RESUMO
The stimulated emission (SE) in aluminum laser-induced plasma pumped in resonance with the 3s23p-3s24s aluminum transition at 266.04 nm is investigated experimentally. It is shown that the population inversion between the 3s23p and 3s24s states can be created by weak pumping at several microjoule to millijoule pulse energies and result in high gain. The intensity of the SE at 396.15 nm is related to the number density of Al atoms via absorption measurements. It is found that the SE in forward and backward directions with respect to the pumping laser is different in terms of the line shape and intensity that is attributed to inhomogeneity in a gain coefficient across the plasma plume.
RESUMO
The stimulated emission (SE) in aluminum laser-induced plasma pumped in resonance with the 3s23p-3s24s aluminum transition at 266.04 nm is modeled. A collisional-radiative plasma model based on kinetic equations is proposed to explain the creation of the population inversion and lasing. The model predicts fast depopulation of the ground 3s23p state by the absorption of resonant laser light at 266 nm and very fast population of the excited 3s24s state by the cascade transitions from the laser-pumped level, which is driven optically and by collisions. The SE of the 3s23p-3s24s transition at 396.15 nm is studied and possible SE at 1.3 and 2.1 µm is predicted. It is confirmed by calculations that the population inversion between the 3s23p and 3s24s states can be created by weak pumping at several microjoule-millijoule pulse energies and results in high gain.
RESUMO
We propose combining laser-induced breakdown spectroscopy (LIBS) with molecular laser-induced fluorescence (MLIF) with resulting plasma-borne molecules as a means of studying laser-induced plasma (LIP). Examples of this method with LIP-created Al, Si, and B monoxides are presented. Applicability of the LIBS-MLIF method for elemental and isotope analysis is demonstrated.
RESUMO
From its inception, laser-induced breakdown spectroscopy (LIBS) has been recognized as a prospective tool for online process control. Nevertheless, it took considerable time and effort to transform this potential opportunity into application in a working industrial system, such as the mining industry, under real-life conditions and a 24/7 operating mode. There were three main attributes of LIBS to prove: its advantage over other online techniques, mainly prompt gamma neutron activation analysis and X-ray fluorescence; its ability to give relevant data despite its surface but not volume analytical abilities; and its ability to be sufficiently accurate for online process control needs. Comparison of the quantitative results gained from industrial installations of an LIBS analyzer with results of conventional analytical methods and, most importantly, the substantial improvement of the technological process effectiveness proved that LIBS is in fact an excellent technique for online process control in the mining industry.
RESUMO
We studied the confocal double-pulse laser-induced plasma in the very beginning of its life. It was found that the second laser pulse fired 0.7 to 5 µs after the first pulse produces plasma which, during the first 0 to 20 ns, resembles solar configuration. There is a very hot and compact plasma core that radiates a broad continuum spectrum and a much larger and cooler outer shell. The light from the hot core passes through the cold outer shell and is partly absorbed by atoms and ions that are in ground (or close to ground) states. This produces absorption lines that are similar to Fraunhofer lines observed in the sun spectrum. The possibility to use these absorption lines for new direct and calibration free laser-induced breakdown spectroscopy analytical applications, both in laboratory and industrial conditions, is proved.
RESUMO
The absorption and the kinetics of the emission in the mid-infrared (mid-IR) were investigated in AgCl(x)Br(1-x) crystals doped with Dy(3+) ions. Strong emission bands were detected at 3, 4.4, and 5.5 µm and attributed to the (6)H(13/2)â(6)H(15/2), (6)H(11/2)â(6)H(13/2), and (6)F(11/2)+(6)H(9/2)â(6)H(11/2) transitions. Various optical parameters were calculated for the Dy(3+) doped crystals, using the Judd-Ofelt approximation and the rate equations. The measured results and the calculated parameters indicate that these doped crystals could be used for the development of mid-IR solid-state lasers or mid-IR fiber lasers.
RESUMO
The luminescence of AgBr, AgCl, and AgClBr crystals and fibers doped with Pr3+ ions was investigated in the middle-infrared spectral range. We measured the absorption, emission, and kinetic parameters over a broad temperature range. Strong luminescence in the spectral range 4-5.5 microm was observed for the first time to our knowledge in silver halide crystals and fibers at room temperature. No noticeable differences were observed between the crystals and the fibers. We calculated various optical parameters for Pr:AgBr and Pr:AgCl crystals, using the Judd-Ofelt approximation. Both the measured results and the calculated parameters indicate that these doped crystals and fibers would be good candidates for the fabrication of mid-IR solid-state lasers or fiber lasers.
RESUMO
Diffraction phase gratings are formed on samples of crystalline silver halide by exposing them through a mask to 353-nm laser light followed by chemical processing. The exposure and photographic development processes generate metallic silver strips on the sample surface. The fixing process removes the silver strips, leaving grooves on the surface as deep as 1.1 microm. Gratings of 100-microm period are thus formed. The groove depth is determined by optical methods and is confirmed by atomic force microscopy. This method can be used to form diffractive optical elements on IR transmitting fibers and waveguides as well as on crystals.
