不同激光脉冲驱动的尾场中正电子加速的研究

为了研究在激光驱动的尾场中被加速正电子的动能,采用数值模拟方法,得到了非对称sine脉冲、flat-top脉冲和Gaussian脉冲驱动的尾场中被加速的正电子的能量。结果表明,非对称sine脉冲驱动尾场中正电子得到的能量比flat-top脉冲和Gaussian脉冲驱动尾场中得到的能量高一些。     

对称和非对称激光尾场中被加速正电子的研究

为了研究在激光驱动的尾场中被加速正电子的动能,采用数值模拟方法,得到了在对称高斯脉冲和非对称高斯脉冲驱动的尾波场中被加速的正电子的能埴.结果表明,非对称高斯脉冲驱动尾场中的正电子的能量比对称高斯脉冲驱动尾场中的正电子的能最高.     

非对称激光等离子体尾场中被加速电子的模拟

为了研究在激光驱动的等离子体尾场中被加速电子的动力学,采用数值模拟方法得到了非对称脉冲驱动的尾波场中被加速的电子的运动相图、密度分布及势能。结果表明,非对称激光脉冲驱动尾场中电子得到很高的能量。在非对称激光脉冲驱动的激光尾场中,为了有效地加速电子,要选择恰当的上升激光脉冲长度和下降激光脉冲长度。     

激光尾场中被加速电子的动能研究

为了研究在激光驱动的尾场中被加速电子的动能,采用粒子模拟方法,得到了决定电子最大动能的尾场势的最大值和最小值,讨论了等离子体尾波静电势的最大值和最小值及其与激光脉冲长度和强度之间的关系。结果表明,捕获电子最大能量与脉冲激光强度成正比,激光脉冲长度是激光波长的10倍时电子获得的能量最大。     

Compton散射下正弦三角等离子体中正电子的加速

应用多光子非线性Compton散射模型和数值模拟方法,研究了正弦三角超强激光等离子的尾场对正电子加速,提出了将入射超强激光和非线性Compton散射光作为等离子体尾场对正电子加速的新机制,给出了正电子加速能量修正公式和数值模拟结果。结果表明:使用非对称正弦三角激光脉冲的等离子体尾场加速正电子优于对称正弦三角激光脉冲的尾场情况,散射使非对称正弦三角耦合激光脉冲宽度和上升长度与下降长度之比缩小,正电子获得的加速能量显著增大。这是因为正电子频率增大,横向速度各向异性分布增强,尾场限制了正电子横向加速能量,导致正电子在激光传输方向加速能量增大。     

超强短脉冲激光作用下尾波场对激光频率的影响研究

在非线性一维“准静态”冷等离子体模型下,推出了尾波场对激光进行频率和波数变换的理论计算公式,分析了尾波场对频率变换的影响机制,讨论了各种参量的影响程度,结果显示:(1)只要有等离子体尾波场存在,等离子体中的激光频率和波数必然要减少,其最大减幅所处的位置比尾波场幅值的位置约为靠后,且与激光强度有关;(2 )激光强度越强,激光频率和波数减少量越大,但不成线性变化关系。     

超短高功率脉冲激光与物质相互作用及其应用

超短高功率脉冲激光系统的小型化实用化极大地促进了激光与物质相互作用的物理和应用研究。回顾加拿大魁北克大学国立科学研究院材料研究所（简称ＩＮＲＳ）的超短高功率脉冲激光产生高温高密度等离子体的最新研究成果及其在分子物理和辐射约束高温高密度等离子体物理中的应用。     

超短脉冲强激光场高次谐波的历史回顾与展望

总结了近几年来超短脉冲强激光场高次谐波实验及理论方面的工作，讨论了高次谐波的重要意义及可能应用，展望了强场谐波理论及实验方面进展及可行性方案。     

强激光超短脉冲对电子直接加速

论证了激光加速带电粒子的新机制。与锐聚焦配合使用强激光超短脉冲时,加速度由光压力和具有同一方向的电场纵向分量决定。表明,(现时的)一定参数的激光可将电子加速到ε-1GeV,可与“巨大”加速器达到的能量相比。在这种情况下(与文献讨论方案不同),加速对场的初始相位不敏感,可加速低速电子,并解决加速电子由场内引出的问题。     

Simulation of the generation of ultrafast midinfrared laser pulses

A numerical simulation of an ultrafast semiconductor switch for 10.6 μm CO₂ radiation is presented. It is based on the solution of the Helmholtz electromagnetic wave equation for p-polarized light and the ambipolar diffusion equation. Calculations are performed in various time dependent inhomogeneous plasma profiles. The analysis shows that the temporal reflectivity depends on the initial visible radiation fluence, duration, and diffusion coefficient of the sample. The results support the feasibility of generating midinfrared ultrashort pulses between 100 fs and 65 ps. By proper choice of the laser fluence and the semiconductor material, longer pulses are also possible     

Stability and compression of pulses in the soliton laser

We present a theory of the soliton laser which examines how an external optical fiber enables a laser to produce shorter pulses than it could produce alone. We begin by discussing a phenomenological laser model which shows how the lower limit to the mode-locked pulse width can arise. This model is coupled to an external optical fiber cavity, into which a part of the output beam is launched. The returning pulse from the fiber cavity is then mixed with a circulating pulse in the laser at the output mirror. We have found stable solutions which are nearly periodic in the external cavity. We also find more than one solution for a given set of model parameters, depending on the initial conditions. The radiation (non-soliton) part of the propagation in the optical fiber cannot be ignored. It acts as a buffer between the tendency of the fiber to produce solitons, and the fact that a pure soliton is not an exact fixed point of the laser model.     

脉冲激光微能量测量

叙述了用热释电晶体测量脉冲激光能量原理,研制了热释电激光微能量探测器。采用放大、同步触发门控电路、峰值保持器和数字显示等技术,抑制了电磁场和其它干扰,使探测器灵敏度较高,最小可探测70毫微焦耳脉冲激光能量。     

Intracavity shaping of mode-locked laser pulses

A laser synthesizer of optical pulses is proposed. It is based on injection locking of numerous weakly coupled laser oscillators with a common resonator. A proper shaping of the susceptibility through shaping the pump beam reduces the dispersion of all orders due to the resonance transition and leads to generation of pulses close to the inverse bandwidth of the gain medium. A simple intracavity shaping mechanism allows synthesis of higher-order time supermodes directly from the laser. This technique could be applied to both active and passive mode-locked lasers with homogeneously and inhomogeneously broadened transitions. The possibility of using a compound gain medium is also discussed     

Efficient compression of high-energy laser pulses

Limitations caused by stimulated Raman scattering (SRS) for laser pulse compression in traditional fiber-grating compressors are discussed. It is shown that the scheme utilizing fibers of length L exceeding the length of the dispersion walk off L_{walk off} of pump pulses and SRS permits one to obtain high-contrast compressed pulses, their energy being no more than a few nJ, and the ultimate width being proportional to the square root of the initial pulse width. For the compression utilizing fibers of length L<L_{walk off}, the pulse energies are not limited, but the compression factor is limited to the value of 32, and the compressed pulses have a low-intensity wide pedestal. A theoretical model of high-energy pulse compression with simultaneous pedestal suppression by the polarization technique using nonlinear birefringence of the fiber is discussed. This technique is compared to the spectral windowing technique     

飞秒激光脉冲在大气中的色散及补偿

卫星飞秒激光测距理论上可达到亚微米量级的测距精度,但飞秒激光脉冲在大气中传输时由色散导致的脉冲展宽显著,会使测距精度下降。为补偿飞秒激光脉冲在大气中的色散需对其色散量进行定量计算。推导了飞秒激光脉冲在大气中的群速度色散和脉冲展宽公式,表明脉冲展宽程度和群速度色散及传输距离有关;中心波长相同的飞秒激光脉冲脉宽越窄色散越严重,而当脉宽相同时,中心波长越短色散越严重。计算比较了大气和BK7玻璃的群延时、群速度色散和三阶色散。卫星激光测距系统应采用中心波长较长的1 550 nm的飞秒激光脉冲,脉宽应适当选取。由于飞秒激光色散严重,提出了采用单模光纤序列进行粗补偿和采用光栅对进行精密补偿的两种补偿相结合的方式对其色散进行补偿。