共查询到19条相似文献,搜索用时 218 毫秒
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研究了激光椭偏率对基于光场感生电离(OFI)电子碰撞机制类镍氪(NLK)系统电离参数的影响。计算结果表明,激光椭偏率对NLK系统的电离速率、电离电子剩余能、各电荷态相对集居数随时间的变化以及初始电子能量分布等电离参数的影响较大,圆偏振激光场是实现NLK 32.8 nm X射线激光放大的最佳激励光场。理论计算表明,在圆偏振飞秒激光驱动下,实现NLK 32.8 nm X射线激光放大需要的最低激光强度为3.5×1016W/cm2,最高激光强度为1.6×1017W/cm2,实验估计的激光强度可能在5×1017W/cm2以上。 相似文献
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大气污染物SO2的光声探测 总被引:4,自引:2,他引:2
以波长为266nm的激光为激发光源,采用脉冲光声光谱技术,用自制的光声探测装置对SO2分子的光声吸收特性进行了实验研究,获得了室温、665Pa气压的实验条件下声音在SO2气体中的传播速度.通过测量光声信号随实验条件的变化发现,光声信号强度随激光能量的增加而增大,随缓冲气体压强升高而增大,缓冲气压增加到约2.66×104Pa时出现饱和现象.在标准大气压情况下,测量了痕量SO2气体的浓度,采用这套光声探测装置,SO2气体探测灵敏度可以达到9.1×10-6. 相似文献
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本文报道用 Nd-YAG脉冲激光辐照代替热合金化制备了性能良好的 P-InP/AuSb +AuZn + Au欧姆接触.利用激光合金所获得的接触电阻率8.6× 10~(-5)~Ω·cm~2优于另一部分样品热合金化的值1.6 ×10~(-4)Ω·cm~2.其表面形貌也比热合金化的好,俄歇电子能谱分析发现在界面附近明显形成了Zn的分布峰,使电子隧穿势垒的几率增大. 相似文献
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为了深入理解超短脉冲激光烧蚀金属的机理,特别是烧蚀过程中靶面电子发射带来的影响,本文分析了飞秒脉冲激光烧蚀金属的机理,并在此基础上建立了一维热传导双温模型,模型考虑了电子热导率、热容、电子-晶格耦合系数等参数随温度的变化,以及表面热电子发射和多光子电离导致靶面的能量损失。选择波长为 800 nm,FWHM为100 fs,峰值功率密度为1.2×1017 W/m2 的高斯型单脉冲激光辐照铜靶进行数值模拟。并对计算数据进行分析,结果表明:多光子电离所导致的电子发射比热电子发射要强,但是热电子发射持续的时间长;多光子电离导致的电子发射带走的靶面能量比较大,在分析飞秒烧蚀过程中不可忽略。 相似文献
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大气模式激光推进耦合系数的实验研究 总被引:10,自引:7,他引:10
为了研究大气压强对激光推进耦合系数的影响,设计了一座真空仓,利用真空泵系统控制仓内气压从4.6×103Pa到101.3×103Pa之间变化。采用单脉冲能量为20J的TEACO2激光器,对挂有光船模型的冲击摆进行大气模式激光推进耦合系数的测定。实验发现随着真空仓内气压的上升,冲量耦合系数逐渐增大,当气压值达到34.6×103Pa左右时,冲量耦合系数达到最大,随后伴同气压值的增加冲量耦合系数逐步下降。当入射激光单脉冲能量为10J时,冲量耦合系数的峰值处的气压值略有降低。从激光等离子体冲击波的角度对这一现象进行了初步的分析和解释,预测了能量对冲量耦合系数的峰值影响。 相似文献
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We demonstrate a photon counting laser ranging experiment with a four-channel single-photon detector (SPD). The multi-channel SPD improve the counting rate more than 4×107 cps, which makes possible for the distance measurement performed even in daylight. However, the time-correlated single-photon counting (TCSPC) technique cannot distill the signal easily while the fast moving targets are submersed in the strong background. We propose a dynamic TCSPC method for fast moving targets measurement by varying coincidence window in real time. In the experiment, we prove that targets with velocity of 5 km/s can be detected according to the method, while the echo rate is 20% with the background counts of more than 1.2×107 cps. 相似文献
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K. Sakai T. Yoshida K. Kuba Y. Kato Y. Ichioka 《Journal of Infrared, Millimeter and Terahertz Waves》1987,8(3):307-316
Methods based on the Stark effect are described for dither-free frequency stabilization of the optically pumped submm laser. The CO2 pump laser was stabilized using a Stark Lamb dip signal of the submm lasant in an external Stark cell. An estimated frequency stability (Δf/f) better than ±1.4×10?8, for one hour recording, was obtained by this method. The frequency of the submm laser was stabilized using the d.c. and a.c. Stark effects for a metal-dielectric rectangular waveguide laser. An estimated frequency stability of ±6×10?8 was obtained for 119 μm line of CH3OH laser for one hour recording. 相似文献
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V. A. Kukushkin 《Semiconductors》2008,42(7):794-799
A method of periodic short-term inversion for intersubband laser transitions in a quantum well with a repetition frequency of ~1 GHz and inversion retention time ~1 ps is suggested. The method is based on fast population of the upper transition level as a result of resonance tunneling of charge carriers from neighboring quantum wells as the electric field applied to the heterostructure is varied. As a consequence, the peak value of the population inversion can be as large, for example, as 8 × 1010 cm?2 for the transition corresponding to the wavelength λ ≈ 10 μm and 2 × 1010 cm?2 in the case of λ ≈ 25 μm. This method can be implemented at room temperature, which makes it attractive for fabrication of amplifiers of picosecond pulses for the middle and far infrared optical regions and the terahertz band. 相似文献
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采用能量密度为1.178×109W/cm2的XeCl准分子激光直接辐照高纯度的石墨靶,并同时采用辅助放电,在1×10-5Torr的真空环境中,于温度为80℃的Si(100)的基片上淀积出类金刚石薄膜,Raman光谱显示在1330cm-1处出现较强的散射峰值;对薄膜红外光谱进行测试,其光谱在2900cm-1处有吸收峰,表明所淀积的类金刚石薄膜含有C-H键,其H元素与C元素的比为45%.薄膜的电阻率为1.89×106Ω/cm,通过光吸收测得的该薄膜的能隙为1.55eV. 相似文献
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Asenic ions are implanted with doses of 5×10~(11)—5×10~(15)/cm~2 into LPCVD polysilicon films on SiO_2 isolating substrate.The polysilicon films have been recrystallized with CW Ar~+ laser before implantation.Electrical measurements show that the resistivity is lowered and the mobility is increased significantly at low doping concentration(~10~(17)As~+/cm~3).Plasma hydrogen annealing is performed on laser-recrystallized samples.The electrical characteristics of plasma hydrogen annealed samples are close to that of single crystalline silicon.It is found that the resistivity decreases from 1.2 Ω.cm to 0.45 Ω.cm,the mobility rises from 62 cm~2/V.s to 271 cm~2/V.s,the electrical activation energy reduces from 0.03 eV to -0.007 eV and the trapping state density at the grain boundary drops from 3.7×10~(11)/cm~2 to 1.7×10~(11)/cm~2.Based on the existing theoretical models for conduction in polysilicon, a new formula for large grain polysilicon has been proposed,with the help of which,a good agreement between theory and experimental results is achieved within the doping concentration range from 10~(16)/cm~3 to 10~(20)/cm~3. 相似文献