Polished fused silica samples were etched for different durations by using hydrofluoric（HF） acid solution with HF concentrations in an ultrasonic field. Surface and subsurface polishing residues and molecular struct...Polished fused silica samples were etched for different durations by using hydrofluoric（HF） acid solution with HF concentrations in an ultrasonic field. Surface and subsurface polishing residues and molecular structure parameters before and after the etching process were characterized by using a fluorescence microscope and infrared（IR） spectrometer, respectively. The laser induced damage thresholds（LIDTs） of the samples were measured by using pulsed nanosecond laser with wavelength of 355 nm. The results showed that surface and subsurface polishing residues can be effectively reduced by the acid etching process, and the LIDTs of fused silica are significantly improved. The etching effects increased with the increase of the HF concentration from 5 wt.% to 40 wt.%. The amount of polishing residues decreased with the increase of the etching duration and then kept stable. Simultaneously, with the increase of the etching time, the mechanical strength and molecular structure were improved.展开更多
In this study,an excellent polarization optical crystal LiNa_(5)Mo_(9)O_(30) with wide transmission range and high laser damage threshold was researched in detail.The laser damage threshold of the LiNa_(5)Mo_(9)O_(30)...In this study,an excellent polarization optical crystal LiNa_(5)Mo_(9)O_(30) with wide transmission range and high laser damage threshold was researched in detail.The laser damage threshold of the LiNa_(5)Mo_(9)O_(30) crystal was measured to be 2.64GW/cm^(2),which was the highest among polarized optical crystals.The birefringence in the range of 0.435-5μm was larger than 0.14,while the wedge angle between 31.94°and 32.12°would satisfy the application in this waveband.The extinction ratio of the fabricated prism with the wedge angel of 31.09°was larger than 15,000:1.The results show that the LiNa_(5)Mo_(9)O_(30) prism is an excellent polarization device,especially in the mid-infrared range and high-power applications.展开更多
Nonlinear optical(NLO)crystals have been playing an increasingly important role in laser science and technology.The NLO crystals used in the middle infrared(mid-IR)region,compared with the NLO crystals in the other wa...Nonlinear optical(NLO)crystals have been playing an increasingly important role in laser science and technology.The NLO crystals used in the middle infrared(mid-IR)region,compared with the NLO crystals in the other wavelength regions,are still not good enough for the application of high-energy laser.The main defect is that their laser damage thresholds(LDT)are low.Chinese scientists have made a lot of important contributions to the UV and visible NLO crystals.In the last decade,they also did a lot of work on the mid-IR NLO materials.The main purpose of these researches is to increase the LDT and simultaneously balance the other properties.This paper presents a brief summary of their research progress in this topic on three types of materials:chalcogenides,oxides,and halides.The emphasis is put on the design strategy and quality control of the crystals.展开更多
The low laser induced damage threshold of the KH2PO4 crystal seriously restricts the output power of inertial confinement fusion.The micro-waviness on the KH2PO4 surface processed by single point diamond turning has a...The low laser induced damage threshold of the KH2PO4 crystal seriously restricts the output power of inertial confinement fusion.The micro-waviness on the KH2PO4 surface processed by single point diamond turning has a significant influence on the damage threshold.In this paper,the influence of micro-waviness on the damage threshold of the KH2PO4 crystal and the chief sources introducing the micro-waviness are analysed based on the combination of the Fourier modal theory and the power spectrum density method.Research results indicate that among the sub-wavinesses with different characteristic spatial frequencies there exists the most dangerous frequency which greatly reduces the damage threshold,although it may not occupy the largest proportion in the original surface.The experimental damage threshold is basically consistent with the theoretical calculation.For the processing parameters used,the leading frequency of micro-waviness which causes the damage threshold to decrease is between 350-1 μm-1 and 30-1 μm-1,especially between 90-1 μm-1 and 200-1 μm-1.Based on the classification study of the time frequencies of microwaviness,we find that the axial vibration of the spindle is the chief source introducing the micro-waviness,nearly all the leading frequencies are related to the practical spindle frequency（about 6.68 Hz,400 r/min） and a special middle frequency（between 1.029 Hz and 1.143 Hz）.展开更多
Rare earth doped B2O3-Al2O3-SiO2 glass （RExBAS, x=5, 10, 20; RE=La, Sm） were prepared by solid state reaction method. Optical transmission spectra of such glass were characterized by ultraviolet spectrometers, and 1...Rare earth doped B2O3-Al2O3-SiO2 glass （RExBAS, x=5, 10, 20; RE=La, Sm） were prepared by solid state reaction method. Optical transmission spectra of such glass were characterized by ultraviolet spectrometers, and 1064 nm laser induced damage performance was investigated through the method of ＂1-on-1＂. The results indicated that there was a strong absorptive peak near 1064 nm in SmxBAS glass, the peak was enhanced with increasing x. While LaxBAS glass was transparent to 1064 nm laser, at the same time, the results of laser induced damage showed that the anti-laser induced damage performance of such glass was strengthened with the addition of rare earth oxide. Furthermore, the laser induced damage threshold （LIDT） of SmxBAS glass was significantly higher than that of LaxBAS glass. Consequently, Sm^3＋ doping was favor in the improvement of anti-laser induced damage performance for BAS glass.展开更多
The laser-induced damage threshold(LIDT)of optical elements is a critical limitation in advancing nextgeneration spaceborne laser technologies.Transient mechanisms in multiple-pulse damage dynamics have been recognize...The laser-induced damage threshold(LIDT)of optical elements is a critical limitation in advancing nextgeneration spaceborne laser technologies.Transient mechanisms in multiple-pulse damage dynamics have been recognized,but significant gaps remain in understanding these processes.In this study,we introduce a practice time interval(Δt_(p))-dependent damage metric.Using a double-pulse double-probe experimental configuration,we systematically examine the double-pulse damage dynamics and relaxation process.The first pulse induces localized modifications that initiate a relaxation process,accumulating material damage caused by the subsequent pulse.Our results show that this relaxation lasts~500 ns for surface damage and is on a several millisecond scale for bulk damage.The second pulse induces more pronounced modifications and damage whenΔt_(p)is less than100 ns,dominated by nonlinear phenomena like multiphoton absorption due to temporally overlapping pulses.Conversely,forΔt_(p)>100 ns,thermal accumulation via phonon relaxation predominates.Additionally,the critical energy density for damage correlates positively with LIDT asΔt_(p)increases,reflecting the reduced thermal and mechanical stress influence.These findings highlight the dynamic competition between nonlinear and thermal effects in multiple-pulse laser interactions,providing practical strategies for designing optical components with high damage thresholds and developing high-performance optical systems.展开更多
In this paper,potassium dihydrogen phosphate（KDP） crystals were grown in the presence of a series of silicate（SiO32-） impurity concentrations via conventional temperature cooling and rapid growth methods,respectiv...In this paper,potassium dihydrogen phosphate（KDP） crystals were grown in the presence of a series of silicate（SiO32-） impurity concentrations via conventional temperature cooling and rapid growth methods,respectively.It revealed that the SiO32-impurity could lead to the decrease of transmittance at the region of ultraviolet band for pyramidal sectors and slightly increased the transmittance for prismatic sectors.SiO32-could enter into the crystal lattice and create lattice defects,which consequently increased the density of light scatter.The decrease of laser damage threshold was attributed to the lattice defects and the redundant electrons brought by the replacement of SiO32-at the PO43-position.展开更多
KH2PO4 （KDP） crystal with excellent optical properties is a very important element of inertial confinement fusion （ICF） device. However, KDP crystal surface micro-defects severely reduce the crystal laser damage t...KH2PO4 （KDP） crystal with excellent optical properties is a very important element of inertial confinement fusion （ICF） device. However, KDP crystal surface micro-defects severely reduce the crystal laser damage threshold, affecting the crystal service life. In this paper, Gaussian repaired pit is used to replace the crystal surface micro-defects, in order to improve the laser damage resistance of the KDP crystal with surface micro-defects. At first, the physical model of Gaussian repaired pit is built by Fourier model method, and the accuracy of the method is analyzed. It is found that the calculation error can be reduced by increasing the product of the width-period ratio and the truncation constant of the repaired pit. The calculation results about the physical model of Gaussian repaired pit show that the light intensity distribution within the crystal is symmetrical, and there are evidently enhanced light intensity regions in the crystal. Meanwhile, the maximum relative intensity inside the KDP crystal decreases gradually with the increase of the width of the Gaussian repaired pit. Secondly, the Gaussian repaired pits with different widths and the same depth of 20 μm are processed by micro-milling. Their surfaces are very smooth and present the ductile cutting state under the microscope. Finally, the laser damage threshold of the Gaussian repaired pits on the surface of the KDP crystal sample is measured by a 3 ω, 6-ns laser. The results showthat the maximum threshold of the Gaussian repaired pits is 3.12 J/cm2, which is 60% higher than the threshold of initial damage point, and the laser damage threshold increases with the increase of the width of the Gaussian repaired pit.展开更多
The KH2PO4 crystal is a key component in optical systems of inertial confinement fusion （ICF）. The microwaviness on a KH2PO4 crystal surface is strongly related to its damage threshold which is a key parameter for a...The KH2PO4 crystal is a key component in optical systems of inertial confinement fusion （ICF）. The microwaviness on a KH2PO4 crystal surface is strongly related to its damage threshold which is a key parameter for application. To study the laser induced damage mechanism caused by microwaviness, in this paper the near-field modulation properties of microwaviness to the incident wave are discussed by the Fourier modal method. Research results indicate that the microwaviness on the machined surface will distort the incident wave and thus lead to non-uniform distribution of the light intensity inside the crystal; in a common range of microwaviness amplitude, the light intensity modulation degree increases about 0.03 whenever the microwaviness amplitude increases 10 nm; 1 order diffraction efficiencies are the key factors responsible for light intensity modulation inside the crystal; the light intensity modulation is just around the microwaviness in the form of an evanescent wave, not inside the crystal when the microwaviness period is below 0.712μm; light intensity modulation degree has two extreme points in microwaviness periods of 1.064μm and 1.6μm, remains unchanged between periods of 3μm and 150μm, and descends above the period of 150μm to 920μm.展开更多
Large nonlinear optical(NLO)coefficient(d_(ij)),high laser damage threshold(LDT),and phase matching(PM)are crucial for the practical applications of IR NLO crystals.A great number of IR NLO materials with high dij hav...Large nonlinear optical(NLO)coefficient(d_(ij)),high laser damage threshold(LDT),and phase matching(PM)are crucial for the practical applications of IR NLO crystals.A great number of IR NLO materials with high dij have been explored,but many of them suffer from non-PM,which dramatically decreases their ultimate NLO output efficiencies.To settle this problem,we have developed a new strategy involving modulating normal dispersion via bandgap(E_(g))widening to achieve PM in this work.We synthesized successfully three new wide E_(g)(∼4.0 eV)IR NLO salt-inclusion sulfides[ABa_(3)Cl_(2)][Ga_(5)S_(10)](A=K,1;Rb,2;and Cs,3)with PM behaviors,mainly ascribed to the PM cut-off wavelength blue shift that originated from the wide Eg values,with less contribution from birefringence enhancement.All the compounds possessed large second-harmonic-generation(SHG)efficiency(∼1×AgGaS_(2))and hitherto the highest LDTs(188–200 MW/cm^(2),at 1.06μm,10 ns pulse width)for known chalcogenides with SHG efficiencies comparable to that of commercial silver gallium sulfide(AgGaS_(2))crystal.展开更多
基金Project supported by the China Postdoctoral Science Foundation(Grant No.2016M592709)the National Natural Science Foundation of China(Grant No.51535003)
文摘Polished fused silica samples were etched for different durations by using hydrofluoric（HF） acid solution with HF concentrations in an ultrasonic field. Surface and subsurface polishing residues and molecular structure parameters before and after the etching process were characterized by using a fluorescence microscope and infrared（IR） spectrometer, respectively. The laser induced damage thresholds（LIDTs） of the samples were measured by using pulsed nanosecond laser with wavelength of 355 nm. The results showed that surface and subsurface polishing residues can be effectively reduced by the acid etching process, and the LIDTs of fused silica are significantly improved. The etching effects increased with the increase of the HF concentration from 5 wt.% to 40 wt.%. The amount of polishing residues decreased with the increase of the etching duration and then kept stable. Simultaneously, with the increase of the etching time, the mechanical strength and molecular structure were improved.
基金This work was supported by the National Natural Science Foundation of China(Nos.51021062,62175129,50990061,and 50802054)973 Program of China(No.2010CB630702)+1 种基金China Postdoctoral Science Foundation(No.20110491600)Program of Introducing Talents of Disciplines to Universities in China(111 Program)(No.b06017).
文摘In this study,an excellent polarization optical crystal LiNa_(5)Mo_(9)O_(30) with wide transmission range and high laser damage threshold was researched in detail.The laser damage threshold of the LiNa_(5)Mo_(9)O_(30) crystal was measured to be 2.64GW/cm^(2),which was the highest among polarized optical crystals.The birefringence in the range of 0.435-5μm was larger than 0.14,while the wedge angle between 31.94°and 32.12°would satisfy the application in this waveband.The extinction ratio of the fabricated prism with the wedge angel of 31.09°was larger than 15,000:1.The results show that the LiNa_(5)Mo_(9)O_(30) prism is an excellent polarization device,especially in the mid-infrared range and high-power applications.
基金This work was supported by the National Basic Research Project of China(No.2010CB630701)the National Natural Science Foundation of China(No.91022036).
文摘Nonlinear optical(NLO)crystals have been playing an increasingly important role in laser science and technology.The NLO crystals used in the middle infrared(mid-IR)region,compared with the NLO crystals in the other wavelength regions,are still not good enough for the application of high-energy laser.The main defect is that their laser damage thresholds(LDT)are low.Chinese scientists have made a lot of important contributions to the UV and visible NLO crystals.In the last decade,they also did a lot of work on the mid-IR NLO materials.The main purpose of these researches is to increase the LDT and simultaneously balance the other properties.This paper presents a brief summary of their research progress in this topic on three types of materials:chalcogenides,oxides,and halides.The emphasis is put on the design strategy and quality control of the crystals.
基金Project supported by the National Natural Science Foundation of China (Grant No. 50875066)
文摘The low laser induced damage threshold of the KH2PO4 crystal seriously restricts the output power of inertial confinement fusion.The micro-waviness on the KH2PO4 surface processed by single point diamond turning has a significant influence on the damage threshold.In this paper,the influence of micro-waviness on the damage threshold of the KH2PO4 crystal and the chief sources introducing the micro-waviness are analysed based on the combination of the Fourier modal theory and the power spectrum density method.Research results indicate that among the sub-wavinesses with different characteristic spatial frequencies there exists the most dangerous frequency which greatly reduces the damage threshold,although it may not occupy the largest proportion in the original surface.The experimental damage threshold is basically consistent with the theoretical calculation.For the processing parameters used,the leading frequency of micro-waviness which causes the damage threshold to decrease is between 350-1 μm-1 and 30-1 μm-1,especially between 90-1 μm-1 and 200-1 μm-1.Based on the classification study of the time frequencies of microwaviness,we find that the axial vibration of the spindle is the chief source introducing the micro-waviness,nearly all the leading frequencies are related to the practical spindle frequency（about 6.68 Hz,400 r/min） and a special middle frequency（between 1.029 Hz and 1.143 Hz）.
基金the Natural Science Fund of Jangsu Provinence (BK2004121) Trans-Century Training Programme Foundation for the Talents by the Chinese Ministry of Education
文摘Rare earth doped B2O3-Al2O3-SiO2 glass （RExBAS, x=5, 10, 20; RE=La, Sm） were prepared by solid state reaction method. Optical transmission spectra of such glass were characterized by ultraviolet spectrometers, and 1064 nm laser induced damage performance was investigated through the method of ＂1-on-1＂. The results indicated that there was a strong absorptive peak near 1064 nm in SmxBAS glass, the peak was enhanced with increasing x. While LaxBAS glass was transparent to 1064 nm laser, at the same time, the results of laser induced damage showed that the anti-laser induced damage performance of such glass was strengthened with the addition of rare earth oxide. Furthermore, the laser induced damage threshold （LIDT） of SmxBAS glass was significantly higher than that of LaxBAS glass. Consequently, Sm^3＋ doping was favor in the improvement of anti-laser induced damage performance for BAS glass.
基金National Key Research and Development Program of China(2021YFB3601402)National Natural Science Foundation of China(61975153)。
文摘The laser-induced damage threshold(LIDT)of optical elements is a critical limitation in advancing nextgeneration spaceborne laser technologies.Transient mechanisms in multiple-pulse damage dynamics have been recognized,but significant gaps remain in understanding these processes.In this study,we introduce a practice time interval(Δt_(p))-dependent damage metric.Using a double-pulse double-probe experimental configuration,we systematically examine the double-pulse damage dynamics and relaxation process.The first pulse induces localized modifications that initiate a relaxation process,accumulating material damage caused by the subsequent pulse.Our results show that this relaxation lasts~500 ns for surface damage and is on a several millisecond scale for bulk damage.The second pulse induces more pronounced modifications and damage whenΔt_(p)is less than100 ns,dominated by nonlinear phenomena like multiphoton absorption due to temporally overlapping pulses.Conversely,forΔt_(p)>100 ns,thermal accumulation via phonon relaxation predominates.Additionally,the critical energy density for damage correlates positively with LIDT asΔt_(p)increases,reflecting the reduced thermal and mechanical stress influence.These findings highlight the dynamic competition between nonlinear and thermal effects in multiple-pulse laser interactions,providing practical strategies for designing optical components with high damage thresholds and developing high-performance optical systems.
基金supported by the National Natural Science Foundation of China (No. 50721002)
文摘In this paper,potassium dihydrogen phosphate（KDP） crystals were grown in the presence of a series of silicate（SiO32-） impurity concentrations via conventional temperature cooling and rapid growth methods,respectively.It revealed that the SiO32-impurity could lead to the decrease of transmittance at the region of ultraviolet band for pyramidal sectors and slightly increased the transmittance for prismatic sectors.SiO32-could enter into the crystal lattice and create lattice defects,which consequently increased the density of light scatter.The decrease of laser damage threshold was attributed to the lattice defects and the redundant electrons brought by the replacement of SiO32-at the PO43-position.
基金Project support by the National Natural Science Foundation of China(Grant No.51275113)the National Science and Technology Major Project of China(Grant No.2013ZX04006011-215)
文摘KH2PO4 （KDP） crystal with excellent optical properties is a very important element of inertial confinement fusion （ICF） device. However, KDP crystal surface micro-defects severely reduce the crystal laser damage threshold, affecting the crystal service life. In this paper, Gaussian repaired pit is used to replace the crystal surface micro-defects, in order to improve the laser damage resistance of the KDP crystal with surface micro-defects. At first, the physical model of Gaussian repaired pit is built by Fourier model method, and the accuracy of the method is analyzed. It is found that the calculation error can be reduced by increasing the product of the width-period ratio and the truncation constant of the repaired pit. The calculation results about the physical model of Gaussian repaired pit show that the light intensity distribution within the crystal is symmetrical, and there are evidently enhanced light intensity regions in the crystal. Meanwhile, the maximum relative intensity inside the KDP crystal decreases gradually with the increase of the width of the Gaussian repaired pit. Secondly, the Gaussian repaired pits with different widths and the same depth of 20 μm are processed by micro-milling. Their surfaces are very smooth and present the ductile cutting state under the microscope. Finally, the laser damage threshold of the Gaussian repaired pits on the surface of the KDP crystal sample is measured by a 3 ω, 6-ns laser. The results showthat the maximum threshold of the Gaussian repaired pits is 3.12 J/cm2, which is 60% higher than the threshold of initial damage point, and the laser damage threshold increases with the increase of the width of the Gaussian repaired pit.
基金Project supported by the National Natural Science Foundation of China (Grant No.50875066)the National High Technology Research and Development Program of China (Grant No.2009AA044305)
文摘The KH2PO4 crystal is a key component in optical systems of inertial confinement fusion （ICF）. The microwaviness on a KH2PO4 crystal surface is strongly related to its damage threshold which is a key parameter for application. To study the laser induced damage mechanism caused by microwaviness, in this paper the near-field modulation properties of microwaviness to the incident wave are discussed by the Fourier modal method. Research results indicate that the microwaviness on the machined surface will distort the incident wave and thus lead to non-uniform distribution of the light intensity inside the crystal; in a common range of microwaviness amplitude, the light intensity modulation degree increases about 0.03 whenever the microwaviness amplitude increases 10 nm; 1 order diffraction efficiencies are the key factors responsible for light intensity modulation inside the crystal; the light intensity modulation is just around the microwaviness in the form of an evanescent wave, not inside the crystal when the microwaviness period is below 0.712μm; light intensity modulation degree has two extreme points in microwaviness periods of 1.064μm and 1.6μm, remains unchanged between periods of 3μm and 150μm, and descends above the period of 150μm to 920μm.
基金supported by the NSF of China(21921001,21827813,and 21701176)the Strategic Priority Research Program of the CAS(XDB20010100 and YJKYYQ20180006)the NSF of Fujian Province(2018J05034).
文摘Large nonlinear optical(NLO)coefficient(d_(ij)),high laser damage threshold(LDT),and phase matching(PM)are crucial for the practical applications of IR NLO crystals.A great number of IR NLO materials with high dij have been explored,but many of them suffer from non-PM,which dramatically decreases their ultimate NLO output efficiencies.To settle this problem,we have developed a new strategy involving modulating normal dispersion via bandgap(E_(g))widening to achieve PM in this work.We synthesized successfully three new wide E_(g)(∼4.0 eV)IR NLO salt-inclusion sulfides[ABa_(3)Cl_(2)][Ga_(5)S_(10)](A=K,1;Rb,2;and Cs,3)with PM behaviors,mainly ascribed to the PM cut-off wavelength blue shift that originated from the wide Eg values,with less contribution from birefringence enhancement.All the compounds possessed large second-harmonic-generation(SHG)efficiency(∼1×AgGaS_(2))and hitherto the highest LDTs(188–200 MW/cm^(2),at 1.06μm,10 ns pulse width)for known chalcogenides with SHG efficiencies comparable to that of commercial silver gallium sulfide(AgGaS_(2))crystal.
