Effect Of Laser Beam Diameter Research Articles

Investigation of mortality rate of Drosophila melanogaster irradiated with nanosecond passively Q-switched microchip laser

Lasers have been widely used for pest control because they are efficient and effective to kill pests. Efficient pest control has been achieved with pulsed lasers, however, there is less investigation of effects of pulse characteristics on the pest mortality. Here, the effects of laser beam diameter, pulse width, peak power, and repetition rate of a compact passively Q-switched microchip laser on the mortality rate of Drosophila melanogaster have been studied. The lethality dosing for 90% mortality rate (LD90) Drosophila melanogaster has been utilized for evaluating the effects of passively Q-switched laser on mortality of insects. The beam diameter comparable to the size of Drosophila melanogaster is effective and economic for killing insects. The energy fluence required for LD90 decreases about 6.5% as pulse width is shortened from 1.5 ns to 850 ps. The energy fluence required for LD90 decreases about one-third as the peak power of passively Q-switched microchip laser increases four times from 6.94 kW to 27.48 kW. The energy fluence required for LD90 decreases dramatically from 16.02 J/cm2 to 12.77 J/cm2 as repetition rate increases from 5.05 kHz to 9.9 kHz and then tends to keep as a constant around 12.7 kHz with further increase of repetition rate. Nanosecond passively Q-switched microchip laser with high peak power and high repetition rate is a promising light source for effective and efficient pest control.

Effect of Laser Beam Diameter on the Microstructure and Hardness of 17-4 PH Stainless Steel Additively Manufactured by Direct Energy Deposition

Effect of Laser Beam Diameter on the Microstructure and Hardness of 17-4 PH Stainless Steel Additively Manufactured by Direct Energy Deposition

Analysis of Roughness and Heat Affected Zone of Steel Plates Obtained by Laser Cutting

In the present study, high-power CO2 laser cutting of steel plates has been investigated and the effect of the input laser cutting parameters on the cut surface quality is analyzed. The average roughness of the cut surface of the specimens, produced by different laser beam diameter and laser power, were measured by using roughness tester. The scanning electron microscopy SEM is used to record possible metallurgical alterations on the cut edge. The aim of this work is to investigate the effect of laser beam diameter and laser power on the cut surface roughness and on the heat affected zone width HAZ of steel plates obtained by CO2 laser cutting. An overall optimization was applied to find out the optimal cutting setting that would improve the cut surface quality. It was found that laser beam diameter has a negligible effect on surface roughness but laser power had major effect on roughness. The cut surface roughness decreases as laser power increases. Improved surface roughness can be obtained at higher laser power. Also, laser beam diameter and laser power had major effect on HAZ width. It increases as laser power increases.

Effect of Laser Beam Diameter on Cut Edge of Steel Plates Obtained by Laser Machining

Laser cutting is a thermal process which is used contactless to separate materials. In the present study, high-power laser cutting of steel plates is considered and the thermal influence of laser cutting on the cut edges is examined. The microstructure and the microhardness of the cut edge are affected by the input laser cutting parameter: laser beam diameter. The aim of this work is to investigate the effect of the laser beam diameter on the microhardness beneath the cut surface of steel plates obtained by CO2 laser cutting. The cut surface was studied based on microhardness depth profiles beneath the machined surface. The results show that laser cutting has a thermal effect on the surface microstructure and on the microhardness beneath the cut section. Also the microhardness of the hardening zone depends on the laser beam diameter.

Effects of laser beam diameter on electromagnetically induced transparency due to Zeeman coherences in Rb vapor

We experimentally studied the effects of laser beam diameter on electromagnetically induced transparency (EIT) due to Zeeman coherences induced by a laser resonant with the hyperfine transition Fg = 2 → Fe = 1 of 87Rb in a rubidium buffer gas cell. We use two laser beams of Gaussian intensity radial profile for laser beam diameters of 6.5 and 1.3 mm, laser intensities in the range of 0.1–35 mW cm−2 and cell temperatures between 60 and 82 °C. The results show that the amplitude of the normalized EIT resonance has a maximum at a laser intensity which depends on laser beam diameter and cell temperature. The laser intensity corresponding to the maximum EIT amplitude is higher for a smaller laser beam and higher cell temperature. The linewidth of Zeeman EIT resonance varies nearly linearly with laser intensity, almost independent of cell temperature and laser beam diameter.

CO2and Er:YAG laser interaction with grass tissues

Plant leaves are multi-component optical materials consisting of water, pigments, and dry matter, among which water is the predominant constituent. In this article, we investigate laser interaction with grass using CO2 and Er:YAG lasers theoretically and experimentally, especially targeting water in grass tissues. We have first studied the optical properties of light absorbing constituents of grass theoretically, and then have identified interaction regimes and constructed interaction maps through a systematic experiment. Using the interaction maps, we have studied how interaction regimes change as process parameters are varied. This study reveals some interesting findings concerning carbonization and ablation mechanisms, the effect of laser beam diameter, and the ablation efficiency and quality of CO2 and Er:YAG lasers.

Effect of Laser Beam Diameter Variation in Saturated Absorption Spectra

In this study, we examined the effect of pump laser beam diameter on saturated absorption spectra. The rate equations describing the dynamics of the population of each sublevel were solved and the time evolution of the signals was obtained theoretically. With the exception of some signals, the experimental results showed good agreement with the calculated results, which were analyzed using the calculation based on rate equations. Furthermore, the beam diameter dependence of the spectra was examined for several pump beam intensities, and the results matched the calculated results.

High speed welding of aluminium alloy sheets using laser assisted alternating current pulsed metal inert gas process

Abstract Alternating current pulsed metal inert gas welding is an appropriate process for joining aluminium alloy sheets because of its great gap tolerance and low heat input, which assists in avoiding burn through. However, when welding speed is higher than 2 m min-1 the low heat input is no longer an advantage since lack of penetration becomes a problem. Irradiation of the vicinity of the arc using a laser beam can solve this problem, and adjustment of the laser power can control the penetration. As a result, thin aluminium alloy sheets can be joined at a high speed of 4 m min-1 with sufficient gap tolerance. Moreover, investigation of the effect of laser beam diameter on the resulting weld for thin sheets indicates that a defocused laser beam having a diameter of several millimetres can further improve the ability to bridge joint gaps and tolerance of deviations in torch aim. Consequently, a high power diode laser having a relatively thick beam waist is suitable for this application.

MECHANICAL ALIGNMENT USING LASER DIODES AND SINGLE ELEMENT PHOTO-DETECTORS; RESOLUTION ENHANCEMENT

This paper studies the use of laser diodes and single element photo-detectors in mechanical alignment. Considering Gaussian beam theoretical model, the effect of laser beam diameter is studied using computer simulation. Optimum conditions that give the highest sensitivity are proved to be where:(i) the laser beam diameter matches the diameter of the sensitive area of the detector.(ii) the laser beam waist is located at the sensitive area of the detector.The photo-detector with two-complement sensitive area has been studied as a better replacement of a single area photodetector. It was proved that the use of this type of detectors , with all of the other parameters unchanged, doubles the alignment sensitivity. Finally, an experimental verification has been performed which gives a good agreement with the results obtained by computer simulation, where an alignment sensitivity of ± 0.3558 ttm was obtained.

Spray characteristics of twin-fluid atomization using external-mixing sonic nozzles

Spray characteristics of external mixing sonic twin-fluid atomization nozzles are investigated experimentally. Particle sizes are measured by the Fraunhofer diffraction method using the Malvern particle analyzer, and their radial distributions are obtained using the tomographical transformation technique. The spatial distribution of SMD shows that the drop size increases in the radial direction at a fixed liquid flow rate, and the distribution is getting uniform rapidly as the atomizing gas pressure increases. The SMD decreases as the liquid flow rate increases at a fixed GLR. It is found that the atomization efficiency of the flush type sonic nozzle is superior to that of protrusion type. The effect of laser beam diameter of the particle analyzer on the spatial SMD distribution is minor at present experimental conditions.