KEYWORDS: Diamond, Carbon dioxide lasers, Molecules, Combustion, Emission spectroscopy, Molecular lasers, Gas lasers, Temperature metrology, Chemical vapor deposition, Thin films
Optical emission spectroscopy (OES) measurements were carried out to study premixed C2H4/O2 and C2H4/C2H2/O2
combustion flame for diamond deposition with and without a CO2 laser excitation. Strong emissions from radicals C2
and CH were observed in the visible range in all the OES spectra acquired. By adding a continuous-wave CO2 laser to
irradiate the flame at a wavelength of 10.591 μm, the common CO2 laser wavelength, it was discovered that the emission
intensities of the C2 and CH radicals were increased due to the laser beam induced excitation. OES measurements of the
C2 and CH radicals were performed using different gas combinations and laser powers. The rotational temperatures in
the flame were determined by analyzing the spectra of the R-branch of the A2Δ→X2Π (0, 0) electronic transition near
430 nm (CH band head). Information obtained from the OES spectra, including the emission intensities of the C2 and CH
radicals, the intensity ratios, and the rotational temperatures, was integrated into the study of diamond deposition on
tungsten carbide substrates for mechanism analysis of the laser induced vibrational excitation and laser-assisted diamond
deposition.
Laser-induced breakdown spectroscopy (LIBS) with spatial confinement and LIBS combined with laser-induced fluorescence (LIF) have been investigated to improve the detection sensitivity and selectivity of LIBS. An obvious enhancement in the emission intensity of Al atomic lines was observed when a cylindrical wall was placed to spatially confine the plasma plumes. The maximum enhancement factor for the emission intensity of Al atomic lines was measured to be around 10. Assuming local thermodynamic equilibrium conditions, the plasma temperatures are estimated to be in the range from 4000 to 5800 K. It shows that the plasma temperature increased by around 1000 K when the cylindrical confinement was applied. Fast imaging of the laser-induced Al plasmas shows that the plasmas were compressed into a smaller volume with a pipe presented. LIBS-LIF has been investigated to overcome the matrix effects in LIBS for the detection of trace uranium in solids. A wavelength-tunable laser with an optical parametric oscillator was used to resonantly excite the uranium atoms and ions within the plasma plumes generated by a Q-switched Nd:YAG laser. Both atomic and ionic lines can be selected to detect their fluorescence lines. A uranium concentration of 462 ppm in a glass sample can be detected using this technique at an excitation wavelength of 385.96 nm for resonant excitation of U II and a fluorescence line wavelength of 409.01 nm from U II. The mechanism of spatial confinement effects and the influence of relevant operational parameters of LIBS-LIF are discussed.
Pulsed-laser deposition (PLD) is a versatile technique for thin film deposition. The generation and propagation of laser-induced
plasmas have been extensively studied. Other plasma sources have been combined with PLD to improve the film
qualities. The knowledge about the interactions between the laser-induced plasmas and additional plasmas and their
effects on film growth is still limited. We have investigated the optical emission spectra from the interaction region of
low-pressure ECR microwave plasmas and pulsed-laser-induced plasmas. In this region, the spatial and temporal
distributions of the laser-ablated species were altered while very few collisions were expected in the ambient gas due to
the low pressure. The results were compared with those with laser ablation or ECR microwave discharge along. The
mechanisms and effects of the interactions were discussed.
CO2 gas dissociation through optical and plasma collision breakdown was investigated by optical emission spectroscopy (OES), using an Andor Mechelle monochromator with an iStar intensified charge coupled device (ICCD). A pulsed Nd:YAG laser was used to provide energy for the gas breakdown processes. The evolution of the luminous plasmas was examined by time-resolved optical spectroscopy. Emission lines of carbon and oxygen species, such as atomic C (I), ionic C (II) and atomic O (I), were observed to understand the process of CO2 dissociation. Effects of background gas pressure on plasma propagation in the experiments were studied. Some emission lines could be obviously distinguished, indicating that the emitting species had different behaviors in the evolution. They were frequently ionized and excited after the laser irradiation.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.