Catastrophic degradation of high power laser diodes is due to the generation of extended defects inside the active parts of the laser structure during the laser operation.The mechanism driving the degradation is stron...Catastrophic degradation of high power laser diodes is due to the generation of extended defects inside the active parts of the laser structure during the laser operation.The mechanism driving the degradation is strongly related to the existence of localized thermal stresses generated during the laser operation.These thermal stresses can overcome the yield strength of the materials forming the active part of the laser diode.Different factors contribute to reduce the laser power threshold for degradation.Among them the thermal transport across the laser structure constitutes a critical issue for the reliability of the device.展开更多
High laser-induced damage threshold and large aperture were focuses on the studies of high power laser coatings. This paper reports the research activities at our center. Several measures were developed for evaluating...High laser-induced damage threshold and large aperture were focuses on the studies of high power laser coatings. This paper reports the research activities at our center. Several measures were developed for evaluating characters of laser damage, including determination of laser induced damage threshold and detection of absorption based on surface thermal lensing technique. Defect was deemed to be the initial source of laser damage, and was the main factor restricting the laser damage resistance of optical coatings. The contribution of several kinds of typical defects to laser damage was analyzed, and some deposition measures were adopted to control and eliminate the origin of defect. Furthermore, some post-treatment methods were also employed to alleviate the influence of the defect and to improve the laser damage resistance. Correction mask was introduced to improve the thickness uniformity, and the thickness uniformity can be amended to less than 1% in the range of Φ650 mm. Preliminary investigation related to surface deformation was also conducted.展开更多
To improve the performance of double clad high power fibre lasers, inner cladding design plays a significant role. A triangular inner cladding and silica structure second cladding with large air holes go acquire high ...To improve the performance of double clad high power fibre lasers, inner cladding design plays a significant role. A triangular inner cladding and silica structure second cladding with large air holes go acquire high inner cladding numerical aperture are designed. Single mode and high power output of the fibre lasers need the double clad Yb doped fibre with large core. A fibre with annular refractive index distribution core and low numerical aperture to acquire a large mode area fibre core is designed and fabricated. Furthermore co-doping with aluminium （A1） has been used to improve the solubility of ytterbium （Yb） into silicate network, and the core absorption coefficients of two Yb doped fibres are compared with different A1 concentration experimentally.展开更多
Since the proof-of-principle demonstration of optical parametric amplification to efficiently amplify chirped laser pulses in 1992, optical parametric chirped pulse amplification（OPCPA） became the most promising met...Since the proof-of-principle demonstration of optical parametric amplification to efficiently amplify chirped laser pulses in 1992, optical parametric chirped pulse amplification（OPCPA） became the most promising method for the amplification of broadband optical pulses. In the meantime, we are witnessing an exciting progress in the development of powerful and ultrashort pulse laser systems that employ chirped pulse parametric amplifiers. The output power and pulse duration of these systems have ranged from a few gigawatts to hundreds of terawatts with a potential of tens of petawatts power level. Meanwhile, the output pulse duration based on optical parametric amplification has entered the range of fewoptical-cycle field. In this paper, we overview the basic principles, trends in development, and current state of the ultrashort and laser systems based on OPCPA, respectively.展开更多
There are many appearances in the literature of reliable observations of studying so-called “jets” and “sprites” - the discharges in the gigantic natural capacitor “Ionosphere-Earth” [1]. The volume of such a di...There are many appearances in the literature of reliable observations of studying so-called “jets” and “sprites” - the discharges in the gigantic natural capacitor “Ionosphere-Earth” [1]. The volume of such a discharge is approximately 5-10 thousand cubic kilometers and usually it appears above the surface of ocean. There are the cases also of above mentioned discharges on the ground. The value of the energy transferred to the earth can comprise to several terajoule. Events are accompanied by the emission of the waves of ultra-low frequency. Their study has the significant interest from many points of view. The essence of the observed irregular phenomena consists of the electromechanical conversion of the energy excesses of natural electricity into mechanical and thermal energy of cyclones, typhoons and other natural cataclysms. The ionosphere can retain only the specific quantity of energy. Otherwise, it discards the surpluses of electricity through the atmosphere or transforms them into the energy of storms, in that number and inside the Earth. By using the part of the natural electricity for useful purposes it is possible to govern the weather of planet. Causing the artificial breakdowns of the ionosphere it could be possible to arrange the discharge of the controlled aqueous sediments at the necessary points of the globe. It could be possible as well to attempt to regulate the climate of planet and to decrease the amplitudes of the magnetic storms, earthquakes and hurricanes.展开更多
During the last year the high power laser diodes jumped over the 1 kW level of CW power for a stack, and the commercial 1 cm bars reached 100 W output optical power at the standard wavelengths around 800 nm and 980 nm...During the last year the high power laser diodes jumped over the 1 kW level of CW power for a stack, and the commercial 1 cm bars reached 100 W output optical power at the standard wavelengths around 800 nm and 980 nm. The prices are reaching the industry acceptable levels. All Nd∶YAG and fiber industrial lasers manufacturers have developed kW prototypes. Those achievements have set new requirements for the power supplies manufactuers-high and stable output current, and possibilities for fast control of the driving current, keeping safe the expensive laser diode. The fast switching frequencies also allow long range free space communications and optical range finding. The high frequencies allow the design of a 3D laser radar with high resolution and other military applications. The prospects for direct laser diode micro machining are also attractive.展开更多
The 975 nm multimode diode lasers with high-order surface Bragg diffraction gratings have been simulated and calcu-lated using the 2D finite difference time domain(FDTD)algorithm and the scattering matrix method(SMM)....The 975 nm multimode diode lasers with high-order surface Bragg diffraction gratings have been simulated and calcu-lated using the 2D finite difference time domain(FDTD)algorithm and the scattering matrix method(SMM).The periods and etch depth of the grating parameters have been optimized.A board area laser diode(BA-LD)with high-order diffraction grat-ings has been designed and fabricated.At output powers up to 10.5 W,the measured spectral width of full width at half maxi-mum(FWHM)is less than 0.5 nm.The results demonstrate that the designed high-order surface gratings can effectively nar-row the spectral width of multimode semiconductor lasers at high output power.展开更多
We demonstrate a high power continuous-wave （CW） and acoustic-optically （AO） Q-switched 1314-nm laser with a diode-side-pumped Nd：YLF module. A maximum CW output power of 21.6 W is obtained with a diode pump powe...We demonstrate a high power continuous-wave （CW） and acoustic-optically （AO） Q-switched 1314-nm laser with a diode-side-pumped Nd：YLF module. A maximum CW output power of 21.6 W is obtained with a diode pump power of 180 W, corresponding to an optical-to-optical conversion efficiency of 12.0% and a slope efficiency of 16.1%. In the Q-switching operation, a highest pulse energy of 3.8 mJ is obtained at a pulse repetition rate of 1 kHz. The shortest pulse width and maximum single peak power are 101.9 ns and 37.3 kW, respectively.展开更多
Faced with the challenge of high energy ablation problems, especially for laser ablation, effective energy dissipation protective materials fabricate by efficient preparation method is a feasible solution. The Ni-grap...Faced with the challenge of high energy ablation problems, especially for laser ablation, effective energy dissipation protective materials fabricate by efficient preparation method is a feasible solution. The Ni-graphite/Si O2 coatings with different Ni content were prepared by plasma spraying method with optimized plasma spraying parameters. All coatings are pure without oxidation and dense. Their ablation behaviors were investigated by high power continuous wave laser. The results indicate that the Ni-graphite/Si O2 coating with appropriate Ni content could realize the purpose of energy consumption by endothermal reaction of graphite/Si O2 and reflection improvement. High Ni content will block the occurrence of endothermal reaction of graphite/Si O2 and increase the heat diffusion to interior part of coating, which can make the ablation situation of coating more serious.展开更多
The performances of high power Er/Yb codoped fiber linear cavity lasers are investigated numerically. The numerical analysis is based on the iterative solution of rate equations for population density of the Er/Yb ion...The performances of high power Er/Yb codoped fiber linear cavity lasers are investigated numerically. The numerical analysis is based on the iterative solution of rate equations for population density of the Er/Yb ions. The behaviors of co-pump and counter-pump methods are contrasted. Dependence of output power on input pump power, output reflectivity, operating wavelength and active fiber length is simulated, respectively. High conversion efficiency Er/Yb laser output is obtained in simulations and experiments.展开更多
The theoretical model of spatial noise passing through a spatial filter is established in high power laser system under the small signal approximation. The transmission characteristic for a noise signal passing throug...The theoretical model of spatial noise passing through a spatial filter is established in high power laser system under the small signal approximation. The transmission characteristic for a noise signal passing through spatial filters with different magnifications is analyzed by numerical simulation, according to the actual structure of the high power laser system. The results show that the spatial modulation period of low-frequency noise getting through the pinhole will be proportional to the magnification of the spatial filter. When the magnification is less than 1, the safe low-frequency noise will be extruded into the high-frequency region, which is the fast increasing part, and finally develops into the most dangerous part which can damage the optical devices. The conclusion of this research improves the relay imaging theory of a spatial filter and provides an important theoretical basis for a general design of high power laser systems.展开更多
9 to 12,April,2018 Suzhou,China International Symposium series on High Power Laser Science and Engineering,aiming at bringing together worldwide scientists and engineers working on high power laser and physics,is held...9 to 12,April,2018 Suzhou,China International Symposium series on High Power Laser Science and Engineering,aiming at bringing together worldwide scientists and engineers working on high power laser and physics,is held every two years since 2014.On behalf of the 3rd International Symposium on High Power Laser Science and Engineering(HPLSE2018),展开更多
A very highly efficient InGaAlAs/AlGaAs quantum-well structure was designed for 808 nm emission,and laser diode chips 390-μm-wide aperture and 2-mm-long cavity length were fabricated.Special pretreatment and passivat...A very highly efficient InGaAlAs/AlGaAs quantum-well structure was designed for 808 nm emission,and laser diode chips 390-μm-wide aperture and 2-mm-long cavity length were fabricated.Special pretreatment and passivation for the chip facets were performed to achieve improved reliability performance.The laser chips were p-side-down mounted on the AlN submount,and then tested at continuous wave(CW)operation with the heat-sink temperature setting to 25℃using a thermoelectric cooler(TEC).As high as 60.5%of the wall-plug efficiency(WPE)was achieved at the injection current of 11 A.The maximum output power of 30.1 W was obtained at 29.5 A when the TEC temperature was set to 12°C.Accelerated life-time test showed that the laser diodes had lifetimes of over 62111 h operating at rated power of 10 W.展开更多
We present the workflow of the design, realization and testing of deformable mirrors suitable for high power diode pumped solid-state lasers. It starts with the study of the aberration to be corrected, and then it con...We present the workflow of the design, realization and testing of deformable mirrors suitable for high power diode pumped solid-state lasers. It starts with the study of the aberration to be corrected, and then it continues with the design of the actuators position and characteristic. In this paper, we present and compare three deformable mirrors realized for multi-J level laser facilities. We show that with the same design concept it is possible to realize deformable mirrors for other types of lasers. As an example, we report the realization of a deformable mirror for femtosecond lasers and for a CW CO_2 laser.展开更多
An energy measurement system in a large-aperture high power laser experiment platform is introduced. The entire measurement system includes five calorimeters, which carry out the energy measurement of the fundamental ...An energy measurement system in a large-aperture high power laser experiment platform is introduced. The entire measurement system includes five calorimeters, which carry out the energy measurement of the fundamental frequency before the frequency conversion unit, remaining fundamental frequency, remaining second-harmonics, third-harmonics,as well as the energy balance measurement after the frequency conversion unit. Combinational indirect calibration and direct calibration are employed to calibrate the sampling coefficients of the calorimeters. The analysis of the data showed that, regarding the energy balance coefficients, combinational calibration approach gives a higher precision, and leads to an energy balance with 1%; and regarding the energy sampling coefficients for the various wavelengths after the frequency conversion, the results from direct and combinational calibration are consistent. The uncertainties for all energy sampling coefficients are within 3%, which guarantees the reliability of the energy measurement for the laser facility.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
Keyhole is one of the important phenomena in high-power laser welding process. By studying the keyhole characteristic and detecting the seam offset during high-power fiber laser welding, an infrared sensitive high-spe...Keyhole is one of the important phenomena in high-power laser welding process. By studying the keyhole characteristic and detecting the seam offset during high-power fiber laser welding, an infrared sensitive high-speed camera arranged off-axis orientation of laser beam was applied to capture the dynamic thermal images of a molten pool. The 304 austenitic stainless steel plate butt joint welding experiment with laser power 10 kW was carried out. Through analyzing the keyhole infrared image, the weld position was calculated. Least squares method was used to determine the actual weld position. Image filtering technique was used to process the keyhole image, and the keyhole centroid coordinate were calculated. Also, least squares method was used to fit the keyhole centroid curve equation and establish a nonlinear continuous model which described the deviation between keyhole centroid and weld seam. The heat accumulation effect affected by the infrared radiation was analyzed to determine whether the laser beam focus spot deviated from the desired welding seam. Experimental results showed that the keyhole centroid has related to the seam offset, and can reflect the welding quality.展开更多
Laser-solid interactions are highly suited as a potential source of high energy X-rays for nondestructive imaging.A bright,energetic X-ray pulse can be driven from a small source,making it ideal for high resolution X-...Laser-solid interactions are highly suited as a potential source of high energy X-rays for nondestructive imaging.A bright,energetic X-ray pulse can be driven from a small source,making it ideal for high resolution X-ray radiography.By limiting the lateral dimensions of the target we are able to confine the region over which X-rays are produced,enabling imaging with enhanced resolution and contrast.Using constrained targets we demonstrate experimentally a(20±3)μm X-ray source,improving the image quality compared to unconstrained foil targets.Modelling demonstrates that a larger sheath field envelope around the perimeter of the constrained targets increases the proportion of electron current that recirculates through the target,driving a brighter source of X-rays.展开更多
We observe the phenomenon of priority oscillation of the unexpected a-polarization in high-power Nd：YVO4 ring laser. The severe thermal lens of the a-polarized lasing, compared with the n-polarized lasing, is the onl...We observe the phenomenon of priority oscillation of the unexpected a-polarization in high-power Nd：YVO4 ring laser. The severe thermal lens of the a-polarized lasing, compared with the n-polarized lasing, is the only reason for the phenomenon. By designing a wedge Nd：YVO4 crystal as the gain medium, the unexpected a-polarization is completely suppressed in the entire range of pump powers, and the polarization stability of the expected zc-polarized output is enhanced. With the output power increasing from threshold to the maximum power, no a-polarization lasing is observed. As a result, 25.3 W of stable single-frequency laser output at 532 nm is experimentally demonstrated.展开更多
We present a new method that can be used to calculate pulse-front distortion by measuring the spectral interference of two point-diffraction fields in their overlapped district. We demonstrate, for the first time, the...We present a new method that can be used to calculate pulse-front distortion by measuring the spectral interference of two point-diffraction fields in their overlapped district. We demonstrate, for the first time, the measurement of the pulse-front distortion of the pulse from a complex multi-pass amplification system, which exists in almost all high-power laser systems, and obtain the irregular pulse-front distribution. The method presented does not need any reference light or assumption about the pulse-front distribution, and has an accuracy of several femtoseconds.展开更多
基金funded by the Spanish Government(MAT-2010-20441-C02)
文摘Catastrophic degradation of high power laser diodes is due to the generation of extended defects inside the active parts of the laser structure during the laser operation.The mechanism driving the degradation is strongly related to the existence of localized thermal stresses generated during the laser operation.These thermal stresses can overcome the yield strength of the materials forming the active part of the laser diode.Different factors contribute to reduce the laser power threshold for degradation.Among them the thermal transport across the laser structure constitutes a critical issue for the reliability of the device.
文摘High laser-induced damage threshold and large aperture were focuses on the studies of high power laser coatings. This paper reports the research activities at our center. Several measures were developed for evaluating characters of laser damage, including determination of laser induced damage threshold and detection of absorption based on surface thermal lensing technique. Defect was deemed to be the initial source of laser damage, and was the main factor restricting the laser damage resistance of optical coatings. The contribution of several kinds of typical defects to laser damage was analyzed, and some deposition measures were adopted to control and eliminate the origin of defect. Furthermore, some post-treatment methods were also employed to alleviate the influence of the defect and to improve the laser damage resistance. Correction mask was introduced to improve the thickness uniformity, and the thickness uniformity can be amended to less than 1% in the range of Φ650 mm. Preliminary investigation related to surface deformation was also conducted.
文摘To improve the performance of double clad high power fibre lasers, inner cladding design plays a significant role. A triangular inner cladding and silica structure second cladding with large air holes go acquire high inner cladding numerical aperture are designed. Single mode and high power output of the fibre lasers need the double clad Yb doped fibre with large core. A fibre with annular refractive index distribution core and low numerical aperture to acquire a large mode area fibre core is designed and fabricated. Furthermore co-doping with aluminium （A1） has been used to improve the solubility of ytterbium （Yb） into silicate network, and the core absorption coefficients of two Yb doped fibres are compared with different A1 concentration experimentally.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61378030 and 11127901)the National Basic Research Program of China(Grant No.2011CB808101)the International S&T Cooperation Program of China(Grant No.2011DFA11300)
文摘Since the proof-of-principle demonstration of optical parametric amplification to efficiently amplify chirped laser pulses in 1992, optical parametric chirped pulse amplification（OPCPA） became the most promising method for the amplification of broadband optical pulses. In the meantime, we are witnessing an exciting progress in the development of powerful and ultrashort pulse laser systems that employ chirped pulse parametric amplifiers. The output power and pulse duration of these systems have ranged from a few gigawatts to hundreds of terawatts with a potential of tens of petawatts power level. Meanwhile, the output pulse duration based on optical parametric amplification has entered the range of fewoptical-cycle field. In this paper, we overview the basic principles, trends in development, and current state of the ultrashort and laser systems based on OPCPA, respectively.
文摘There are many appearances in the literature of reliable observations of studying so-called “jets” and “sprites” - the discharges in the gigantic natural capacitor “Ionosphere-Earth” [1]. The volume of such a discharge is approximately 5-10 thousand cubic kilometers and usually it appears above the surface of ocean. There are the cases also of above mentioned discharges on the ground. The value of the energy transferred to the earth can comprise to several terajoule. Events are accompanied by the emission of the waves of ultra-low frequency. Their study has the significant interest from many points of view. The essence of the observed irregular phenomena consists of the electromechanical conversion of the energy excesses of natural electricity into mechanical and thermal energy of cyclones, typhoons and other natural cataclysms. The ionosphere can retain only the specific quantity of energy. Otherwise, it discards the surpluses of electricity through the atmosphere or transforms them into the energy of storms, in that number and inside the Earth. By using the part of the natural electricity for useful purposes it is possible to govern the weather of planet. Causing the artificial breakdowns of the ionosphere it could be possible to arrange the discharge of the controlled aqueous sediments at the necessary points of the globe. It could be possible as well to attempt to regulate the climate of planet and to decrease the amplitudes of the magnetic storms, earthquakes and hurricanes.
文摘During the last year the high power laser diodes jumped over the 1 kW level of CW power for a stack, and the commercial 1 cm bars reached 100 W output optical power at the standard wavelengths around 800 nm and 980 nm. The prices are reaching the industry acceptable levels. All Nd∶YAG and fiber industrial lasers manufacturers have developed kW prototypes. Those achievements have set new requirements for the power supplies manufactuers-high and stable output current, and possibilities for fast control of the driving current, keeping safe the expensive laser diode. The fast switching frequencies also allow long range free space communications and optical range finding. The high frequencies allow the design of a 3D laser radar with high resolution and other military applications. The prospects for direct laser diode micro machining are also attractive.
基金supported by the National Key R&D Program of China,No.2022YFB4601201.
文摘The 975 nm multimode diode lasers with high-order surface Bragg diffraction gratings have been simulated and calcu-lated using the 2D finite difference time domain(FDTD)algorithm and the scattering matrix method(SMM).The periods and etch depth of the grating parameters have been optimized.A board area laser diode(BA-LD)with high-order diffraction grat-ings has been designed and fabricated.At output powers up to 10.5 W,the measured spectral width of full width at half maxi-mum(FWHM)is less than 0.5 nm.The results demonstrate that the designed high-order surface gratings can effectively nar-row the spectral width of multimode semiconductor lasers at high output power.
基金supported by the National Natural Science Foundation of China(Nos.61275142,91022003,51021062,and 61308042)the China PostdoctoralScience Foundation(No.2013M531594)
文摘We demonstrate a high power continuous-wave （CW） and acoustic-optically （AO） Q-switched 1314-nm laser with a diode-side-pumped Nd：YLF module. A maximum CW output power of 21.6 W is obtained with a diode pump power of 180 W, corresponding to an optical-to-optical conversion efficiency of 12.0% and a slope efficiency of 16.1%. In the Q-switching operation, a highest pulse energy of 3.8 mJ is obtained at a pulse repetition rate of 1 kHz. The shortest pulse width and maximum single peak power are 101.9 ns and 37.3 kW, respectively.
基金financially supported by the National Natural Science Foundation of China(No.51302013)。
文摘Faced with the challenge of high energy ablation problems, especially for laser ablation, effective energy dissipation protective materials fabricate by efficient preparation method is a feasible solution. The Ni-graphite/Si O2 coatings with different Ni content were prepared by plasma spraying method with optimized plasma spraying parameters. All coatings are pure without oxidation and dense. Their ablation behaviors were investigated by high power continuous wave laser. The results indicate that the Ni-graphite/Si O2 coating with appropriate Ni content could realize the purpose of energy consumption by endothermal reaction of graphite/Si O2 and reflection improvement. High Ni content will block the occurrence of endothermal reaction of graphite/Si O2 and increase the heat diffusion to interior part of coating, which can make the ablation situation of coating more serious.
基金National Natural Science Foundation of China ( 60137010 ) Tianjin Key Project Foundation of China(033183611)
文摘The performances of high power Er/Yb codoped fiber linear cavity lasers are investigated numerically. The numerical analysis is based on the iterative solution of rate equations for population density of the Er/Yb ions. The behaviors of co-pump and counter-pump methods are contrasted. Dependence of output power on input pump power, output reflectivity, operating wavelength and active fiber length is simulated, respectively. High conversion efficiency Er/Yb laser output is obtained in simulations and experiments.
文摘The theoretical model of spatial noise passing through a spatial filter is established in high power laser system under the small signal approximation. The transmission characteristic for a noise signal passing through spatial filters with different magnifications is analyzed by numerical simulation, according to the actual structure of the high power laser system. The results show that the spatial modulation period of low-frequency noise getting through the pinhole will be proportional to the magnification of the spatial filter. When the magnification is less than 1, the safe low-frequency noise will be extruded into the high-frequency region, which is the fast increasing part, and finally develops into the most dangerous part which can damage the optical devices. The conclusion of this research improves the relay imaging theory of a spatial filter and provides an important theoretical basis for a general design of high power laser systems.
文摘9 to 12,April,2018 Suzhou,China International Symposium series on High Power Laser Science and Engineering,aiming at bringing together worldwide scientists and engineers working on high power laser and physics,is held every two years since 2014.On behalf of the 3rd International Symposium on High Power Laser Science and Engineering(HPLSE2018),
基金supported by the Natural Science Basic Research Plan in Shaanxi Province of China (No. 2018GY-005, No. 2017GY-065, No. 2017KJXX-72)
文摘A very highly efficient InGaAlAs/AlGaAs quantum-well structure was designed for 808 nm emission,and laser diode chips 390-μm-wide aperture and 2-mm-long cavity length were fabricated.Special pretreatment and passivation for the chip facets were performed to achieve improved reliability performance.The laser chips were p-side-down mounted on the AlN submount,and then tested at continuous wave(CW)operation with the heat-sink temperature setting to 25℃using a thermoelectric cooler(TEC).As high as 60.5%of the wall-plug efficiency(WPE)was achieved at the injection current of 11 A.The maximum output power of 30.1 W was obtained at 29.5 A when the TEC temperature was set to 12°C.Accelerated life-time test showed that the laser diodes had lifetimes of over 62111 h operating at rated power of 10 W.
基金co-financed by the European Regional Development Fundthe European Social Fund+1 种基金the state budget of the Czech Republic(project HiLASE:CZ.1.05/2.1.00/01.0027,project DPSSLasers:CZ.1.07/2.3.00/20.0143)partially supported by the grant RVO 68407700
文摘We present the workflow of the design, realization and testing of deformable mirrors suitable for high power diode pumped solid-state lasers. It starts with the study of the aberration to be corrected, and then it continues with the design of the actuators position and characteristic. In this paper, we present and compare three deformable mirrors realized for multi-J level laser facilities. We show that with the same design concept it is possible to realize deformable mirrors for other types of lasers. As an example, we report the realization of a deformable mirror for femtosecond lasers and for a CW CO_2 laser.
基金supported by the National Natural Science Foundation of China(No.61377102)
文摘An energy measurement system in a large-aperture high power laser experiment platform is introduced. The entire measurement system includes five calorimeters, which carry out the energy measurement of the fundamental frequency before the frequency conversion unit, remaining fundamental frequency, remaining second-harmonics, third-harmonics,as well as the energy balance measurement after the frequency conversion unit. Combinational indirect calibration and direct calibration are employed to calibrate the sampling coefficients of the calorimeters. The analysis of the data showed that, regarding the energy balance coefficients, combinational calibration approach gives a higher precision, and leads to an energy balance with 1%; and regarding the energy sampling coefficients for the various wavelengths after the frequency conversion, the results from direct and combinational calibration are consistent. The uncertainties for all energy sampling coefficients are within 3%, which guarantees the reliability of the energy measurement for the laser facility.
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Keyhole is one of the important phenomena in high-power laser welding process. By studying the keyhole characteristic and detecting the seam offset during high-power fiber laser welding, an infrared sensitive high-speed camera arranged off-axis orientation of laser beam was applied to capture the dynamic thermal images of a molten pool. The 304 austenitic stainless steel plate butt joint welding experiment with laser power 10 kW was carried out. Through analyzing the keyhole infrared image, the weld position was calculated. Least squares method was used to determine the actual weld position. Image filtering technique was used to process the keyhole image, and the keyhole centroid coordinate were calculated. Also, least squares method was used to fit the keyhole centroid curve equation and establish a nonlinear continuous model which described the deviation between keyhole centroid and weld seam. The heat accumulation effect affected by the infrared radiation was analyzed to determine whether the laser beam focus spot deviated from the desired welding seam. Experimental results showed that the keyhole centroid has related to the seam offset, and can reflect the welding quality.
基金supported by EPSRC grants EP/K022415/1and EP/R006202/1the STFC IPS grant ST/P000177/1
文摘Laser-solid interactions are highly suited as a potential source of high energy X-rays for nondestructive imaging.A bright,energetic X-ray pulse can be driven from a small source,making it ideal for high resolution X-ray radiography.By limiting the lateral dimensions of the target we are able to confine the region over which X-rays are produced,enabling imaging with enhanced resolution and contrast.Using constrained targets we demonstrate experimentally a(20±3)μm X-ray source,improving the image quality compared to unconstrained foil targets.Modelling demonstrates that a larger sheath field envelope around the perimeter of the constrained targets increases the proportion of electron current that recirculates through the target,driving a brighter source of X-rays.
基金supported by the National High Technology Research and Development Program of China(Grant No.2011AA030203)the National Basic Research Program of China(Grant No.2010CB923101)+1 种基金the National Natural Science Foundation of China(Grant No.61008001)the Natural Science Foundation of Shanxi Province,China(Grant No.2011021003-2)
文摘We observe the phenomenon of priority oscillation of the unexpected a-polarization in high-power Nd：YVO4 ring laser. The severe thermal lens of the a-polarized lasing, compared with the n-polarized lasing, is the only reason for the phenomenon. By designing a wedge Nd：YVO4 crystal as the gain medium, the unexpected a-polarization is completely suppressed in the entire range of pump powers, and the polarization stability of the expected zc-polarized output is enhanced. With the output power increasing from threshold to the maximum power, no a-polarization lasing is observed. As a result, 25.3 W of stable single-frequency laser output at 532 nm is experimentally demonstrated.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 10904132 and 11074225)the National Defense Science Technology Foundation of State Key Laboratory of High Temperature and Density Plasma Physics,China (Grant No. 9140C680604110C6805)
文摘We present a new method that can be used to calculate pulse-front distortion by measuring the spectral interference of two point-diffraction fields in their overlapped district. We demonstrate, for the first time, the measurement of the pulse-front distortion of the pulse from a complex multi-pass amplification system, which exists in almost all high-power laser systems, and obtain the irregular pulse-front distribution. The method presented does not need any reference light or assumption about the pulse-front distribution, and has an accuracy of several femtoseconds.
