scholarly journals IR Laser-Induced Changes to L-adrenaline-D-hydrogentartrate Incorporated in KBr Matrices

2002 ◽  
Vol 20 (2-4) ◽  
pp. 89-98
Author(s):  
Tatijana S. Jovanovic ◽  
Milica R. Bogavac ◽  
Bojan B. Radak ◽  
Milan S. Trtica
Keyword(s):  
Carbon Dioxide ◽  
Energy Density ◽  
Laser Energy ◽  
Laser Pulses ◽  
Laser Energy Density ◽  
Cooh Group ◽  
Temporal Shape ◽  
Ir Laser ◽  
Out Of Plane ◽  
Induced Changes

Changes in the pharmaceutical L-adrenaline-D-hydrogentartrate, incorporated in KBr matrices, induced by a pulsed carbon-dioxide Transversely Excited Atmospheric (TEA) laser, were observed. Modifications of the sample were monitored via infrared spectra. Special attention was devoted to the dependence of the sample changes on the laser energy density used. The irradiation of the pharmaceutical has been performed with two laser lines at wavelengths of about 10.6 µm. The laser lines coincide well with the absorption band of the pharmaceutical, which is assigned to the ring vibrations/out-of-plane OH deformation vibrations, within the carboxyl (COOH) group of L-adrenaline-D-hydrogentartrate. Laser energy densities of 1.20 and 1.70 J/cm2 modified the pharmaceutical/compound. It was found that this modification is in essence a thermal effect. The level of change showed a dependence on the laser energy density, number of accumulated laser pulses and temporal shape of the pulse.

Low Temperature Laser-Doping Process Using PSG and BSG Films for Poly-Si TFTs

2000 ◽  
Vol 621 ◽  
Author(s):  
Cheon-Hong Kim ◽  
Sang-Hoon Jung ◽  
Jae-Hong Jeon ◽  
Min-Koo Han
Keyword(s):  
Energy Density ◽  
Low Temperature ◽  
Sheet Resistance ◽  
Laser Energy ◽  
Surface Concentration ◽  
Laser Pulses ◽  
Laser Energy Density ◽  
Silicon Thin Film ◽  
Laser Doping ◽  
Si Films

ABSTRACTA simple low-temperature excimer-laser doping process employing phosphosilicate glass (PSG) and borosilicate glass (BSG) films as dopant sources is proposed in order to form source and drain regions for polycrystalline silicon thin film transistors (poly-Si TFTs). We have successfully controlled sheet resistance and dopant depth profile of doped poly-Si films by varying PH3/SiH4 flow ratio, laser energy density and the number of laser pulses. The penetration depth and the surface concentration of dopants were increased with increasing laser energy density and the number of laser pulses. The minimum sheet resistance of 450ω/ for phosphorus (P) doping and 1100ω/ for boron (B) doping were successfully obtained. Our experimental results show that the proposed laser-doping process is suitable for source/drain formation of poly-Si TFTs.

Raman Measurements on Graphite Modified by High Power Laser Irradiation

1984 ◽  
Vol 35 ◽  
Author(s):  
J. Steinbeck ◽  
G. Braunstein ◽  
M.S. Dresselhaus ◽  
B.S. Elman ◽  
T. Venkatesan
Keyword(s):  
Energy Density ◽  
Laser Pulse ◽  
Laser Irradiation ◽  
High Power ◽  
Laser Energy ◽  
Laser Pulses ◽  
Laser Energy Density ◽  
High Power Laser ◽  
Power Laser ◽  
Raman Microprobe

AbstractThe behavior of highly anisotropic materials under short pulses of high power laser irradiation has been studied by irradiating highly oriented pyrolytic graphite (HOPG) with 30 nsec Ruby-laser pulses with energy densities between 0.1 and 5.0J/cm2. Raman spectroscopy has been used to investigate the laser-induced modifications to the crystalline structure as a function of laser energy density of the laser pulse. A Raman microprobe was used to investigate the spatial variations of these near-surface regions. The irradiation of HOPG with energy densities above ~ 0.6J/cm2 leads to the appearance of the ~ 1360 cm-1 disorder-induced line in the first order Raman spectrum. The intensity of the ~ 1360cm-1 line increases with increasing laser energy density. As the energy density of the laser pulse reaches about 1.0J/cm2, the ~ 1360cm-1 line and the ~ 1580cm-1 Raman-allowed mode broaden and coalesce into a broad asymmetric band, indicating the formation of a highly disordered region, consistent with RBS-channeling measurements. However, as the laser energy density of the laser pulses is further increased above 3.0J/cm2, the two Raman lines narrow and can again be resolved suggesting laser-induced crystallization. The Raman results are consistent with high resolution electron microscopy observations showing the formation of randomly oriented crystallites. Raman Microprobe spectra revealed three separate regions of behavior: (i) an outer unirradiated region where the material appears HOPG-like with a thin layer of material coating the surface, (ii) an inner irradiated region where the structure is uniform, but disordered, and (iii) an intermediate region between the other regions where the structure is highly disordered. The changes in structure of the inner region are consistent with the behavior observed with RBS and conventional Raman spectra. The identification of an amorphous carbon-like layer on the outer region is consistent with a large thermomechanical stress at the graphite surface, introduced by the high power laser pulse, and known to occur in metals.

Comparison of Carbon Dioxide and Neodymium: Yttrium-Aluminum-Garnet Lasers in Surgery of the Inferior Turbinate

1997 ◽  
Vol 106 (12) ◽  
pp. 1036-1042 ◽  
Author(s):  
Burkard M. Lippert ◽  
Jochen A. Werner
Keyword(s):  
Carbon Dioxide ◽  
Energy Density ◽  
Yttrium Aluminum Garnet ◽  
Laser Energy ◽  
Inferior Turbinate ◽  
Long Term Results ◽  
Laser Energy Density ◽  
Laser Technique ◽  
Yag Laser

At the Department of Otorhinolaryngology—Head and Neck Surgery of the University of Kiel, 533 patients with hyperplastic inferior turbinates were treated between 1987 and 1994 with various carbon dioxide (CO2) and neodymium:yttrium-aluminum-garnet (Nd:YAG) laser techniques. We report on the therapeutic results of both types of laser turbinectomy and compare their long-term results with those of submucosal diathermy. Among the different techniques, we preferred the following approaches. The CO2 laser technique involved the application of a few laser spots (laser energy density 6,100 J/cm2 per lesion) to the head of the turbinate under the operating microscope. In the Nd: YAG laser procedure, diffuse, low-power irradiation (laser energy density < 53 kJ/cm2) of the entire concha was performed under endoscopic control. The CO2 laser procedure involved little bleeding and hardly any pain. It produced a positive effect after only a few days and required no follow-up treatment. The success of Nd: YAG laser treatment, by contrast, only became evident after weeks or months, due to the slow scarring process. Compared to submucosal diathermy, both laser methods produced better long-term results. Two years postoperatively, the overall success rate, as defined by patient satisfaction, was 79.6% for the CO2 laser, 68.3% for the Nd: YAG laser, and 36% for submucosal diathermy.

Fundamentals of radiation heat transfer in AlSi10Mg powder bed during selective laser melting

2019 ◽  
Vol 25 (9) ◽  
pp. 1506-1515 ◽  
Author(s):  
Pei Wei ◽  
Zhengying Wei ◽  
Zhne Chen ◽  
Jun Du ◽  
Yuyang He ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Energy Density ◽  
Negative Impact ◽  
Laser Energy ◽  
Melting Process ◽  
Laser Energy Density ◽  
Granular System ◽  
Laser Melting ◽  
Content Type ◽  
Powder Bed

Purpose This paper aims to study numerically the influence of the applied laser energy density and the porosity of the powder bed on the thermal behavior of the melt and the resultant instability of the liquid track. Design/methodology/approach A three-dimensional model was proposed to predict local powder melting process. The model accounts for heat transfer, melting, solidification and evaporation in granular system at particle scale. The proposed model has been proved to be a good approach for the simulation of the laser melting process. Findings The results shows that the applied laser energy density has a significantly influence on the shape of the molten pool and the local thermal properties. The relative low or high input laser energy density has the main negative impact on the stability of the scan track. Decreasing the porosity of the powder bed lowers the heat dissipation in the downward direction, resulting in a shallower melt pool, whereas pushing results in improvement in liquid track quality. Originality/value The randomly packed powder bed is calculated using discrete element method. The powder particle information including particle size distribution and packing density is taken into account in placement of individual particles. The effect of volumetric shrinkage and evaporation is considered in numerical model.

Effects of laser energy density on in situ formation of nano-graphite

2019 ◽  
Vol 48 (5) ◽  
pp. 506004
Author(s):  
刘孝谦 Liu Xiaoqian ◽  
骆 芳 Luo Fang ◽  
杜琳琳 Du Linlin ◽  
陆潇晓 Lu Xiaoxiao
Keyword(s):  
Energy Density ◽  
Laser Energy ◽  
Laser Energy Density ◽  
In Situ Formation
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