Dear Editor,In this case,we discuss a teenager who experienced severe eye pain and elevated intraocular pressure(IOP)caused by reverse pupillary block,which was successfully resolved using Neodymium-doped yttrium alum...Dear Editor,In this case,we discuss a teenager who experienced severe eye pain and elevated intraocular pressure(IOP)caused by reverse pupillary block,which was successfully resolved using Neodymium-doped yttrium aluminum garnet(Nd:YAG)laser peripheral iridotomy(LPI).展开更多
In this paper,we present a high peak power passively Q-switched intracavity frequency-doubled green laser based on an efficient LED-pumped Nd:YAG dual-rod laser module.In quasi-continuous wave(QCW)running operation,th...In this paper,we present a high peak power passively Q-switched intracavity frequency-doubled green laser based on an efficient LED-pumped Nd:YAG dual-rod laser module.In quasi-continuous wave(QCW)running operation,the average output power of the fundamental laser at 1064 nm reaches as high as 20.98 W at a repetition rate of 50 Hz with a maximum single pulse energy of 419.6 mJ,corresponding to a maximum optical conversion efficiency of 38.8%and a slope efficiency of 41%.展开更多
AIM: To study the efficacy and the safety of laser lithotripsy without direct visual control by using a balloon catheter in patients with bile duct stones that could not be extracted by standard technique. METHODS: Th...AIM: To study the efficacy and the safety of laser lithotripsy without direct visual control by using a balloon catheter in patients with bile duct stones that could not be extracted by standard technique. METHODS: The seventeen patients (7 male and 10 female; mean age 67.8 years) with difficult common bile duct (CBD) stones were not amenable for conventional endoscopic maneuvers such as sphincterotomy and mechanical lithotripsy were included in this study. Laser wavelengths of 532 nm and 1064 nm as a double pulse were applied with pulse energy of 120 mJ. The laser fiber was advanced under fluoroscopic control through the ERCP balloon catheter. Laser lithotripsy was continued until the fragment size seemed to be less than 10 mm. Endoscopic extraction of the stones and fragments was performed with the use of the Dormia basket and balloon catheter. RESULTS: Bile duct clearance was achieved in 15 of 17 patients (88%). The mean number of treatment sessions was 1.7 ± 0.6. Endoscopic stone removal could not be achieved in 2 patients (7%). Adverse effects were noted in three patients (hemobilia, pancreatitis, and cholangitis). CONCLUSION: The Frequency Doubled Double Pulse Nd:YAG (FREDDY) laser may be an effective and safe technique in treatment of difficult bile duct stones.展开更多
The experiment of Nd： YAG pulsed laser self-fluxing welding for 304 stainless steel/Ti6Al4V titanium alloy dissimilar metal was carried out. The microstructure properties of welded joint were analyzed by SEM, EDS and...The experiment of Nd： YAG pulsed laser self-fluxing welding for 304 stainless steel/Ti6Al4V titanium alloy dissimilar metal was carried out. The microstructure properties of welded joint were analyzed by SEM, EDS and XRD. The equilibrium lattice constants, enthalpies of formation, cohesive energies, mechanical properties, Debye temperatures and valence electron structures of Ti-Fe intermetallic compounds （IMCs） were calculated by the first principle pseudopotential plane wave method based on density functional theory （DFT）. According to the thermodynamic data of Ti-Fe-Cr compounds, the Gibbs free energy per mole of compound at different temperatures was calculated and their thermal stability was compared. The results show that there are no macroscopic cracks in the welded joints, and the IMCs distributed evenly along the welding interface exhibits 3 distinct layers of microstructure with different colors. The welds interface generates IMCs of TiFe, TiFe 2 and a small amount of Ti 5Cr 7Fe 17 IMCs. Ti-Fe IMCs with high thermodynamic stability and easy alloying formation. The results of Gibbs free energies show that the sequence of precipitates in the interface is Ti 5Cr 7Fe 17 , TiFe 2 and TiFe in high temperature during the metallurgical reaction. The G/B values of Ti-Fe IMCs are greater than the critical value of 0.5, indicating that it is an intrinsic brittleness.展开更多
We successfully obtain a high-average-power high-stability Q-switched green laser based on diode-side-pumped composite ceramic Nd：YAG in a straight piano-concave cavity. The temperature distribution in composite cera...We successfully obtain a high-average-power high-stability Q-switched green laser based on diode-side-pumped composite ceramic Nd：YAG in a straight piano-concave cavity. The temperature distribution in composite ceramic Nd：YAG crystal is numerically analyzed and compared with that of conventional Nd：YAG crystal. By using a composite ceramic Nd：YAG rod and a type-II high gray track resistance KTP （HGTR-KTP） crystal, a green laser with an average output power of 165 W is obtained at a repetition rate of 25 kHz, with a diode-to-green optical conversion of 14.68%, and a pulse width of 162 ns. To the best of our knowledge, both the output power and optical-to-optical efficiency are the highest values for green laser systems with intracavity frequency doubling of this novel composite ceramic Nd：YAG laser to date. The power fluctuation at around 160 W is lower than 0.3% in 2.5 hours.展开更多
AIM: To evaluate the outcome of laser iridotomy using532-nm Nd: YAG laser(PASCAL) with short pulse duration and Nd: YAG laser compared to conventional combined laser iridotomy.METHODS: Retrospective, nonrandomized, co...AIM: To evaluate the outcome of laser iridotomy using532-nm Nd: YAG laser(PASCAL) with short pulse duration and Nd: YAG laser compared to conventional combined laser iridotomy.METHODS: Retrospective, nonrandomized, comparative case series. Forty-five eyes of 34 patients underwent laser iridotomy. Twenty-two eyes underwent iridotomy using short duration PASCAL and Nd: YAG laser, and 23 eyes underwent iridotomy using conventional combined laser method. The average settings of PASCAL were60 μm and 700-900 m W with a short duration of 0.01 s to reduce the total applied energy. The conventional laser was 50 μm and 700-900 m W for 0.1s. After photocoagulation with these laser, the Nd: YAG laser was added in each group. Endothelial cell counts of preiridotomy and 2mo after iridotomy were measured and compared.RESULTS: All eyes completed iridotomy successfully.The total energy used in the PASCAL group was 1.85 ±1.17 J. Compared to conventional laser 13.25 ±1.67 J, the energy used was very small due to the short exposure time of PASCAL. Endothelial cell counts were reduced by0.88% in the PASCAL group and 6.72% in the conventional laser group(P =0.044). The change in corneal endothelial cell counts before and after iridotomy was significant in conventional combined laser iridotomy group(P =0.004).CONCLUSION: Combined PASCAL and Nd:YAG laseriridotomy is an effective and safe technique in the dark brown irides of Asians. Furthermore, the short duration of exposure in PASCAL offers the advantages of reducing the total energy used and minimizing the corneal damage.展开更多
A pulsed Nd：YAG （yttrium aluminum garnet） laser-based technique was employed to clad low silicon steel with preplaced Si and Fe mixed powders for high Si content. The surface morphology, microstructural evolution, ...A pulsed Nd：YAG （yttrium aluminum garnet） laser-based technique was employed to clad low silicon steel with preplaced Si and Fe mixed powders for high Si content. The surface morphology, microstructural evolution, phase composition, and Si distribution, within the obtained cladding coatings, were characterized by optical microscopy （OM）, field emission scanning electron microscopy （FE-SEM）, with associated energy dispersive spectroscopy （EDS）, transmission electron microscopy （TEM）, and X-ray diffraction （XRD）. The microhardness was also measured along the depth direction of the specimens, A crack- and pore-free cladding coating through excellent metallurgical bonding with the substrate was successfully prepared on low silicon steel by means of optimized single-track and multi-track laser cladding. The phases of the coating are a-Fe, T-Fe, and FeSi. The high microhardness of the lasercladding zone is considered as an increase in Si content and as the refined microstructure produced by the laser treatment. The Si contents of the cladding coatings were about 5.8wt% in the single-track cladding and 6.5wt% in the multi-track cladding, respectively.展开更多
The objective of the this study is to investigate the effects of cutting parameters on thermal characteristics, including practical cutting regions, the formation of the kerfwidth and the heat transfer phenomenon, in ...The objective of the this study is to investigate the effects of cutting parameters on thermal characteristics, including practical cutting regions, the formation of the kerfwidth and the heat transfer phenomenon, in the cutting of Inconel 718 super-alloy sheets using a CW Nd：YAG laser. From the results of the experiments, the influence of process parameters on both the practical cutting region and the kerfwidth has been examined. In addition, it has been shown that the kerfwidth of the specimen lies in the range of 0.53-0.61 mm. In order to examine characteristics of the heat transfer during the laser cutting process, a three-dimensional quasi-steady heat transfer analysis has been performed using the commercial code SYSWELD V9.0. From the results of the analysis, the influence of cutting parameters on the temperature distribution in the vicinity of the cut section has been quantitatively evaluated. Based on these results, optimal cutting conditions have been estimated.展开更多
A diode-end-pumped Q-switched high-efficiency Nd, Cr：YAG laser with simultaneous dual-wavelength emission at 946nm and 1.3μm is demonstrated. The maximum output power of 1.93 W with simultaneous dual-wavelength oper...A diode-end-pumped Q-switched high-efficiency Nd, Cr：YAG laser with simultaneous dual-wavelength emission at 946nm and 1.3μm is demonstrated. The maximum output power of 1.93 W with simultaneous dual-wavelength operation is achieved at an absorbed pump power of 13.32 W and an absorbed slope efficiency of 15.15%. The maximum optical-optical efficiency is 14.49% with pulse widths of 16.38ns at 946nm and 26.65ns at 1.3μm. A maximum total repetition rate of 43.25 kHz is obtained.展开更多
This paper demonstrated a high power and high beam quality diode-pumped 1319-nm Nd：YAG master oscillator-power amplifier laser system. A thermally near-unstable resonator with four-rod birefringence compensation fiat...This paper demonstrated a high power and high beam quality diode-pumped 1319-nm Nd：YAG master oscillator-power amplifier laser system. A thermally near-unstable resonator with four-rod birefringence compensation fiat-fiat cavity was adopted as the master oscillator. A solid etalon was inserted in the unidirectional ring resonator to compress the laser linewidth. Under a repetition rate of 500 Hz and pulse width of 160 μs, the master oscillator delivers an average output power of 16.8 W at 1319 nm with linear polarisation, beam quality factor M^2=1.16 and linewidth of 3.2 GHz. A double-pass power amplifier with two amplifier stages was employed for higher power scaling and the output power was amplified to be 25.9 W with M^2 = 1.43.展开更多
Spectroscopic properties of flashlamp pumped Nd^3＋：YAG laser are studied as a function of temperature in a range from-30℃ to 60℃. The spectral width and shift of quasi three-level 946.0-nm inter-Stark emission wit...Spectroscopic properties of flashlamp pumped Nd^3＋：YAG laser are studied as a function of temperature in a range from-30℃ to 60℃. The spectral width and shift of quasi three-level 946.0-nm inter-Stark emission within the respective intermanifold transitions of ^4F3/2→^4I9/2are investigated. The 946.0-nm line shifts toward the shorter wavelength and broadens. In addition, the threshold power and slope efficiency of the 946.0-nm laser line are quantified with temperature.The lower the temperature, the lower the threshold power is and the higher the slope efficiency of the 946.0-nm laser line is,thus the higher the laser output is. This phenomenon is attributed to the ion-phonon interaction and the thermal population in the ground state.展开更多
We first experimentally demonstrate a laser-diode end-pumped self-Q-switched and mode-locked Nd,Cr：YAG green laser with a KTP crystal as the intra-cavity frequency doubler. The device produces an average output power...We first experimentally demonstrate a laser-diode end-pumped self-Q-switched and mode-locked Nd,Cr：YAG green laser with a KTP crystal as the intra-cavity frequency doubler. The device produces an average output power of 680 mW at 532 nm. The corresponding pulse width of the Q-switched envelope of the green laser is 170 ＋ 20 ns. The mode-locked pulses have a repetition rate of approximately 183 MHz and the average pulse duration is estimated to be around sub-nanosecond. It is found that the intra-cavity frequency doubling greatly improves the modulation depth and stability of the mode-locked pulses within the Q-switched envelope.展开更多
By using a Nd: YAG laser welding system devised for transmitting continuous, rectangular and pulsed waveforms, comprehensive and deep investigation is focused on the effects of several parameters of rectangular wavefo...By using a Nd: YAG laser welding system devised for transmitting continuous, rectangular and pulsed waveforms, comprehensive and deep investigation is focused on the effects of several parameters of rectangular waveform and pulsed output wave superimposed on a rectangular waveform on the penetration depth of weld. Research results indicate that the average power, duty cycle, frequency and peak power of rectangular wave affect the weld penetration depth to different extent. Results of experiments and analysis also indicate that the pulse delay time, pulse width and the power ratio of pulse to rectangular waveform seriously influence the penetration when the pulsed wave is superimposed on a rectangular waveform.展开更多
The effects of picosecond Nd:YAG laser irradiation on chemical and morphological surface characteristics of the commercially pure titanium and Ti–13Nb–13Zr alloy in air and argon atmospheres were studied under diffe...The effects of picosecond Nd:YAG laser irradiation on chemical and morphological surface characteristics of the commercially pure titanium and Ti–13Nb–13Zr alloy in air and argon atmospheres were studied under different laser output energy values.During the interaction of laser irradiation with the investigated materials,a part of the energy was absorbed on the target surface,influencing surface modifications.Laser beam interaction with the target surface resulted in various morphological alterations,resulting in crater formation and the presence of microcracks and hydrodynamic structures.Moreover,different chemical changes were induced on the target materials’surfaces,resulting in the titanium oxide formation in the irradiation-affected area and consequently increasing the irradiation energy absorption.Given the high energy absorption at the site of interaction,the dimensions of the surface damaged area increased.Consequently,surface roughness increased.The appearance of surface oxides also led to the increased material hardness in the surface-modified area.Observed chemical and morphological changes were pronounced after laser irradiation of the Ti–13Nb–13Zr alloy surface.展开更多
A high-power passively Q-switched Nd：YAG laser operating at lll2nm with Cr4＋：yAO as a saturable absorber is demonstrated. Under 808 nm diode-direct pumping, the maximum average output power of 2.73 W is achieved at...A high-power passively Q-switched Nd：YAG laser operating at lll2nm with Cr4＋：yAO as a saturable absorber is demonstrated. Under 808 nm diode-direct pumping, the maximum average output power of 2.73 W is achieved at the pump power of 16.65 W, corresponding to an optical-to-optical conversion efficiency of 16.4%. At the same time, the pulse width, pulse repetition rate, single pulse energy and peak power are 27.2ns, 9 kHz, 303.3#3 and 11.2kW, respectively. As far as we know, the result gives the highest average output power at 1112nm generated by an 808 nm diode-end-pumped Nd：YAG laser.展开更多
This study deals with Nd：YAG laser cutting nonmetallic materials, which is one of the most important and popular industrial applications of laser. The main theme is to evaluate the effects of Nd：YAG laser beam power...This study deals with Nd：YAG laser cutting nonmetallic materials, which is one of the most important and popular industrial applications of laser. The main theme is to evaluate the effects of Nd：YAG laser beam power besides work piece scanning speed. For approximate cutting depth, a theoretical study is conducted in terms of material property and cutting speed. Results show a nonlinear relation between the cutting depth and input energy. There is no significant effect of speed on cutting depth with the speed being larger than 30 mm/s. An extra energy is utilized in the deep cutting. It is inferred that as the laser power increases, cutting depth increases. The experimental outcomes are in good agreement with theoretical results. This analysis will provide a guideline for laser-based industry to select a suitable laser for cutting, scribing, trimming, engraving, and marking nonmetallic materials.展开更多
Performance of an LD-end-pumped passively Q-switched Nd： YA G/Cr4＋ ： YA G microchip laser operating at 1123 nm is studied. A maximum average output power of 517row with an optical-to-optical conversion efficiency o...Performance of an LD-end-pumped passively Q-switched Nd： YA G/Cr4＋ ： YA G microchip laser operating at 1123 nm is studied. A maximum average output power of 517row with an optical-to-optical conversion efficiency of 12.6% and a slope efficiency of 25.8% is obtained under a pump power of 4.1 W. A minimum pulse width of 1.1 ns with a pulse repetition rate of 20.2kHz is obtained, and the corresponding pulse energy and peak power are 25.6μJ and 23.3kW, respectively. To our knowledge, the 23.3kW peak power is the highest among 1123nm lasers. Additionally, based on the 1123 nm laser, with LBO as the frequency doubler, a 288-mW green-yellow laser at 561 nm is successfully achieved.展开更多
Exploiting a specially designed Fabry-Perot filter as output coupler,a continuous 1052 nm and 1061 nm dual-wavelength laser is realized.The threshold,slope efficiency and maximum power of the 1052 nm and 1061 nm dual-...Exploiting a specially designed Fabry-Perot filter as output coupler,a continuous 1052 nm and 1061 nm dual-wavelength laser is realized.The threshold,slope efficiency and maximum power of the 1052 nm and 1061 nm dual-wavelength laser are 2.55 W,17.5%and 571 mW,respectively.The competition and coexistent relationships between 1052 nm,1061 nm and 1064 nm are analyzed.Involved non-degenerate Stark energy level structures are used to classify dual-wavelength lasers.According to this method,dual-wavelength lasers can be classified as different upper and lower non-degenerate Stark energy levels,the same upper but different lower Stark energy levels,different upper but the same lower Stark energy levels.Representative Nd:YAG dual-wavelength lasers are classified according to this criterion.It is found that the realization of front two type lasers is easy and that of third type lasers is challenging.This method can be used as a level of difficulty reference for the realization of dual-wavelength lasers.展开更多
The main aim of this research is to optimize the tensile strength of laser welded FeCo-V alloy.A mathematicalrelationship was developed to predict tensile strength of the laser beam welded FeCo-V foils by incorporatin...The main aim of this research is to optimize the tensile strength of laser welded FeCo-V alloy.A mathematicalrelationship was developed to predict tensile strength of the laser beam welded FeCo-V foils by incorporating process parameterssuch as lamping current,welding speed,pulse duration and focused position.The procedure was established to improve the weldstrength and increase the productivity.The results indicate that the pulse duration and welding speed have the greatest influence ontensile strength.The obtained results showed that the tensile strength of the weld joints increase as a function of increasing pulseduration reaching to a maximum at a pulse duration value of2.25ms.Moreover,the tensile strength of joints increases with decreasein welding speed reaching to a maximum at a welding speed of125mm/min.It has been shown that increase in pulse duration anddecrease in welding speed result in increased effective peak power density and hence formation of more resistant welds.At higherpulse durations and lower welding speeds,the tensile strength of weld joints decreases because of formation of solidificationmicrocracks in the fusion zone.展开更多
文摘Dear Editor,In this case,we discuss a teenager who experienced severe eye pain and elevated intraocular pressure(IOP)caused by reverse pupillary block,which was successfully resolved using Neodymium-doped yttrium aluminum garnet(Nd:YAG)laser peripheral iridotomy(LPI).
基金supported by the Nanjing University of Posts and Telecommunications Foundation,China(Grant Nos.JUH219002 and JUH219007)the Key R&D Program of Shandong Province,China(Grant No.2021CXGC010202)。
文摘In this paper,we present a high peak power passively Q-switched intracavity frequency-doubled green laser based on an efficient LED-pumped Nd:YAG dual-rod laser module.In quasi-continuous wave(QCW)running operation,the average output power of the fundamental laser at 1064 nm reaches as high as 20.98 W at a repetition rate of 50 Hz with a maximum single pulse energy of 419.6 mJ,corresponding to a maximum optical conversion efficiency of 38.8%and a slope efficiency of 41%.
基金The 2007 research fund of Wonkwang University and Wonkwang Clinical Research Institute
文摘AIM: To study the efficacy and the safety of laser lithotripsy without direct visual control by using a balloon catheter in patients with bile duct stones that could not be extracted by standard technique. METHODS: The seventeen patients (7 male and 10 female; mean age 67.8 years) with difficult common bile duct (CBD) stones were not amenable for conventional endoscopic maneuvers such as sphincterotomy and mechanical lithotripsy were included in this study. Laser wavelengths of 532 nm and 1064 nm as a double pulse were applied with pulse energy of 120 mJ. The laser fiber was advanced under fluoroscopic control through the ERCP balloon catheter. Laser lithotripsy was continued until the fragment size seemed to be less than 10 mm. Endoscopic extraction of the stones and fragments was performed with the use of the Dormia basket and balloon catheter. RESULTS: Bile duct clearance was achieved in 15 of 17 patients (88%). The mean number of treatment sessions was 1.7 ± 0.6. Endoscopic stone removal could not be achieved in 2 patients (7%). Adverse effects were noted in three patients (hemobilia, pancreatitis, and cholangitis). CONCLUSION: The Frequency Doubled Double Pulse Nd:YAG (FREDDY) laser may be an effective and safe technique in treatment of difficult bile duct stones.
基金supported by the National High Technology Research and Development Program of China(Grant No.2013AA041003)the National Natural Science Foundation of China(Grant No.51365039)
文摘The experiment of Nd： YAG pulsed laser self-fluxing welding for 304 stainless steel/Ti6Al4V titanium alloy dissimilar metal was carried out. The microstructure properties of welded joint were analyzed by SEM, EDS and XRD. The equilibrium lattice constants, enthalpies of formation, cohesive energies, mechanical properties, Debye temperatures and valence electron structures of Ti-Fe intermetallic compounds （IMCs） were calculated by the first principle pseudopotential plane wave method based on density functional theory （DFT）. According to the thermodynamic data of Ti-Fe-Cr compounds, the Gibbs free energy per mole of compound at different temperatures was calculated and their thermal stability was compared. The results show that there are no macroscopic cracks in the welded joints, and the IMCs distributed evenly along the welding interface exhibits 3 distinct layers of microstructure with different colors. The welds interface generates IMCs of TiFe, TiFe 2 and a small amount of Ti 5Cr 7Fe 17 IMCs. Ti-Fe IMCs with high thermodynamic stability and easy alloying formation. The results of Gibbs free energies show that the sequence of precipitates in the interface is Ti 5Cr 7Fe 17 , TiFe 2 and TiFe in high temperature during the metallurgical reaction. The G/B values of Ti-Fe IMCs are greater than the critical value of 0.5, indicating that it is an intrinsic brittleness.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 61107086, 61172010, and 61101058)the Science and Technology Committee of Tianjin, China (Grant No. 11JCYBJC01100)the National High Technology Research and Development Program of China (Grant No. 2011AA010205)
文摘We successfully obtain a high-average-power high-stability Q-switched green laser based on diode-side-pumped composite ceramic Nd：YAG in a straight piano-concave cavity. The temperature distribution in composite ceramic Nd：YAG crystal is numerically analyzed and compared with that of conventional Nd：YAG crystal. By using a composite ceramic Nd：YAG rod and a type-II high gray track resistance KTP （HGTR-KTP） crystal, a green laser with an average output power of 165 W is obtained at a repetition rate of 25 kHz, with a diode-to-green optical conversion of 14.68%, and a pulse width of 162 ns. To the best of our knowledge, both the output power and optical-to-optical efficiency are the highest values for green laser systems with intracavity frequency doubling of this novel composite ceramic Nd：YAG laser to date. The power fluctuation at around 160 W is lower than 0.3% in 2.5 hours.
文摘AIM: To evaluate the outcome of laser iridotomy using532-nm Nd: YAG laser(PASCAL) with short pulse duration and Nd: YAG laser compared to conventional combined laser iridotomy.METHODS: Retrospective, nonrandomized, comparative case series. Forty-five eyes of 34 patients underwent laser iridotomy. Twenty-two eyes underwent iridotomy using short duration PASCAL and Nd: YAG laser, and 23 eyes underwent iridotomy using conventional combined laser method. The average settings of PASCAL were60 μm and 700-900 m W with a short duration of 0.01 s to reduce the total applied energy. The conventional laser was 50 μm and 700-900 m W for 0.1s. After photocoagulation with these laser, the Nd: YAG laser was added in each group. Endothelial cell counts of preiridotomy and 2mo after iridotomy were measured and compared.RESULTS: All eyes completed iridotomy successfully.The total energy used in the PASCAL group was 1.85 ±1.17 J. Compared to conventional laser 13.25 ±1.67 J, the energy used was very small due to the short exposure time of PASCAL. Endothelial cell counts were reduced by0.88% in the PASCAL group and 6.72% in the conventional laser group(P =0.044). The change in corneal endothelial cell counts before and after iridotomy was significant in conventional combined laser iridotomy group(P =0.004).CONCLUSION: Combined PASCAL and Nd:YAG laseriridotomy is an effective and safe technique in the dark brown irides of Asians. Furthermore, the short duration of exposure in PASCAL offers the advantages of reducing the total energy used and minimizing the corneal damage.
基金the National Natural Science Foundation of China (No.50474084).
文摘A pulsed Nd：YAG （yttrium aluminum garnet） laser-based technique was employed to clad low silicon steel with preplaced Si and Fe mixed powders for high Si content. The surface morphology, microstructural evolution, phase composition, and Si distribution, within the obtained cladding coatings, were characterized by optical microscopy （OM）, field emission scanning electron microscopy （FE-SEM）, with associated energy dispersive spectroscopy （EDS）, transmission electron microscopy （TEM）, and X-ray diffraction （XRD）. The microhardness was also measured along the depth direction of the specimens, A crack- and pore-free cladding coating through excellent metallurgical bonding with the substrate was successfully prepared on low silicon steel by means of optimized single-track and multi-track laser cladding. The phases of the coating are a-Fe, T-Fe, and FeSi. The high microhardness of the lasercladding zone is considered as an increase in Si content and as the refined microstructure produced by the laser treatment. The Si contents of the cladding coatings were about 5.8wt% in the single-track cladding and 6.5wt% in the multi-track cladding, respectively.
基金supported by a grant-in-aid for Regional Innovation Center (RIC), New Technology Development and Research Center of Laser Application in Chosun University, from ITEP and MOICEpartly supported by the National Core Research Center Program from MOST and KOSEF (No.R15-2006-022-01001-0)
文摘The objective of the this study is to investigate the effects of cutting parameters on thermal characteristics, including practical cutting regions, the formation of the kerfwidth and the heat transfer phenomenon, in the cutting of Inconel 718 super-alloy sheets using a CW Nd：YAG laser. From the results of the experiments, the influence of process parameters on both the practical cutting region and the kerfwidth has been examined. In addition, it has been shown that the kerfwidth of the specimen lies in the range of 0.53-0.61 mm. In order to examine characteristics of the heat transfer during the laser cutting process, a three-dimensional quasi-steady heat transfer analysis has been performed using the commercial code SYSWELD V9.0. From the results of the analysis, the influence of cutting parameters on the temperature distribution in the vicinity of the cut section has been quantitatively evaluated. Based on these results, optimal cutting conditions have been estimated.
基金Supported by the National Basic Research Program of China under Grant No 2013CB632704
文摘A diode-end-pumped Q-switched high-efficiency Nd, Cr：YAG laser with simultaneous dual-wavelength emission at 946nm and 1.3μm is demonstrated. The maximum output power of 1.93 W with simultaneous dual-wavelength operation is achieved at an absorbed pump power of 13.32 W and an absorbed slope efficiency of 15.15%. The maximum optical-optical efficiency is 14.49% with pulse widths of 16.38ns at 946nm and 26.65ns at 1.3μm. A maximum total repetition rate of 43.25 kHz is obtained.
基金Project supported by the National High Technology Research and Development Program and the National Natural Science Foundation of China (Grant No. 60508013)
文摘This paper demonstrated a high power and high beam quality diode-pumped 1319-nm Nd：YAG master oscillator-power amplifier laser system. A thermally near-unstable resonator with four-rod birefringence compensation fiat-fiat cavity was adopted as the master oscillator. A solid etalon was inserted in the unidirectional ring resonator to compress the laser linewidth. Under a repetition rate of 500 Hz and pulse width of 160 μs, the master oscillator delivers an average output power of 16.8 W at 1319 nm with linear polarisation, beam quality factor M^2=1.16 and linewidth of 3.2 GHz. A double-pass power amplifier with two amplifier stages was employed for higher power scaling and the output power was amplified to be 25.9 W with M^2 = 1.43.
基金Project supported by Estahban Branch,Islamic Azad University
文摘Spectroscopic properties of flashlamp pumped Nd^3＋：YAG laser are studied as a function of temperature in a range from-30℃ to 60℃. The spectral width and shift of quasi three-level 946.0-nm inter-Stark emission within the respective intermanifold transitions of ^4F3/2→^4I9/2are investigated. The 946.0-nm line shifts toward the shorter wavelength and broadens. In addition, the threshold power and slope efficiency of the 946.0-nm laser line are quantified with temperature.The lower the temperature, the lower the threshold power is and the higher the slope efficiency of the 946.0-nm laser line is,thus the higher the laser output is. This phenomenon is attributed to the ion-phonon interaction and the thermal population in the ground state.
基金Project supported by the National Natural Science Foundation of China （Grant Nos 60278024 and 60438020）.
文摘We first experimentally demonstrate a laser-diode end-pumped self-Q-switched and mode-locked Nd,Cr：YAG green laser with a KTP crystal as the intra-cavity frequency doubler. The device produces an average output power of 680 mW at 532 nm. The corresponding pulse width of the Q-switched envelope of the green laser is 170 ＋ 20 ns. The mode-locked pulses have a repetition rate of approximately 183 MHz and the average pulse duration is estimated to be around sub-nanosecond. It is found that the intra-cavity frequency doubling greatly improves the modulation depth and stability of the mode-locked pulses within the Q-switched envelope.
基金Sponsored by National Science Fund!( 59881 0 0 2 )
文摘By using a Nd: YAG laser welding system devised for transmitting continuous, rectangular and pulsed waveforms, comprehensive and deep investigation is focused on the effects of several parameters of rectangular waveform and pulsed output wave superimposed on a rectangular waveform on the penetration depth of weld. Research results indicate that the average power, duty cycle, frequency and peak power of rectangular wave affect the weld penetration depth to different extent. Results of experiments and analysis also indicate that the pulse delay time, pulse width and the power ratio of pulse to rectangular waveform seriously influence the penetration when the pulsed wave is superimposed on a rectangular waveform.
基金This work was financially supported by the Ministry of Education,Science and Technological Development of the Republic of Serbia through Project Nos.ON174004 and ON172019the PhD fellowship of Slađana Laketić.
文摘The effects of picosecond Nd:YAG laser irradiation on chemical and morphological surface characteristics of the commercially pure titanium and Ti–13Nb–13Zr alloy in air and argon atmospheres were studied under different laser output energy values.During the interaction of laser irradiation with the investigated materials,a part of the energy was absorbed on the target surface,influencing surface modifications.Laser beam interaction with the target surface resulted in various morphological alterations,resulting in crater formation and the presence of microcracks and hydrodynamic structures.Moreover,different chemical changes were induced on the target materials’surfaces,resulting in the titanium oxide formation in the irradiation-affected area and consequently increasing the irradiation energy absorption.Given the high energy absorption at the site of interaction,the dimensions of the surface damaged area increased.Consequently,surface roughness increased.The appearance of surface oxides also led to the increased material hardness in the surface-modified area.Observed chemical and morphological changes were pronounced after laser irradiation of the Ti–13Nb–13Zr alloy surface.
基金Supported by the Natural Science Foundation of Shandong Province under Grant Nos ZR2015FM018 and ZR2014FM028the National Natural Science Foundation of China under Grant No 61475086
文摘A high-power passively Q-switched Nd：YAG laser operating at lll2nm with Cr4＋：yAO as a saturable absorber is demonstrated. Under 808 nm diode-direct pumping, the maximum average output power of 2.73 W is achieved at the pump power of 16.65 W, corresponding to an optical-to-optical conversion efficiency of 16.4%. At the same time, the pulse width, pulse repetition rate, single pulse energy and peak power are 27.2ns, 9 kHz, 303.3#3 and 11.2kW, respectively. As far as we know, the result gives the highest average output power at 1112nm generated by an 808 nm diode-end-pumped Nd：YAG laser.
基金supported by the Science Foundation of the Ministry of Science and Technology Malaysiathe Islamic Development Bank Jeddahsupport of the Universiti Teknologi Malaysia for this research work
文摘This study deals with Nd：YAG laser cutting nonmetallic materials, which is one of the most important and popular industrial applications of laser. The main theme is to evaluate the effects of Nd：YAG laser beam power besides work piece scanning speed. For approximate cutting depth, a theoretical study is conducted in terms of material property and cutting speed. Results show a nonlinear relation between the cutting depth and input energy. There is no significant effect of speed on cutting depth with the speed being larger than 30 mm/s. An extra energy is utilized in the deep cutting. It is inferred that as the laser power increases, cutting depth increases. The experimental outcomes are in good agreement with theoretical results. This analysis will provide a guideline for laser-based industry to select a suitable laser for cutting, scribing, trimming, engraving, and marking nonmetallic materials.
基金Supported by the Foundation of Shandong Province under Grant No J13LN28the National Natural Science Foundation of China under Grant No 11304184
文摘Performance of an LD-end-pumped passively Q-switched Nd： YA G/Cr4＋ ： YA G microchip laser operating at 1123 nm is studied. A maximum average output power of 517row with an optical-to-optical conversion efficiency of 12.6% and a slope efficiency of 25.8% is obtained under a pump power of 4.1 W. A minimum pulse width of 1.1 ns with a pulse repetition rate of 20.2kHz is obtained, and the corresponding pulse energy and peak power are 25.6μJ and 23.3kW, respectively. To our knowledge, the 23.3kW peak power is the highest among 1123nm lasers. Additionally, based on the 1123 nm laser, with LBO as the frequency doubler, a 288-mW green-yellow laser at 561 nm is successfully achieved.
基金the National Natural Science Foundation of China(Nos.61575166 and No.61675174).
文摘Exploiting a specially designed Fabry-Perot filter as output coupler,a continuous 1052 nm and 1061 nm dual-wavelength laser is realized.The threshold,slope efficiency and maximum power of the 1052 nm and 1061 nm dual-wavelength laser are 2.55 W,17.5%and 571 mW,respectively.The competition and coexistent relationships between 1052 nm,1061 nm and 1064 nm are analyzed.Involved non-degenerate Stark energy level structures are used to classify dual-wavelength lasers.According to this method,dual-wavelength lasers can be classified as different upper and lower non-degenerate Stark energy levels,the same upper but different lower Stark energy levels,different upper but the same lower Stark energy levels.Representative Nd:YAG dual-wavelength lasers are classified according to this criterion.It is found that the realization of front two type lasers is easy and that of third type lasers is challenging.This method can be used as a level of difficulty reference for the realization of dual-wavelength lasers.
文摘The main aim of this research is to optimize the tensile strength of laser welded FeCo-V alloy.A mathematicalrelationship was developed to predict tensile strength of the laser beam welded FeCo-V foils by incorporating process parameterssuch as lamping current,welding speed,pulse duration and focused position.The procedure was established to improve the weldstrength and increase the productivity.The results indicate that the pulse duration and welding speed have the greatest influence ontensile strength.The obtained results showed that the tensile strength of the weld joints increase as a function of increasing pulseduration reaching to a maximum at a pulse duration value of2.25ms.Moreover,the tensile strength of joints increases with decreasein welding speed reaching to a maximum at a welding speed of125mm/min.It has been shown that increase in pulse duration anddecrease in welding speed result in increased effective peak power density and hence formation of more resistant welds.At higherpulse durations and lower welding speeds,the tensile strength of weld joints decreases because of formation of solidificationmicrocracks in the fusion zone.
