Influence of circular aperture on high-order harmonic generation

The influence of circular aperture on the intensity of high-order harmonic generation (HHG) with intense femtosecond laser pulse was studied both experimentally and theoretically. The intensity variety of HHG with the diameter of circular aperture was observed in pulsed Ar gas. The result was discussed and interpreted in terms of the theory of Hankel transform. It is found that using the Gaussian beam truncated by an aperture could enhance the conversion efficiency of HHG at certain conditions.     

Transient saturation absorption spectroscopy excited near the band gap at high excitation carrier density in GaAs

Transient saturation absorption spectroscopy in GaAs thin films was investigated using femtosecond pump and supercontinuum probe technique at excitation densities higher than 1×10^{19}cm^{-3}. The Coulomb enhancement factor of the electron－hole plasma results in a spectrum hole at the pump wavelength. Two distinct transmission peaks at two sides of the pump wavelength are observed, arising from the bleaching of transitions from the heavy- and light-hole bands to the conduction band. The dynamic process of the transient saturation absorption is fitted using a bi-exponential function. The fast decay process is dominated by the carrier-phonon scattering and the slow process may be attributed to the electron－hole recombination.     

Quantum communication for satellite-to-ground networks with partially entangled states

To realize practical wide-area quantum communication,a satellite-to-ground network with partially entangled states is developed in this paper.For efficiency and security reasons,the existing method of quantum communication in distributed wireless quantum networks with partially entangled states cannot be applied directly to the proposed quantum network.Based on this point,an efficient and secure quantum communication scheme with partially entangled states is presented.In our scheme,the source node performs teleportation only after an end-to-end entangled state has been established by entanglement swapping with partially entangled states.Thus,the security of quantum communication is guaranteed.The destination node recovers the transmitted quantum bit with the help of an auxiliary quantum bit and specially defined unitary matrices.Detailed calculations and simulation analyses show that the probability of successfully transferring a quantum bit in the presented scheme is high.In addition,the auxiliary quantum bit provides a heralded mechanism for successful communication.Based on the critical components that are presented in this article an efficient,secure,and practical wide-area quantum communication can be achieved.     

介质的非均匀性对高次谐波影响的研究

讨论了气体介质的非均匀性对飞秒激光高次谐波产生过程的可能影响.计算结果表明,采用喷阀技术所提供的气体介质的密度梯度和气体原子运动速度的影响很小,不会产生实验上可观测的效果.这一结果支持了喷气靶在高次谐波产生中的广泛应用 关键词： 高次谐波 气体介质 各向异性 飞秒激光     

Investigation on ultrafast thrid—order optical nonlinearity of metal（dmit）2／mnt）2 Charge transfer complexes

We have investigated the transient third-order optical nonlinearity of the solutions of Metal(dmit)2/(mnt)2 salts in acetone by employing femtosecond optical Kerr gate measurement at 830nm wavelength.An order of enhancement on the second-order hyperppolarizability is found for the above salts with central atoms of Cu and Ni.We have suggested an explanation for the enhancement based on the extension of electronic conjugation by the entring Cu or Ni atom.     

Relaxation of Dense Electron Plasma Induced by Femtosecond Laser in Dielectric Materials

Electron plasma induced by a focused femtosecond pulse （130 fs, 800 nm） in dielectric materials （Soda Lime glass, K9 glass, and SiO2 crystal） is investigated by pump-probe shadow imaging technology. The relaxation of the electron plasma in the conduction band is discussed. In SiO2 crystals, a fast self-trapping process with a trapping time of 150fs is observed, which is similar to that in fused silica. However, in Soda Lime glass and K9 glass, no self-trapping occurs, and two decay processes are found： one is the energy relaxation process of conduction electrons within several picoseconds, another is an electron-hole recombination process with a timescale of lOOps. The electron collision time T in the conduction band is also measured to be in the order of 1 fs in all of these materials.     

光学发展与社会进步

人从降生开始,光就伴随其一生。宇宙的发展也跟光的发展紧密联系在一起。光学的发展过程是人类认识客观世界进程中的一个重要组成部分,是不断揭露矛盾和解决矛盾,逐渐从不确切认知走向确切认知的过程。光学确实是无处不在的,太阳能的利用,蓝光的发光,激光的焊接和切割,电影的放映,光纤通信,光合作用,X光的应用和显微镜的应用等等。光学仪器已在人们日常生活中起着无可替代的作用。列举一个最熟悉的例子,我们每天都在使用的手机就使用了三十多项光学的技术：光学玻璃、激光切割光滑的玻璃表面、激光打标、OLED和液晶显示、挡光版、背光照明、实现彩色的偏振片和滤光片、增加清晰度的增透膜、照相的镜头、成像的CCD、芯片的制造、光刻技术的应用、通过光纤进行信息的传输、蓝牙无线红外通信、光纤传感和投影等。今天,我们将从光的过去、现在和未来几个方面来探讨光对我们的生活所起到的至关重要的影响。     

双光束相干控制产生多次谐波的实验验证

利用两束相干度可改变的飞秒脉冲光对产生的五次谐波的强度特性进行了研究，发现谐波信号的强度随相干程度的增大而增加，谐波信号的最大值相对于相干零点(双光束相干度最大处)是非对称的，从而证明了合成的激光脉冲波形变化对谐波信号的影响.同时对谐波的受激放大理论进行了初步的实验探索和展望. 关键词： 五次谐波 波形变化 相干 受激放大     

失活催化剂中金属杂质测定方法研究

针对失活催化剂中残余的积炭、硫对金属杂质含量测定的影响,建立了一种以硝酸-高氯酸体系氧化溶解样品,ICP-AES准确测定失活加氢催化剂中沉积在催化剂表面的金属杂质Fe、Na、Ca、Mg含量的方法.测定结果表明,该方法的精密度小于5%,回收率在95%-113%之间,与其他方法相比,本方法准确、可靠,可用于实际分析.     

飞秒激光在三维微细体系中的应用

飞秒激光的超快特性使其能以极低的脉冲能量获得超强光场,并且激光加照区淀积的能量能以通过热扩散途径逸出辐照区域,其与透明物质相互作用是通过双光子或多光子吸收过程实现,故作用区限域于焦点核心很小体积内,因而在三维微制备及生物医学领域有着独到优势。文章介绍了飞秒激光应用于微爆炸、高密度三维光学数据存储、直写光波导及三维光子晶体制备、生物医学工程等方面的最新进展。飞秒激光三维微制备技术在微电子、计算机、光通信、生物医学等高技术领域有着广阔的应用前景。