Laser action from 1,3,5,7-tetramethyl-2,6-diethyl-8-n-propyl pyrromethene-BF2

We measured spectroscopic and laser action properties of a novel 8-position substituted pyrromethene-BF2, namely 1,3,5,7-tetramethyl-2,6-diethyl-8-n-propyl pyrromethene-BF2 complex. The laser action was performed with the corresponding dye solution in ethanol, which was placed in a Littman-type laser cavity pumped by the second harmonic of a Q-switched Nd:YAG laser. The spectroscopic measurements clearly indicated that the corresponding dye solution in ethanol exhibited intense absorption in the visible spectral region with large fluorescence quantum yield. It possesses rather low triplet-triplet absorption in the spectral region 460-550 nm and almost negligible triplet-triplet absorption in the lasing spectral region. As a consequence, it lases nearly as efficiently as commercially available benchmark laser dyes such as Rhodamine-6G and outperformed them in wavelength tunability in our laser cavity and pump geometry. (C) 2002 Optical Society of America.

Attosecond pulse extreme-ultraviolet photoionization in a two-color laser field

Attosecond-pulse extreme-ultraviolet (XUV) photoionization in a two-color laser field is investigated. Attosecond pulse trains with different numbers of pulses are examined, and their strong dependence on photoelectronic spectra is found. Single-color driving-laser-field-assisted attosecond XUV photoionization cannot determine the number of attosecond pulses from the photoelectronic energy spectrum that are detected orthogonally to the beam direction and the electric field vector of the linearly polarized laser field. A two-color-field-assisted XUV photoionization scheme is proposed for directly determining the number of attosecond pulses from a spectrum detected orthogonally. (C) 2005 Optical Society of America.

Optimization of single attosecond x-ray pulses by genetic algorithm control of the chirp and initial phase of 5 fs laser pulses

We show that the peak intensity of single attosecond x-ray pulses is enhanced by 1 or 2 orders of magnitude, the pulse duration is greatly compressed, and the optimal propagation distance is shortened by genetic algorithm optimization of the chirp and initial phase of 5 fs laser pulses. However, as the laser intensity increases, more efficient nonadiabatic self-phase matching can lead to a dramatically enhanced harmonic yield, and the efficiency of optimization decreases in the enhancement and compression of the generated attosecond pulses. (c) 2006 Optical Society of America.

Optimization of high-order harmonic by genetic algorithm for the chirp and phase of few-cycle pulses

The brightness of a particular harmonic order is optimized for the chirp and initial phase of the laser pulse by genetic algorithm. The influences of the chirp and initial phase of the excitation pulse on the harmonic spectra are discussed in terms of the semi-classical model including the propagation effects. The results indicate that the harmonic intensity and cutoff have strong dependence on the chirp of the laser pulse, but slightly on its initial phase. The high-order harmonics can be enhanced by the optimal laser pulse and its cutoff can be tuned by optimization of the chirp and initial phase of the laser pulse.

Optimal feedback control of two-photon fluorescence based on genetic algorithm

An optimal feedback control of two-photon fluorescence in the ethanol solution of 4-dicyanomethylene-2-methyl-6-p-dimethyl-amiiiostryryl-4H-pyran (DCM) using pulse-shaping technique based on genetic algorithm is demonstrated experimentally. The two-photon fluorescence of the DCM ethanol solution is enhanced in intensity of about 23%. The second harmonic generation frequency-resolved optical gating (SHG-FROG) trace indicates that the effective population transfer arises from the positively chirped pulse. The experimental results appear the potential applications of coherent control to the complicated molecular system.

Optimal feedback control of two-photon fluorescence in Coumarin 515 based on genetic algorithm

An optimal feedback control of two-photon fluorescence in the Coumarin 515 ethanol solution excited by shaping femtosecond laser pulses based on genetic algorithm is demonstrated experimentally. The two-photon fluorescence intensity can be enhanced by similar to 20%. Second harmonic generation frequency-resolved optical gating traces indicate that the optimal laser pulses are positive chirp, which are in favor of the effective population transfer of two-photon transitions. The dependence of the two-photon fluorescence signal on the laser pulse chirp is investigated to validate the theoretical model for the effective population transfer of two-photon transitions. The experimental results appear the potential applications in nonlinear spectroscopy and molecular physics. (c) 2005 Elsevier B.V. All rights reserved.

含AlF3和ZrF4氟化物玻璃的分相与析晶

以摩尔组成为8．7MgF2-17．4CaF2-8．7SrF2-13．3BaF2-13．0YF3-31．6．AlF3-7．3ZrF4的氟化物玻璃为对象，研究了玻璃的分相和析晶．研究表明，玻璃中同时含有AlF3和ZrF4时，玻璃产生明显的分相，玻璃在高温下对水比较敏感，容易产生表面析晶．玻璃内部的析晶主要来自稳定性较差的富Al相，受空气中水分的影响，玻璃表面的析晶首先产生于富Zr相．依据玻璃的分相和析晶表现，讨论了含AlF3和ZrF4氟化物玻璃的表面析晶机理．

飞行光学聚焦特性控制仪的研制

研究了长距离飞行光学（flying optics）高斯光束聚焦特性，理论研究表明：将某一特定谐振腔的瑞利长度ZR取代q参量虚部的光斑尺寸w时，q参量的ABCD定律可以从基模推广到高阶模或几个模的叠加，并推导出飞行光学实际焦距与几何焦距之差Δf的计算公式。为了精确控制飞行光学聚焦特性，研制了一套自适应飞行光学聚焦特性控制仪，实验和理论比较吻合。

Study of thin-film SO2 gas sensors by photometric and ellipsometric methods

Pt-, Pd-, and Zr-doped SnO2 thin films and dopant-free VOx films were fabricated by planar magnetron sputtering. Tests for sensitivity to SO2 for all samples were conducted at 180 degreesC, and the sensitivities were investigated ex situ with photometric and ellipsometric methods at room temperature. It was found that the optical sensitivities as well as the sensitive wavelength region for SnO2 films could be tuned by doping. The Pd-doped SnO2 films had good sensitivity in the visible range, and the Zr-doped in the near IR. The dominant sensitive wavelength region for VOx films fell into the visible range, and the ratio of the sensitivity in the visible to that in the near IR increased with O-2/Ar in the depositing atmosphere. (C) 2001 society of Photo-Optical instrumentation Engineers .

HfO2 膜料中的杂质对薄膜损伤及性能的影响

By analysis of impurity elements in HfO2 coating material, the influence of main impurity elements on the characteristic of coatings were studied. The results indicate that the metal elements and absorptive dielectric elements damage the HfO2 coatings. The more the Zr element content is, the more the absorption is for the coatings in ultraviolet wave. The negative ion element will become the gas source center and form an ejection in the process of evaporation of coating material, so decrease the damage threshold of the coatings.

HfO2的纯度对紫外多层膜反射率的影响

用辉光放电质谱法和二次离子质谱仪测定了两种HfO2材料及它们相应的单层膜中的杂质含量，结果发现，无论是在体材料中还是在用电子束蒸发技术沉积的材料单层薄膜中，ZrO2都是这两种HfO2材料中最主要的杂质。而且，这两种HfO2材料中Zr含量的差别远远大于Ti、Fe含量的差别，这说明Zr含量的差别正是引起两种HfO2膜层光学性能差别的原因。用这两种不同纯度的HfO2材料与同一纯度的SiO2材料组合，沉积形成266nm的紫外反射镜，实验结果表明这两种反射镜的反射率分别在99.85% 和 99.15%左右。这个结果与依据单层膜得出的光学常数所设计的结果符合的很好。

Influence of ZrO2 in HfO2 on reflectance of HfO2/SiO2 multilayer at 248 nm prepared by electron-beam evaporation

Influence of ZrO2 in HfO2 on the reflectance of HfO2/SiO2 multilayer at 248 nm was investigated. Two kinds of HfO2 with different ZrO2 content were chosen as high refractive index material and the same kind of SiO2 as low refractive index material to prepare the mirrors by electron-beam evaporation. The impurities in two kinds of HfO2 starting coating materials and in their corresponding single layer thin films were determined through glow discharge mass spectrum (GDMS) technology and secondary ion mass spectrometry (SIMS) equipment, respectively. It showed that between the two kinds of HfO2, either the bulk materials or their corresponding films, the difference of ZrO2 was much larger than that of the other impurities such as Ti and Fe. It is the Zr element that affects the property of thin films. Both in theoretical and in experimental, the mirror prepared with the HfO2 starting material containing more Zr content has a lower reflectance. Because the extinction coefficient of zirconia is relatively high in UV region, it can be treated as one kind of absorbing defects to influence the optical property of the mirrors. (C) 2008 Elsevier B.V. All rights reserved.