Papers by Keyword: Diode Laser

Abstract: Laser surface treatment is at present one of up-to-date methods for surface layer engineering, in this technique into the matrix material are introduced some amount of alloying additives. So the surface layer is obtained in form of composite material consisting of ceramic particle powders with different properties influencing the surface layer appliance possibilities. Using the technology it is possible to obtain a layer revealing a structured structure consisting of the heat affected zone (HAZ), transition zone (TZ) and remelted zone (RZ), as well as the substrate material. The laser is without cracks and defects as well as has with a slightly higher hardness value compared to the raw substrate material. The used laser power range is set in the range between 1.0 to 2.5 Kw, with the laser scan rate of the beam head in a range between 0.25-0.75 m/min, depending of the applied laser power and material used for alloying.This study was conducted to determine the effect of carbide on oxide ceramic powders addition on the microstructure and mechanical properties their changes and enhancement possibilities during a rapid solidification process of the remelted surface layer. The investigation should help to use this laser treatment technology for alloying of ceramic powder particles into the surface of light alloys, especially magnesium and aluminium. The scientific reason of this work is the usage of High Power Diode Laser (HPDL) for improvement of aluminium`s mechanical properties, especially the surface hardness and war resistance.There was found during the investigations and analysis of the results that, the obtained surface layer is without cracks and defects as well as with a relatively higher hardness compared to the raw material, after standard heat treatment. The hardness value increases according to the laser power used so that the highest power applied gives the highest hardness value in the remelted layer, similar relation can be found in the wear resistance parameters, which increases also with increasing laser power.The findings of the investigations allows to state, that the distribution of the used ceramic particles is generally satisfied, especially the carbide powder was confirmed in the alloys matrix, the particles are mainly present in the upper part of the surface layer or in the bottom zone of the remelted area. The hardness value increases in general according to the laser power used and the highest power results with the highest hardness value in the surface layer. The main aim of this work is to investigate and determine the effect of HPDL remelting and alloying on the cast Al-Si-Cu and Mg-Al-Cu cast aluminium and cast magnesium alloys micro structure for possible application in real working conditions mainly for light metal constructions as well as in many branches of the industry like automotive and rail transportation.

Abstract: Three mechanisms of titanium matrix composite Ti/TiN formation during diode laser nitriding of Ti6Al4V alloy in liquid stage were identified and discussed. When the titanium alloy surface is melted by a laser beam the first mechanism of nucleation and growth of d-TiN was identified in the temperature range of melt pool from 1650 up to 2320 °C, when the nitrogen concentration in the Tia solution reaches at least to the concentration limit in a range 20,5 to 22 at. %. Next different mechanism of nucleation of d-TiN was identified in the temperature range of melt pool from 2320 up to 2950 °C. In turn, the third mechanism of d-TiN formation was identified above the melting point of titanium nitrides, i.e. 2950 °C.

Abstract: Based on the wide range study of laser gas nitriding (LGN) of commercially pure titanium and the titanium alloy Ti6Al4V by means of high power direct diode laser (HPDDL), the kinetics of nitrogen absorption by the melt pool and related titanium nitrides growth was analyzed. Also a schematic model of nitrogen absorption by the melt pool was proposed. According to the hypothetical model three cases of nitrogen absorption by the melt pool were be distinguished and discussed. It was found that in a case of HPDDL nitriding of the Ti6Al4V alloy the presence of a thin homogenous layer of TiNx on the top surface of melt pool affects the nitrogen absorption kinetics. The process of nitrogen desorption at the cooling stage of melt pool is inhibited by the layer of TiNx as well as by the phase transformation and titanium nitrides formation.

Abstract: The effect of the output power with different facet passivation methods on 980 nm graded index waveguide structure InGaAs/AlGaAs laser diodes was studied. The output power of the 980 nm laser diodes with Si passivation, and ZnSe passivation at the front and the back facet were compared. The test results show that output power of the ZnSe passivation method is 11% higher than Si passivation method. The laser diode with the Si passivation film is failure when current is 5.1 A, the laser diode with the ZnSe passivation film is not failure until current is 5.6 A And we analyzed the failure reasons for each method. In conclusion, the method of coated ZnSe passivation on the laser diode facet can effectively increase the output power of semiconductor lasers.

Abstract: The influence of the nitrogen content in argon/nitrogen gas mixture on mechanism of titanium nitrides formation during laser surface processing of titanium alloy Ti6Al4V with high power diode laser was investigated. The phase composition and microhardness on cross-section of surface layers were analyzed and described. It was found that the nucleation of TiN dendrites in nitrogen rich atmosphere (at least 75 % of N₂) takes place on the liquid/gas boundary as a result of the reaction between molten titanium and gaseous nitrogen. The subsequent growth of titanium nitride dendrites (crystallization) proceeds into the liquid metal (weld pool), perpendicularly to the top surface. High length of the titanium nitride dendrites up to 180÷250 μm in the surface layer produced in pure nitrogen atmosphere indicates also very rapid rate of dendrites growth in the molten titanium. The tendency to form titanium nitrides during laser surface processing of the investigated titanium alloy falls dawn with the decrease of nitrogen content in the gas mixture.

Abstract: The heat conditions of laser gas nitriding (LGN) of titanium alloy Ti6Al4V by high power diode laser (HPDL) were investigated experimentally by non-contact pyrometric measurements and infrared camera analysis. Additionally direct observations of the weld pool shape were conducted by means of high speed digital camera. In the numerical study of the laser surface processing of titanium plate 3D model of heat flow was examined. Results of temperature values, distribution and temperature isotherms obtained from the 3D model were next applied in the two-dimensional stationary model of liquid metal flow in the weld pool. Experimental and numerical study showed that the temperatures of the weld pool during laser gas nitriding of the titanium alloy are significantly higher compared to these determined during laser melting in argon atmosphere at the same heat input. Additionally severe turbulences of liquid metal in the weld poll (Marangoni convection) were found during both experimental and numerical analysis.

Abstract: Direct diode lasers have some of the most attractive features of any laser. They are very efficient, compact, wavelength versatile, low cost, and highly reliable. However, the full utilization of direct diode lasers has yet to be realized. This is mainly due their poor output beam quality. Because of this, direct diode lasers are typically used to pump other lasers such as bulk solid-state (rod and thin disk) and fiber lasers. An improvement of the wall-plug efficiency and Power density necessary can be achieved by beam shaping and beam combination such as polarization coupling. In this paper, using the beam shaping technology realize good beam quality and high wall-plug efficiency. Base on bars rated to 60 W and 57% conversion efficiency, vertically stacked arrays (twenty bars) of such configuration are demonstrated with rated to about 1200W. The beam quality of high-power high brightness 880 nm laser diode source is improved with beam shaping. Beam parameter product of 79. 3 mm mrad ×81. 2 mm mrad, electro-optical conversion efficiency of more than 45.8% and continuous output power of 1 kW are demonstrated. This laser can be directly applied to cladding, surface hardening and other fields.

Abstract: The digital Semiconductor Laser’s Driving Source is designed in this paper, in order to gain a constant current source, which the maximize output electric current is 40A; voltage is from 2V to 10V. Based on the requirement of very task, the part of driving and the part of constant temperature control, which is auxiliary designed, are made of the controller of semiconductor laser diode. As the result, the whole of designs ensure the diode laser to work stably.

Abstract: As the increasing applications of laser diodes in laser cladding and laser hardening, the single laser diode 0ptical power can not meet the actual requirements. An improvement of the power and Power densty necessary and it can be achieved by beam shaping and beam combination such as polarization coupling the polarization coupling technology is used to couple two laser beams with thin film plate polarizer In this paper two 880 nm vertical stacked arrays with an output power of l600 W was achieved After fast axils and slow axis collimated, the polarization direction of one stacked arrays is rotated 90 degree through a half wave plate, thus, the polarization directions of two laser stack are vertica1. The beams of two lasers are incident on the p1ate po1arizer, one transmits through it, and the other is reflected on it. Finally, two beams combine to one. Polarization coupling of two bars increases the power by a factor of 1.6, and the output power is 2500 W, electro optical conversion efficiency is more than 48%. The spot size is about2 mm x 2 mm. This laser can be directly applied to cladding, surface hardening and other fields.

Abstract: Laser diode has incited particular interest as photoelectric conversion efficiency, output power and lifetime for a variety of applications in industry processing. The single laser diode optical power has not satisfied for the actual requirements. It demands to couple several diode laser beams into one beam to output directly or by an optical fiber to improve the brightness, and it becomes the central issue to adopt the appropriate beam coupling technology which would offer high quality and high efficiency. In order to output high power, we utilized wavelength coupling technology to couple two laser beam of different wavelength together with beam splitter cube (BSC), the key technology and the principle of wavelength coupling is indicated and analyzed in this paper .Using 808nm and 980nm laser diode realize wavelength coupling with high output power, the efficiency more than 80% and spot size can be achieved after focusing to the beam size of 3×3mm².