CO2 laser beam

Submicron pSiC powder by reacting silane and acetylene in a 10-50 W continuous-wave CO2 laser beam.P" l... 

Spjut and his associates heated levitated microparticles and measured their temperatures radiometrically. They levitated a microparticle in a bihyperbol-oidal quadrupole, and they irradiated the particle from opposite sides by splitting a cw CO2 laser beam and directing the beams by means of mirrors to illuminate the particle symmetrically (Spjut et al., 1987). The particle temperature was measured by multiple-color pyrometry (Spjut, 1987 Spjut and Bolsaitis, 1987) using narrow-band infrared detectors. The temperature... 

Figure 7. Top. (M-H)- ion of sucrose formed by desorption with pulsed CO2 laser beam. Bottom. Dissociation upon irradiation with the cw CO2 laser. Experimental conditions are same as in the top spectrum.

Laser vaporization reactor. At LTT-Erlangen, first investigations with other nanomaterials have been carried out in cooperation with the group of Staupendahl at the University of Jena in a laser vaporization reactor (LVR) (Staupendahl, 2003). The basic principle of this reactor is dispersing raw material by a fountain into the CO2 laser beams, in which particles are vaporized and nanoparticles are formed by the subsequent condensation. As the LII measurement volume was located slightly above the vaporization zone, it was not possible to prevent coarse structures of material to occur inside the measurement volume (Figure 20). 

Helisys Inc., Torrence. CA. USA Laminated Object Manufacturing (LOM) Self-adhesive paper and plastic films cutting of the films layer by layer with a CO2 laser beam... 

Figure 6. Radial temperature distribution in the (Mg, Fe)Si03 sample heated with a defocused CO2 laser beam at 29 GPa. Temperatures were measured (symbols) in 4 pm steps with a spatial resolution of 2.5 pm. In the central region of the heated area (with about 30 pm in diameter) the temperature gradients are below 10Kpm. After [21].

Considerable progress has been achieved in recent years on improving the optical properties of CVD diamond and in making this material available in large sizes and with reproducible and consistent properties [4,5,35] so that its use in actual laser systems has become a practical reality [48]. This section reviews the technical issues relevant to the performance of windows for high power lasers comparing the specific case of CVD diamond and ZnSe for the transmission of CO2 laser beams. 

As a general rule it can be assumed that the lensing effect can be neglected if the difference in A is smaller than X/10 [51], or 1 pm for a CO2 laser beam. As shown in... 

The decomposition of gaseous PH3 in a focused CO2 laser beam is not an IR multiphoton decomposition, but due to a dielectric breakdown. The decomposition arises from the interaction of the generated free electrons with PH3. The decomposition is accompanied by a visible chemiluminescence stemming from formed PH2, PH, H2, H, and probably HJ [4]. 

Fig. 5.118. Generation of tunable FIR radiation by frequency mixing of two CO2 laser beams with a microwave in a MIM diode...

The radial dimensions of the CO2 laser beam are of importance, considering possible temperature influences on plant tissues. In experiments, care has been taken to avoid e.g. heating and burning. In the wings of the Gaussian beam profile there is still a lot of laser power available. Remember that one has 100 W in a beam of 0.28 mm waist. In a simple experiment, we placed a thermocouple inside a tomato just beneath the epidermis, which showed that at least a distance of 1.5 mm has to be introduced between the center of the pump beam and the plant tissue, e.g. tomato surface. At this distance a temperature rise of 1 °C is then observed. In all our experiments we chose a distance of 1.5 mm. The temperature rise due to absorption of ambient gases (CO2 and H2O) is of the order of 10 to 100 mK at the center of the CO2 laser beam. This temperature rise influences the tissue negligibly. 

CO2 and Twin CO2. A CO2 laser beam cannot penetrate copper foil nnless the foil is very thin, less than 5 pm, and the surface is treated to be dark to absorb the CO2 laser beam (this process is called CO2 laser direct drilling and will be treated later). 

In the case of using an articulated arm to propagate a CO2 laser beam that is in the infrared (invisible), a co-propagating visible beam (usually a red beam from a He-Ne laser or a diode laser) is used as an aiming beam (Prasad, 2003). 

Fig. 1 shows the experimental setup used in this study. To prevent sound from entering from outside, the irradiation area was enclosed in a sound-proof box. The CW CO2 laser beam (power 50 W wavelength 10.6 pm) was focused onto the sample surface by a ZnSe lens (focal length 10 cm). The laser irradiation was 80 ms it was controlled using a mechanical shutter. 

One potential, and perhaps unexpected, application of conductive polymers is for the definition of conductive tracks on printed circuit boards. Rubner et al. [98] exploited the thermal properties of PPS to enable the selective introduction of conductivity by doping. By using a heat gun or a CO2 laser beam and a suitable masking procedure, the PPS could be made to undergo a premelting crystallization at 150 C, such that there... 

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