole burning in infrared reflection spectra just at the frequency of laser action was appeared. The hole with a half width of 4 cm-1 was burned in the reflection spectra of irradiated samples. The photoluminescence and electron spin resonance investigations have shown, that this hole burning is connected with destruction of Si-O bonds and with appearance of a several different defects centers.
The action of CO2 laser (power density of 103 - 106 W/cm2) on silicates has been investigated. Spectroscopic, chemical and x-ray analysis of sublimates and irradiated zone made it possible to establish, that by laser action on these matters the selective excitation of localized vibrational mode up to breaking of covalent bonds with the selective sublimation of Si-O groups take place.
The action of CO2 laser (power density of 103 - 106 W/cm2) on silicates has been investigated. Spectroscopic and chemical analysis of sublimates and irradiated zone made it possible to establish that by laser action on these matters the selective excitation of localized vibrational mode up to breaking of covalent bonds with the selective sublimation of Si-0 groups take place.
An investigation of the magnetic properties of iron-contained quartzite irradiated by CO2 laser (power density of 103 - 105 W/cm2) has been made. It has been found that the decrease of the matters specific magnetization by the increase of irradiation intensity takes place. This decrease is caused by structure transformations in crystalline lattice, leading to a decrease of iron ion content in ferromagnetic phase (magnetite) and to an increase of ion content in paramagnetic glass phase.
The effect of CO2 laser focised radiation (the wavelength of
1O.6,ii't , power density of io 10 VJ/crnt) quartz by method of
electron spin resonance (ESR) has been investigated. ESR spectra of
crystallic powder (particle size of iO..iOO,M) befor and after laser
irradiation at the room temperature have been registrated. Irradia-..
tion of 1O.6,Mlead to appearance of intensive wide asymmetric line
( '& H - 90 iiiT , g '-' 2 , 5 ) and more slight narrow line on the right side
of wide line with g=1.943. Appearance of wide line with g2.5 is
connected with activisation of paramagnetic centra on the surface
of desorienting powder particles. More narrow line with g=1.943 is
due to distru.ction of bonds inside of network in region of laser
radiation penetration depht.
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