Saturated absorption and nonlinear refraction of silicate glasses doped with silver nanoparticles at 532 nm

The nonlinear optical characteristics of silicate glasses doped with silver nanoparticles are investigated by Z-scan technique using second harmonic radiation of picosecond Nd:YAG laser (=532 nm, =55 ps). The real and imaginary parts of third-order nonlinear susceptibility of silver-contained glasses were measured. It was found that the sign of Im ⁽³⁾was negative due to saturated absorption and the sign of Re ⁽³⁾ was changed from negative (self-defocusing) to positive (self-focusing) with growth of laser radiation intensity. The mechanisms responsible for saturated absorption and nonlinear refraction are discussed.     

Branes,Quantum Nambu Brackets and the Hydrogen Atom

The Nambu-bracket quantization of the hydrogen atom is worked out as an illustration of the general method. The dynamics of topological open branes is controlled classically by Nambu brackets. Such branes then may be quantized through the consistent quantization of the underlying Nambu brackets: properly defined, the quantum Nambu-brackets comprise an associative structure, although the naive derivation property is mooted through operator entwinement. For superintegrable systems, such as the hydrogen atom, the results coincide with those furnished by Hamiltonian quantization - but the method is not limited to Hamiltonian systems.     

Homotopy of the classical configuration space for the two-magnon sector of a magnetic Heisenberg ring

A finite Heisenberg magnetic ring with an arbitrary single-node spin and two spin deviations from the ferromagnetic saturation is considered as the system of two Bethe pseudoparticles. The set of all relevant magnetic configurations spans a surface which can be recognised as a Mőbius strip. The dynamics of the system imposes the double twist of all regular orbits of the translation symmetry group.     

Interaction of electromagnetic waves with a magnetized nonuniform plasma slab

The absorption, reflection, and transmission of electromagnetic waves by a nonuniform plasma slab immersed in an ambient uniform magnetic field of various strengths are studied in this paper. The effects of the plasma parameters and magnetic field strength on the absorbed, reflected, and transmitted power are discussed. The magnetized nonuniform plasma slab is modeled by a series of magnetized uniform plasma subslabs. The calculation results show that the effects of the magnetic field strength and density gradient on the absorbed power, as well as the frequency band of resonant absorption, are significant. A complete analysis utilizing the scattering matrix method is also used to compare the above calculation results which neglect multiple reflections between subslab interfaces. Broadband absorption of electromagnetic waves can be achieved by changing the magnetic field strength and plasma density. More than 90% of the electromagnetic wave power can be absorbed in a magnetized nonuniform plasma slab with width of 12 cm and the absorption bandwidth can range from 1 to 20 GHz with different plasma parameters and external magnetic field strengths.     

Fabrication of Micro -Optical Devices by a Femtosecond Laser

Femtosecond laser is a perfect laser source for materials processing when high accuracy and small structure size are required. Due to the ultra short interaction time and the high peak power, the process is generally characterized by the absence of heat diffusion and, consequently molten layers. Various induced structures have been observed in materials after the femtosecond laser irradiation. Here, we report on fabrication of micro-optical devices by the femtosecond laser. 1) formation of optical waveguide with internal loss less than 0.5dB/cm in the wavelength region from 1.2 to 1.6 mm, by translating a silica glass perpendicular to the axis of the focused femtosecond laser beam; 2) nano-scale valence state manipulation of active ions inside transparent materials; 3) space-selective precipitation and control of metal nanoparticles inside transparent materials; The mechanisms and applications of the femtosecond laser induced phenomena were also discussed.     

Analysis of CCD moiré pattern for micro-range measurements using the wavelet transform

A new approach based on the moiré theory and wavelet transform (WT) is proposed for measuring the micro-range distance between a charge-couple-device (CCD) camera and a two-dimensional reference grating. The micro-range distance is determined by measuring the pitch of the moiré pattern image, which is digitized by a CCD camera. A one-dimensional WT algorithm is applied to estimate the pitch of the moiré pattern. Experimental results prove that this technique is very efficient and highly accurate. The moiré range finder is an economic technique for measuring a micro-range distance.     

Numerical study of the effects of the rupture process of a secondary diaphragm in expansion tubes

The results of a numerical study are described in which the interactions of a primary shock wave with a secondary diaphragm in expansion tubes are taken into account. The developing wave pattern in the interacting process of the shock with a secondary diaphragm are visualized by many kinds of figures (e.g., the time-distance diagrams of the wave phenomena on the axis, the acoustic impedance contours, and the time histories of the pitot pressure on the axis), and the influences of the shape and rupture process of the diaphragm on the quality of the test gas are explored.     

Effect of Ultrashort Pulsed Laser and X-Ray Irradiation on Au+ -Doped Glass

Au nanoparticles were precipitated inside Au+-doped glass samples after irradiation by femtosecond laser or x-ray. Femtosecond laser and X-ray irradiation result in decreasing of anneal temperature and critical size for the precipitation of Au nanoparticles.     

用于高速摄影变象管的软X射线光电阴极

光阴极由衬底(包括介质阴极的导电基底)和光电发射膜构成。采用了聚丙烯、Formvar和Paylene三种有机薄膜作阴极衬底。建立了这些薄膜的制备技术。用一台自制的软X射线单色仪在277—7469ev光子能量范围内测量了这些薄膜的透过率。 研究了CsI、CsBr、Au和MgF₂四种光电阴极的光电发射特性和光电发射与阴极厚度的关系,找出了最佳阴极厚度。用软X射线单色仪在277—7469ev光子能量范围内测量了最佳厚度阴极的绝对量子效率,四种阴极最大值分别为4.50、2.90、0.25和0.12。我们还在同一阴极衬底上分区制备了四种阴极,在变象管荧光屏上比较其亮度,结果和测量的一致。 用LAB5型表面分析仪对CsI和Au阴极的光电子初能量分布作了测量,CsI阴极光电子初能量分布半高宽远小于Au。因此CsI是适用于高速摄影变象管比较理想的软X射线光电阴极。