P. Yang, Bosong Qin, Xiaoming Pan, Bingtao Sun, Wenwen Liu
{"title":"A theory model on multi-shot laser-induced damage of multilayer mirrors in nanosecond","authors":"P. Yang, Bosong Qin, Xiaoming Pan, Bingtao Sun, Wenwen Liu","doi":"10.1117/12.2539092","DOIUrl":"https://doi.org/10.1117/12.2539092","url":null,"abstract":"The accumulation effects in high-reflectivity (HR) HfO2/SiO2 coatings under laser irradiation at different laser wavelengths are investigated respectively. It was found that the multi-shot laser induced damage thresholds (LIDTs) were always lower than that under single-shot at 1064 nm and 532 nm because of \"fatigue effect\". And the evolution of LIDTs versus shot number, namely the optic lifetime was acquired. The previous analysis verified the accumulation damage mechanism was mainly due to the influence of newly created defects, namely, the laser-induced defects or intrinsic defects with irreversible changes under multiple pulse irradiations. Thus, a correlative theory model based on critical conduction band electron density is constructed to elucidate the experimental phenomena in nanosecond at different wavelengths with a 5Hz repetition rate. In particular, shallow trap (defect state) of varying absorption crosssection with irradiated shot numbers is used to simulate the material modification process under multiple pulse irradiations. It’s found that the absorption cross-section of the defect state at 532 nm is about one order of magnitude higher than that at 1064 nm, and defects at 532 nm need much less shot numbers to reach saturation with a higher growth factor.","PeriodicalId":197837,"journal":{"name":"SPIE/SIOM Pacific Rim Laser Damage","volume":"31 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-07-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123801484","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
S. Wang, X. Lei, J. Wang, Z. Liu, J. F. Zhang, Q. Xu
{"title":"Equivalent explosion simulation model for studying the laser-induced damage process of KDP crystal","authors":"S. Wang, X. Lei, J. Wang, Z. Liu, J. F. Zhang, Q. Xu","doi":"10.1117/12.2540018","DOIUrl":"https://doi.org/10.1117/12.2540018","url":null,"abstract":"When Potassium Dihydrogen Phosphate (KDP) crystal is irradiated by nanosecond laser with fluences exceeding its damage threshold, laser-induced damage occurs in the bulk or on the surfaces of crystal components. Such damage process is a multi-physical coupling process which is composed of energy deposition stage, temperature/pressure rising stage and subsequent micro explosion stage. So far, great efforts have been made in modeling the energy deposition and temperature/pressure rising stages of the damage process, but little attention has been paid on the subsequent micro explosion event. As a result, it is still impossible to reproduce the laser damage phenomena such as damage crater formation and shockwave propagation with the existing damage models. To address this concern, equivalent explosion simulation model for studying the laser-induced damage process of KDP crystals has been constructed by finite element method (FEM). According to the model, explosion energy leading to damage, formation of damage craters and propagation of shockwave can be obtained. Moreover, laser damage experiments combined with time-resolved techniques have been utilized to investigate the impact of laser fluences on the shockwave speed. Experiment results agree well with the simulated phenomenon, which has proved the validity of the simulation model.","PeriodicalId":197837,"journal":{"name":"SPIE/SIOM Pacific Rim Laser Damage","volume":"61 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-07-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123398503","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Xiaofeng Liu, Yuanan Zhao, Da-wei Li, Guohang Hu, J. Shao
{"title":"Laser damage characteristics of the YAG ceramics","authors":"Xiaofeng Liu, Yuanan Zhao, Da-wei Li, Guohang Hu, J. Shao","doi":"10.1117/12.2534736","DOIUrl":"https://doi.org/10.1117/12.2534736","url":null,"abstract":"Interest in the YAG (Y3Al5O12) transparent ceramics for laser systems has been increasing. As the laser gain medium in laser systems, especially in high power laser systems, the laser damage resistant of YAG ceramics are required to be evaluated. The laser damage characteristics of four ceramics with the dimensions of 30mm×15mm×3mm were investigated. It is found that the bulk laser induced damage thresholds (LIDTs) of the YAG ceramics are lower than their surface LIDTs. The bulk LIDTs are related with the transmissions of the YAG ceramics. The surface damage morphologies should be induced by the opens pores on the ceramic surface, which are left by surface manufacturing.","PeriodicalId":197837,"journal":{"name":"SPIE/SIOM Pacific Rim Laser Damage","volume":"11 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-07-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125610433","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Liping Peng, Yuanan Zhao, Xiaofeng Liu, Z. Cao, J. Shao, R. Hong, Chunxian Tao, Dawei Zhang, Xi Wang
{"title":"Investigation on damage process of indium tin oxide film induced by 1064nm quasi-CW laser","authors":"Liping Peng, Yuanan Zhao, Xiaofeng Liu, Z. Cao, J. Shao, R. Hong, Chunxian Tao, Dawei Zhang, Xi Wang","doi":"10.1117/12.2540821","DOIUrl":"https://doi.org/10.1117/12.2540821","url":null,"abstract":"Quasi-CW laser damage process of indium tin oxide (ITO) thin film was investigated. The ITO film with thickness of 300 nm was deposited on fused silica substrate by magnetron sputtering. Experiments were conducted on quasi-CW laser with wavelength of 1064 nm, and the test was executed in single shot test with radiation time of 60 s. The damage morphologies were observed via optical microscope and scanning electron microscope (SEM). The apparent damage started with change in color which the morphologies were visible to the naked eyes. With the power density higher than the laser induced damage threshold (LIDT), there were cracks in the center of the damage site. The temperature distribution of the ITO thin film was investigated based on the heat equation.","PeriodicalId":197837,"journal":{"name":"SPIE/SIOM Pacific Rim Laser Damage","volume":"14 1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-07-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123748414","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Q. Bai, Y. Li, R. Shen, K. Zhang, X. Miao, F. H. Zhang
{"title":"Molecular simulation and ablation property on the laser-induced metal surface","authors":"Q. Bai, Y. Li, R. Shen, K. Zhang, X. Miao, F. H. Zhang","doi":"10.1117/12.2539865","DOIUrl":"https://doi.org/10.1117/12.2539865","url":null,"abstract":"As a kind of typical material for mechanical structure, stainless steel is often adopted in the high-power laser facility. Iron elements in stainless steel may play an important role in resisting the effect of laser ablation. Laser ablation of stainless steel or aluminium alloy can also cause metal particle contamination in high-power laser facility. The ablation processes on iron surface under laser irradiation are investigated with molecular dynamics (MD) simulation combined with two-temperature model. The trajectories of atoms in each region of single crystal iron under laser irradiation are analyzed in terms of the interaction between laser and iron. The simulation results show that atoms absorbing different energy show the macroscopic characteristics of different phases of single crystal iron. Studies have also shown that single atom and clusters of atoms may have a backlash effect on the material and cause stress waves. The propagation of stress waves is also analyzed. It is shown that the velocity of the stress wave is about 6.094 km/s. Ablation threshold of single crystal iron is determined by the movement of surface atoms under different laser energy densities and the simulation results show that ablation threshold of single crystal iron under femtosecond laser is 0.18 J/cm2. Meanwhile, it is also found that the instantaneous loading of laser energy has a greater effect on material ablation. This study can underpin for investigating the damage and contamination of precision mechanical component with stainless steel under the effects of laser irradiation.","PeriodicalId":197837,"journal":{"name":"SPIE/SIOM Pacific Rim Laser Damage","volume":"55 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-07-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126639010","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
M. Mero, Li Wang, Weidong Chen, N. Ye, Ge Zhang, V. Petrov, Z. Heiner
{"title":"Laser-induced damage of nonlinear crystals in ultrafast, high-repetition-rate, mid-infrared optical parametric amplifiers pumped at 1 µm","authors":"M. Mero, Li Wang, Weidong Chen, N. Ye, Ge Zhang, V. Petrov, Z. Heiner","doi":"10.1117/12.2540125","DOIUrl":"https://doi.org/10.1117/12.2540125","url":null,"abstract":"The exceptional power scalability of Yb lasers has enabled the development of pulsed optical parametric amplifiers (OPA’s) operating at the short-wave edge of the mid-IR (MIR) with average powers beyond 10 W simultaneously providing peak powers in excess of 1 GW. Further wavelength extension into the longer-wave MIR is enabled by novel wide-bandgap non-oxide nonlinear crystals that can be pumped directly at 1 μm without detrimental one- and twophoton absorption of pump radiation. Eliminating the usual difference frequency generation step in producing MIR pulses above 5 μm could potentially increase the conversion efficiency of parametric down-conversion devices and enable a significant boost in the attainable average and peak power. Despite their utmost importance, material properties related to ultrafast laser-induced damage in nonlinear crystals are rarely investigated in the corresponding laser parameter range. In order to help unravel the complicated interplay of photorefractive effects, thermal lensing, and selffocusing/ defocusing affecting the beam quality and catastrophic breakdown threshold in MIR OPA’s, we present the nonlinear index of refraction at 1 μm of KTiOAsO4, LiGaS2, and BaGa4S7. The reported data provide crucial design parameters for the development of high-average-power MIR OPA’s. As examples, (i) a 100-kHz, 1.55/3.1 μm dual-beam OPA delivering multi-GW peak power in each beam and a total average power of 55 W and (ii) a 100-kHz, sub-100-fs, 1-μm-pumped OPA tunable in the 5.7-10.5-μm range are briefly presented.","PeriodicalId":197837,"journal":{"name":"SPIE/SIOM Pacific Rim Laser Damage","volume":"9 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-07-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114972949","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Zhigang Yuan, Yaguo Li, Du Wang, Ting Tan, H. Jin, Qinghua Zhang, Jian Wang, Qiao Xu
{"title":"Study on IR laser smoothing of ground surface on fused silica","authors":"Zhigang Yuan, Yaguo Li, Du Wang, Ting Tan, H. Jin, Qinghua Zhang, Jian Wang, Qiao Xu","doi":"10.1117/12.2539935","DOIUrl":"https://doi.org/10.1117/12.2539935","url":null,"abstract":"The application of fused silica in the field of High power laser requires that the formation of sub-surface damage be reduced in the process of grinding and polishing. Subsurface damage is unavoidable in traditional processing methods. Laser smoothing, as a non-contact polishing method, has attracted more and more attention in the surface treatment of fused silica. Laser smoothing is capable of producing smooth surface without incurring serious mechanical defects. Thus it is employed to polish fused silica in the hope of reducing mechanical defects on the optical components. In this paper, aiming at the ground surface of fused silica, the characteristics of mid-far infrared laser treatment and modification are studied. The surface smoothness under different laser power are studied, and the optimal laser power and action time for laser smoothing are obtained. This technology can reduce the ground surface roughness from above 100 nanometer to nanometer.","PeriodicalId":197837,"journal":{"name":"SPIE/SIOM Pacific Rim Laser Damage","volume":"690 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-07-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115118389","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
yelan Zhang, Yuyang Cheng, Kun Zhang, caiyu Li, W. Kong
{"title":"Broadband polarization beam splitter based on subwavelength grating in Terahertz","authors":"yelan Zhang, Yuyang Cheng, Kun Zhang, caiyu Li, W. Kong","doi":"10.1117/12.2535633","DOIUrl":"https://doi.org/10.1117/12.2535633","url":null,"abstract":"We design a broadband polarization beam splitter (PBS) operating in the terahertz (THz) communication band 0.1THz-1.2THz. The transmittance of the TM mode is larger than 95%, in the meanwhile, the extinction ratio can even reach 49dB. Considering the unavoidable deformation in grating fabrication, we also check the performance of the PBS based on trapeziform grating. Results show that increasing the duty cycle while the slope angle diminishing can effectively increase the TM mode transmittance and the extinction ratio, which can compensate the affection induced by the geometric deformation. This design may achieve some potential applications in THz manipulation system.","PeriodicalId":197837,"journal":{"name":"SPIE/SIOM Pacific Rim Laser Damage","volume":"12 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-07-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115621658","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Siying Chen, Baowei Li, He Chen, Yinchao Zhang, Pan Guo, Xunbao Rui, Ting Li
{"title":"A new method for air quality observation based on ultraviolet laser","authors":"Siying Chen, Baowei Li, He Chen, Yinchao Zhang, Pan Guo, Xunbao Rui, Ting Li","doi":"10.1117/12.2539999","DOIUrl":"https://doi.org/10.1117/12.2539999","url":null,"abstract":"A lidar based on UV laser is developed to observe air quality in Beijing. The initial laser wavelength is 1064 nm, and an emission wavelength of 355 nm is obtained after the second-harmonic generation and third-harmonic generation. The output energy is 30 mJ/pulse, and the pulse width is 7 ns. Echo signals are collected by a 304.8 mm diameter Newtonian telescope. With high-power ultraviolet laser excitation, the intensity of atmospheric pollutants is studied by the laserinduced fluorescence (LIF). The Mie scattering is detected simultaneously and both signals are detected by the photomultiplier tubes (PMT). The system is calibrated by a series of experiments. The aerosol extinction coefficient retrieved by Mie signal from this system agrees well with that from another lidar with a laser wavelength of 532 nm. The fluorescence efficiency of atmospheric pollutants are obtained by calculating the fluorescence-to-Mie ratio (FMR). The time and spatial resolution of the system are 5 s and 7.5 m, respectively. The continuous change of air quality over a period of time is studied by the mean value of FMR. Many observations are carried out under different air quality conditions, and the experimental results are in good agreement with the results of the ground observation station. In summary, this method based on UV laser is feasible in the field of atmospheric remote sensing and have potential applications in the field of air quality monitoring.","PeriodicalId":197837,"journal":{"name":"SPIE/SIOM Pacific Rim Laser Damage","volume":"82 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-07-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123430034","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Haodong Ma, Yuanan Zhao, Yuchen Shao, C. Li, Jian Sun, J. Shao
{"title":"The fatigue effect of femtosecond laser-induced damage in high-reflective coatings at low repetition rate","authors":"Haodong Ma, Yuanan Zhao, Yuchen Shao, C. Li, Jian Sun, J. Shao","doi":"10.1117/12.2539749","DOIUrl":"https://doi.org/10.1117/12.2539749","url":null,"abstract":"This work is dedicated to the study of fatigue effects upon femtosecond laser-induced damage of Ta2O5/HfO2/SiO2 highreflective coatings irradiated by pulse train at 1Hz (65 fs, 800 nm). Upon on comparative measurements of different pulse numbers involving between 10 and 300 pulses, laser-induced damage threshold (LIDT) decreases and the multipulse LIDT decreased to the level of 70~75% of the single pulse LIDT. In addition, we found that the probability of damage performs an increasing trend with the number of pulse increases when the coating is irradiated with the same fluence. The evolution of LIDT and 100% damage probability threshold under multipulse irradiations revealed that fatigue effects were affected by both laser fluence and shot numbers. The deep defects play an important role in the multi-shot mode. A correlative theory model based on critical conduction band electron density is constructed to elucidate the experimental phenomena.","PeriodicalId":197837,"journal":{"name":"SPIE/SIOM Pacific Rim Laser Damage","volume":"11063 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2019-07-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130104664","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}