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We present the characteristics of bulk damage induced by the third harmonic of Nd:YAG laser irradiation in KDP and DKDP crystals. Bulk damage occurs as a few or a series of pinpoints consisting of a core and the deforming zone. The results of a 1-on-1 test reveal that the pinpoint size increases with incvreasing fluence, and the pinpoint density increases exponentially with increasing fluence. The results of an s-on-1 test indicate that the pinpoint density increases gradually with laser pulse number, but the size does not grow. These results are consistent with a model in which nanoabsorbers are assumed to exist in the crystal and the initiation of damage is determined by heating them to the critical temperature. 相似文献
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A thermal model is considered in order to better understand the mechanism of laser induced damage in KDP and DKDP crystals. We demonstrate that the expressions of pinpoint density and damage probability, predicted by the thermal model, are consistent with the experimental data. We also discuss the effect of particle interaction on the thermal model. 相似文献
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By testing a substantial number of tripler and z-cut KDP and DKDP crystals, we have observed that at 355nm, the laser induced damage threshold in the R-on-one test is higher than that in the one-on-one test. It is proved that laser conditioning is an efficient way to improve the damage resistance. The efficiency of laser conditioning becomes increasingly good with smaller ramping fluence steps. We have also found that the damage resistance of the z-cut crystal is higher than the triplet cut, and the pinpoint number is definitely less in the z-cut crystal. The reason for these observations is discussed. 相似文献
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By adding cubic and quartic phonon anharmonic interactions in the pseudospin lattice coupled mode (PLCM) model for KDP-type
crystals and using double-time temperature dependent Green's function method, expressions for soft mode frequency, dielectric
constant and dielectric tangent loss are obtained. Using model parameters given by Ganguliet al [9] the dielectric losses are calculated for KDP and DKDP crystals. In the microwave frequency range an increase in frequency
(1–35 GHz) is followed by an increase in dielectric tangent loss (1–35) at 98 K and (1–15) × 10−2 at 333 K for KDP and DKDP crystals respectively. The dielectric tangent loss decreases from 0.052 to 0.042 for KDP crystals
with increase in temperature from 130 to 170 K and for DKDP crystals it decreases from 0.0166 to 0.0074 with an increase in
temperature from 230–343 K in their paraelectric phases at 10 GHz. This shows Curie-Weiss behavior of the dielectric tangent
loss 相似文献
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The temperature dependence of muon interactions has been studied in ferroelectric KDP ( H2KPO4) and DKDP ( D2KPO4) using conventional μSR and muon spin resonance spectroscopy. In longitudinal field measurements, a fast relaxing component
and a slow relaxing component were observed. The slow relaxing component is attributed to diamagnetic muons. The muon spin
resonance measurements indicate that the fast relaxing component results from some muonium like species: either normal or
anomalous. In zero field and weak longitudinal field μSR (0–100 G), a remarkable peak in the fast relaxing component is observed
around 220 K in both KDP and DKDP. An additional feature is also seen around 300 K. The amplitude of the resonance measurement
has a broad minimum around 200 K which corresponds to the maximum in the relaxation rate in longitudinal field (100 G). The
temperature dependence of the muonium relaxation rate in KDP is almost identical to that of DKDP. The diamagnetic fraction
also shows almost no difference in relaxation rate or asymmetry for DKDP and KDP.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
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Characteristics of Laser-Induced Surface and Bulk Damage of Large-Aperture Deuterated Potassium Dihydrogen Phosphate at 351 nm
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《中国物理快报》2016,(2)
Deuterated potassium dihydrogen phosphate damage performance at 351 nm is studied on a large-aperture laser system.Bulk and rear-surface damage are initiated under the 3ω fluences of 6.7 J/cm~2 and 3J/cm~2,and show different growth characteristics under multiple laser irradiations with the fluence of 6 J/cm~2.The size and number of bulk damage keep unchanged once initiated.However,surface damage size also does not grow,while surface damage number increases linearly with laser shots.Different damage thresholds and growth behaviors suggest different formations of bulk and surface damage precursors.The cause of surface damage is supposed to be near-surface absorbing particles buried under the sol-gei coating. 相似文献
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抑制损伤发展的CO_2激光修复技术及机理研究 总被引:1,自引:1,他引:0
熔石英表面激光损伤发展问题一直制约着激光器的运行通量。采用CO2激光在线熔融修复损伤点,修复后形成一个光滑的高斯坑,去除了损伤点中的裂纹,平滑了凹凸不平的表面,并且在紫外脉冲激光作用下,修复斑再次产生损伤的阈值高于熔石英元件的损伤生长阈值。因此CO2熔融修复技术能有效地抑制损伤发展。通过分析CO2激光作用下熔石英表面的温度分布,讨论修复坑的形成过程,确定激光参数对修复效果的影响,为寻找最佳修复参数提供理论基础。同时利用原子力显微镜(AFM)、轮廓仪细致分析损伤点和修复斑的微细结构,采用有限差分时域方法计算损伤点和修复斑周围的光强分布,探索消除裂纹和平滑表面对抑制损伤生长的作用。 相似文献
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V. A. Abalmassov N. V. Surovtsev 《Bulletin of the Russian Academy of Sciences: Physics》2018,82(3):294-298
The temperature dependence of OH (OD) vibrations in KDP (DKDP) crystals is studied by Raman spectroscopy in different scattering geometries at temperatures from 30 to 299 K. The three lower frequencies from the five well-known high-frequency bands of OH (OD) vibrations soften upon an increase in the paraelectric phase temperature. This results from the softening of the corresponding harmonic potential upon an increase in the interatomic distance, and these frequencies are attributed to bending vibrations. The two higher frequencies of OH (OD) vibrations are virtually independent of temperature with a slight tendency to grow upon an increase in the paraelectric phase temperature. This is in better agreement with the complicated temperature dependence of the energy levels of the double-well potential along a hydrogen bond and allows these bands to be attributed to stretching OH (OD) vibrations. 相似文献
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B. D. Spitsyna E. N. Vasev G. S. Belikova N. P. Zaitseva A. M. Aronova 《Journal of Applied Spectroscopy》1991,55(3):919-923
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 55, No. 3, pp. 462–466, September, 1991. 相似文献
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在惯性约束聚变(ICF)终端光学组件(FOA)的精密装校过程中,超大超薄KDP晶体面形在重力作用下会发生畸变,从而导致晶体内部晶轴发生改变,进而由于波前相位失配而极大地降低高功率激光的频率转换效率。针对大口径薄型Ⅰ/Ⅱ类KDP晶体在非垂直放置状态下出现的附加面形问题,利用有限元分析软件,建立了具有不同初始面形的KDP晶体及其"杠杆式"夹持系统的模型,对晶体经夹持系统夹持后的附加面形分布进行了仿真计算,并讨论了支撑条上表面的加工误差类型及大小、晶体初始面形对KDP晶体附加面形的影响。研究结果表明:"杠杆式"夹持系统能有效改善大口径薄型KDP晶体因重力作用而引起的附加面形变化;晶体边缘部分的加工误差对KDP晶体附加面形有较大影响。 相似文献
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Technical Physics - The elastic and microplastic properties of large quasi-bulk GaN samples of two types, grown by hydride vapor-phase epitaxy, have been acoustically investigated. Samples of the... 相似文献
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用ICP-AES法测定KDP晶体及其培养液中微量的Fe、Cr、Mn、Ca、Mg、Al、Sr、Ba,并对KDP基体对被测元素谱线强度的影响进行考察。以Sc作内标,方法简便,可获得满意的分析结果。 相似文献
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MOVPE生长GaN的表面反应机理 总被引:1,自引:1,他引:0
利用量子化学的 DFT 理论,对 MOVPE 生长 GaN 薄膜的表面初始反应机理进行研究。通过计算GaCH3和NH3在GaN(0001)-Ga面的4种吸附位的能量曲线发现,GaCH3在各吸附位的吸附能差值不大,因此容易在表面迁移;而NH3在各吸附位的吸附能差值较大,最稳定吸附位为Top位,迁移到其他位置需要克服较大能垒。在此基础上,提出了以NH3和 GaCH3为表面生长基元,在GaN(0001)-Ga面连续生长,最终形成环状核心的二维生长机理:在环状核心形成过程中,第1个GaN核生长需要3个NH3和1个GaCH3,可表示为Ga( NH2)3。第2个GaN核生长可利用已有的1个N作为配位原子,故只需2个NH3和1个GaCH3。2个GaN核可表示为( NH2)2 Ga-NH-Ga( NH2)2。第3个GaN核生长可利用已有的2个N作为配位原子,故只需要1个NH3和1个GaCH3。3个GaN核构成环状核心,可表示为Ga3( NH)3( NH2)3。后续的生长将重复第2个核和第3个核的生长过程,从而实现GaN薄膜的连续台阶生长。 相似文献