Based on the effective structure of the self-mixing interference effects,a general model for the self-mixing interference effects in the LD pumped solid-state laser has been established for the first time.The numerica...Based on the effective structure of the self-mixing interference effects,a general model for the self-mixing interference effects in the LD pumped solid-state laser has been established for the first time.The numerical simulation of the self-mixing interference signal has been done,the results show that when the external cavity length is integral times of 1/2,1/3,2/3,1/4,3/4 of the effective cavity length,the intensity of the self-mixing interference signals reach maximum in value.While that of single mode laser is integral times of half of the effective cavity length,the measuring precision of displacement of single mode laser is λ/2.A conclusion can be drawn from the above results that the measuring precision of displacement of multi-mode laser is higher than that of single mode laser.展开更多
Optical memory effect-based speckle-correlated technology has been developed for reconstructing hidden objectsfrom disordered speckle patterns,achieving imaging through scattering layers.However,the lighting efficienc...Optical memory effect-based speckle-correlated technology has been developed for reconstructing hidden objectsfrom disordered speckle patterns,achieving imaging through scattering layers.However,the lighting efficiency and fieldof view of existing speckle-correlated imaging systems are limited.Here,a near-infrared low spatial coherence fiberrandom laser illumination method is proposed to address the above limitations.Through the utilization of random Rayleighscattering within dispersion-shifted fibers to provide feedback,coupled with stimulated Raman scattering for amplification,a near-infrared fiber random laser exhibiting a high spectral density and extremely low spatial coherence is generated.Based on the designed fiber random laser,speckle-correlated imaging through scattering layers is achieved,with highlighting efficiency and a large imaging field of view.This work improves the performance of speckle-correlated imagingand enriches the research on imaging through scattering medium.展开更多
The intrinsic features involving a circularly symmetric beam profile with low divergence, planar geometry as well as the increasingly enhanced power of vertical-cavity surface-emitting lasers （VCSELs） have made the ...The intrinsic features involving a circularly symmetric beam profile with low divergence, planar geometry as well as the increasingly enhanced power of vertical-cavity surface-emitting lasers （VCSELs） have made the VCSEL a promising pump source in direct end bonding to a solid-state laser medium to form the minimized, on-wafer integrated laser system. This scheme will generate a surface contact pump configuration and thus additional end thermal coupling to the laser medium through the joint interface of both materials, apart from pump beam heating. This paper analytically models temperature distributions in both VCSEL and the laser medium from the end thermal coupling regarding surface contact pump configuration using a top-emitting VCSEL as the pump source for the first time. The analytical solutions are derived by introducing relative temperature and mean temperature expressions. The results show that the end contact heating by the VCSEL could lead to considerable temperature variations associated with thermal phase shift and thermal lensing in the laser medium. However, if the central temperature of the interface is increased by less than 20 K, the end contact heating does not have a significant thermal influence on the laser medium. In this case, the thermal effect should be dominated by pump beam heating. This work provides useful analytical results for further analysis of hybrid thermal effects on those lasers pumped by a direct VCSEL bond.展开更多
A high-power cw all-solid-state Nd：GdVO4 laser operating at 88Onto is reported. The laser consists of a low doped level Nd：GdV04 crystal dual-end-pumped by two high-power diode lasers and a compact negative confocM ...A high-power cw all-solid-state Nd：GdVO4 laser operating at 88Onto is reported. The laser consists of a low doped level Nd：GdV04 crystal dual-end-pumped by two high-power diode lasers and a compact negative confocM unstable-stable hybrid resonator. At an incident pump power of 820 W, a maximum cw output of 240 W at 1064nm is obtained. The optical-to-optical efficiency and Mope efficiency are 40.7% and 53.2%, respectively. The M2 factors in the unstable direction and in the stable direction are 4.38 and 5.44, respectively.展开更多
In order to control the ferrite and austenite percentage in duplex stainless steel welding, many researchers try to change the laser welding parameters and cooling medium, but ignore to study the influence of heat sin...In order to control the ferrite and austenite percentage in duplex stainless steel welding, many researchers try to change the laser welding parameters and cooling medium, but ignore to study the influence of heat sink effect on weld strength. In this work, the effect of aluminium heat sink and varying cooling medium on the laser welding of duplex stainless steel (DSS) 2205 is studied. The 2 mm thick DSS sheets welded with pulsed Nd: YAG laser welding machine by varying the cooling medium (air and oil) and an aluminium plate used as a heat sink. The welded specimens tested for tensile strength, micro-hardness, distortion, microstructure and radiography analysis. The faster cooling rate in the oil quenching process enhances the ferrite percentage compared with air-cooled samples. But the faster cooling rate in oil quenching leads to more distortion and using aluminium as a heat sink influenced positively the distortion to a small extent. The lower cooling rate in air quenching leads to a higher tensile strength of the welded specimen. The objective of this work is to analyse experimentally the effect of cooling medium and heat sink in the mechanical and metallurgical properties of laser welded duplex stainless steel.展开更多
We present a laser-diode-pumped passively mode-locked femtosecond disordered crystal laser by using Nd：CaGdAI04 （Nd：CGA） as the gain medium. With a pair of SF6 prisms to control the dispersion compensation, laser ...We present a laser-diode-pumped passively mode-locked femtosecond disordered crystal laser by using Nd：CaGdAI04 （Nd：CGA） as the gain medium. With a pair of SF6 prisms to control the dispersion compensation, laser pulses as short as 850fs at 1079nm are obtained with a repetition rate of 124.6 MHz. The measured threshold pump power is 1.45 W. A maximum average output power of 122mW is obtained under the pump power of 5.9 W. These results show that Nd：CGA could be a promising laser medium for generating femtosecond ultrashort pulse at about 1 μm.展开更多
After considering Kerr nonlinear effect, group velocity dispersion of host and gain distribution of active particle in laser amplifying medium, a basic equation describing propagation of the coupling optical pulse und...After considering Kerr nonlinear effect, group velocity dispersion of host and gain distribution of active particle in laser amplifying medium, a basic equation describing propagation of the coupling optical pulse under the multi-photon nonlinear Compton scattering in the laser amplifying medium has been deduced. Besides, the profile and power spectrum of a picosecond-level super-Gaussian coupling pulse in the laser amplifying medium have been discussed when its central frequency coincides with the gain peak frequency of the laser amplifying medium.展开更多
A direct Kerr-lens mode-locked Tm:LuYO_(3)ceramic laser without the aid of any mode-locked starting element is reported for the first time. A pulse duration as short as 259 fs and a maximum average output power of 326...A direct Kerr-lens mode-locked Tm:LuYO_(3)ceramic laser without the aid of any mode-locked starting element is reported for the first time. A pulse duration as short as 259 fs and a maximum average output power of 326 m W are obtained at a repetition rate of 97.1 MHz. The corresponding optical spectrum centered at 2053 nm exhibits a bandwidth of 19.8 nm,which indicates the presence of nearly Fourier transform-limited pulses. Such a Kerr-lens mode-locked Tm:LuYO_(3)ceramic laser is a promising ultrashort pulse source, with both the excellent laser characteristics of Tm:LuYO3and the high-power 790 nm laser diode pumping scheme.展开更多
Stable,efficient and high color rendering index all-inorganic color converters are urgently demanded for white laser diodes.Phosphor-in-glass(PiG),possessing the advantages of phosphors excellent quantum efficiency as...Stable,efficient and high color rendering index all-inorganic color converters are urgently demanded for white laser diodes.Phosphor-in-glass(PiG),possessing the advantages of phosphors excellent quantum efficiency as well as favorable chemical and thermal stability of glass,has attracted widespread attention.There have been only very few reports of Y_(1.31)Ce_(0.09)Gd_(1.6)Al_(5)O_(12)(Ce:GdYAG)PiG for solid-state laser light-ing.Herein,a series of Ce:GdYAG PiG samples are fabricated by a simple solid-state sintering method.Impressively,the supreme internal quantum efficiency of as-prepared PiG is 91%,which is very close to original phosphors(95%).Furthermore,PiG exhibits a high thermal conductivity(1.844 W m^(−1)K^(−1))and a maximum transparency(62%).Remarkably,by changing the concentration of phosphors and the thickness of PiG samples,a luminous efficacy of 163.5 lm/W,high color rendering index of 74.8 and low correlated color temperature of 4806.8 K are achieved under blue laser irradiation.These results indicate that the Ce:GdYAG PiG samples have shown tremendous application foreground as all-inorganic color converter for solid-state laser lighting.展开更多
文摘Based on the effective structure of the self-mixing interference effects,a general model for the self-mixing interference effects in the LD pumped solid-state laser has been established for the first time.The numerical simulation of the self-mixing interference signal has been done,the results show that when the external cavity length is integral times of 1/2,1/3,2/3,1/4,3/4 of the effective cavity length,the intensity of the self-mixing interference signals reach maximum in value.While that of single mode laser is integral times of half of the effective cavity length,the measuring precision of displacement of single mode laser is λ/2.A conclusion can be drawn from the above results that the measuring precision of displacement of multi-mode laser is higher than that of single mode laser.
基金supported by the National Natural Science Foundation of China(Grant Nos.62375040 and 11974071)the Sichuan Science and Technology Program(Grant Nos.2022ZYD0108 and 2023JDRC0030).
文摘Optical memory effect-based speckle-correlated technology has been developed for reconstructing hidden objectsfrom disordered speckle patterns,achieving imaging through scattering layers.However,the lighting efficiency and fieldof view of existing speckle-correlated imaging systems are limited.Here,a near-infrared low spatial coherence fiberrandom laser illumination method is proposed to address the above limitations.Through the utilization of random Rayleighscattering within dispersion-shifted fibers to provide feedback,coupled with stimulated Raman scattering for amplification,a near-infrared fiber random laser exhibiting a high spectral density and extremely low spatial coherence is generated.Based on the designed fiber random laser,speckle-correlated imaging through scattering layers is achieved,with highlighting efficiency and a large imaging field of view.This work improves the performance of speckle-correlated imagingand enriches the research on imaging through scattering medium.
文摘The intrinsic features involving a circularly symmetric beam profile with low divergence, planar geometry as well as the increasingly enhanced power of vertical-cavity surface-emitting lasers （VCSELs） have made the VCSEL a promising pump source in direct end bonding to a solid-state laser medium to form the minimized, on-wafer integrated laser system. This scheme will generate a surface contact pump configuration and thus additional end thermal coupling to the laser medium through the joint interface of both materials, apart from pump beam heating. This paper analytically models temperature distributions in both VCSEL and the laser medium from the end thermal coupling regarding surface contact pump configuration using a top-emitting VCSEL as the pump source for the first time. The analytical solutions are derived by introducing relative temperature and mean temperature expressions. The results show that the end contact heating by the VCSEL could lead to considerable temperature variations associated with thermal phase shift and thermal lensing in the laser medium. However, if the central temperature of the interface is increased by less than 20 K, the end contact heating does not have a significant thermal influence on the laser medium. In this case, the thermal effect should be dominated by pump beam heating. This work provides useful analytical results for further analysis of hybrid thermal effects on those lasers pumped by a direct VCSEL bond.
文摘A high-power cw all-solid-state Nd：GdVO4 laser operating at 88Onto is reported. The laser consists of a low doped level Nd：GdV04 crystal dual-end-pumped by two high-power diode lasers and a compact negative confocM unstable-stable hybrid resonator. At an incident pump power of 820 W, a maximum cw output of 240 W at 1064nm is obtained. The optical-to-optical efficiency and Mope efficiency are 40.7% and 53.2%, respectively. The M2 factors in the unstable direction and in the stable direction are 4.38 and 5.44, respectively.
文摘In order to control the ferrite and austenite percentage in duplex stainless steel welding, many researchers try to change the laser welding parameters and cooling medium, but ignore to study the influence of heat sink effect on weld strength. In this work, the effect of aluminium heat sink and varying cooling medium on the laser welding of duplex stainless steel (DSS) 2205 is studied. The 2 mm thick DSS sheets welded with pulsed Nd: YAG laser welding machine by varying the cooling medium (air and oil) and an aluminium plate used as a heat sink. The welded specimens tested for tensile strength, micro-hardness, distortion, microstructure and radiography analysis. The faster cooling rate in the oil quenching process enhances the ferrite percentage compared with air-cooled samples. But the faster cooling rate in oil quenching leads to more distortion and using aluminium as a heat sink influenced positively the distortion to a small extent. The lower cooling rate in air quenching leads to a higher tensile strength of the welded specimen. The objective of this work is to analyse experimentally the effect of cooling medium and heat sink in the mechanical and metallurgical properties of laser welded duplex stainless steel.
基金Supported by the National Key Basic Research Program of China under Grant No 2013CB922402the International Joint Research Program,and the National Natural Science Foundation of China under Grant Nos 61210017 and 11434016
文摘We present a laser-diode-pumped passively mode-locked femtosecond disordered crystal laser by using Nd：CaGdAI04 （Nd：CGA） as the gain medium. With a pair of SF6 prisms to control the dispersion compensation, laser pulses as short as 850fs at 1079nm are obtained with a repetition rate of 124.6 MHz. The measured threshold pump power is 1.45 W. A maximum average output power of 122mW is obtained under the pump power of 5.9 W. These results show that Nd：CGA could be a promising laser medium for generating femtosecond ultrashort pulse at about 1 μm.
文摘After considering Kerr nonlinear effect, group velocity dispersion of host and gain distribution of active particle in laser amplifying medium, a basic equation describing propagation of the coupling optical pulse under the multi-photon nonlinear Compton scattering in the laser amplifying medium has been deduced. Besides, the profile and power spectrum of a picosecond-level super-Gaussian coupling pulse in the laser amplifying medium have been discussed when its central frequency coincides with the gain peak frequency of the laser amplifying medium.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 62165012 and 61665010)Key research and development projects in Gansu Province (Grant No. 21YFIGE300)+5 种基金Gansu Province College Industry Support Plan Project (Grant Nos. 2020C-23 and 2022CYZC-59)Department of Education of Gansu Province: The Education Project of Open Competition for the Best Candidates (Grant No. 2021jyjbgs-06)Gansu Provincial University Innovation Fund Project (Grant No. 2021B-190)Qinzhou District Science and Technology Plan Project (Grant No. 2021-SHFZG1442)Gansu Province College Young Doctor Support Project (Grant No. 2023QB-013)Gansu Province Excellent Graduate Innovation Star Project (Grant No. 2022CXZX796)。
文摘A direct Kerr-lens mode-locked Tm:LuYO_(3)ceramic laser without the aid of any mode-locked starting element is reported for the first time. A pulse duration as short as 259 fs and a maximum average output power of 326 m W are obtained at a repetition rate of 97.1 MHz. The corresponding optical spectrum centered at 2053 nm exhibits a bandwidth of 19.8 nm,which indicates the presence of nearly Fourier transform-limited pulses. Such a Kerr-lens mode-locked Tm:LuYO_(3)ceramic laser is a promising ultrashort pulse source, with both the excellent laser characteristics of Tm:LuYO3and the high-power 790 nm laser diode pumping scheme.
基金supported by the Key Research and Development Project in Zhejiang Province(No.2021C01024).
文摘Stable,efficient and high color rendering index all-inorganic color converters are urgently demanded for white laser diodes.Phosphor-in-glass(PiG),possessing the advantages of phosphors excellent quantum efficiency as well as favorable chemical and thermal stability of glass,has attracted widespread attention.There have been only very few reports of Y_(1.31)Ce_(0.09)Gd_(1.6)Al_(5)O_(12)(Ce:GdYAG)PiG for solid-state laser light-ing.Herein,a series of Ce:GdYAG PiG samples are fabricated by a simple solid-state sintering method.Impressively,the supreme internal quantum efficiency of as-prepared PiG is 91%,which is very close to original phosphors(95%).Furthermore,PiG exhibits a high thermal conductivity(1.844 W m^(−1)K^(−1))and a maximum transparency(62%).Remarkably,by changing the concentration of phosphors and the thickness of PiG samples,a luminous efficacy of 163.5 lm/W,high color rendering index of 74.8 and low correlated color temperature of 4806.8 K are achieved under blue laser irradiation.These results indicate that the Ce:GdYAG PiG samples have shown tremendous application foreground as all-inorganic color converter for solid-state laser lighting.
