DEFORMATION ANALYSIS OF LASER SPECTRA BASEDON S_R DECOMPOSITION THEOREM

In the Fourier spectral analyzer, the Fourier spectra or the Fraunhofer diffraction pattern of an image is formed on the back focal plane when a laser beam is directed on the image lying on the front focal plane. If the image is deformed, its Forier spectra are also subjected to change. Therefore the change of the Fourier spectra provides a particular beautiful insight into the deformation of that image. Through proposing the corresponding relationship between the image and its spectra, and analyzing the change of Fourier spectra, the deformation of the image can be obtained. Based on Fourier optical theory and S-R decomposition theorem of finite deformation, in this paper, a state of the art deformation measurement technique is presented by using laser spectral analysis. The theoretical foundation of this new technique related to mathematics and optics, experimental principle and the technique of automatic recognizing and processing of rile deformed spectral image is discussed. The paper is as a special commemoration and memorial to the death anniversary of Professor Chen Zhida (1927 similar to 1998) , who initially proposed the above academic idea in early 80s.

Quantum Chemistry Study on Structures of Cluster Ions Nb_(n)S_(m)^(±)Generated by Laser Mass Spectra

ccording to the chemical bond theory we designed geometric structures ofcluster ions Nb_nS generated by laser ablation and calculated their electronic struc-tures using DV-X_a method of quantum chemistry. The results show that with theincrease of the cluster size the structures of the cluster ions change from a single-chain to a double-chain, then to a planar-net, and linking up to a net at Nb_3. Thenegative cluster ions tend to form a divergent configuration due to the extra chargeson it.

IR Spectra Analysis of SiO_2-TiO_2-GeO_2 Gel Glass of CO_2 Laser Transmitting Hollow Waveguide

Both titanium and germanium were introduced into silicon dioxide system by sol-gel method to move its region of anomalous dispersion caused by IR resonance absorption towards the wavelength of CO 2 laser.It is indicated by IR absorption spectra that as the content of SiO 2 decreases in this glass system TiO 2 and GeO 2 tends to exist in their own phases.As for the gel glass with a composition of 40SiO 2·30TiO 2·30GeO 2,when the temperature is below 600℃,germanium atoms exist mainly in Ge-O-Ge bonds.With the temperature increasing from 800℃ to 1000℃, titanium atoms in Si-O-Ti bonds almost transform into Ti-O-Ti bonds.Furthermore,a large number of Si-O-Ti and Si-O-Ge bonds formed when the temperature approaches 800℃,which makes a notable IR absorption band round the wavelength of CO 2 laser.Therefore, sol-gel based SiO 2-TiO 2-GeO 2 gel glass is a candidate material for CO 2 laser hollow waveguide.

Effect of Laser Annealing on Permeability Spectra in Co-based Amorphous Ribbon

We investigated the variation of permeability spectra and relaxation frequency in Co-based amorphous ribbon annealed by pulsed Nd:YAG laser at various annealing energy Ea. The complex permeability spectra varies sensitively with the annealing energy, where the spectra could be decomposed into two contributions from domain wall motion,μdw(f) and rotational magnetization μrot(f) by analyzing the measured spectra as a function of driving ac field amplitude. The magnitude of μdw(f) and μrot(f) in dc limit shows maximum at Ea = 176 mJ. The maximum relaxation frequency for rotational magnetization, determined by μ'(f) curve, is about 700 kHz at Ea=62 mJ but that for wall motion is about 26 kHz at 230 mJ. These variations reflect the increase of magnetic softness and microstructural change by the annealing.

UV–visible spectral characterization and density functional theory simulation analysis on laser-induced crystallization of amorphous silicon thin films

The effect of laser energy density on the crystallization of hydrogenated intrinsic amorphous silicon （a-Si：H） thin films was studied both theoretically and experimentally. The thin films were irritated by a frequency-doubled （λ= 532 nm） Nd：YAG pulsed nanosecond laser. An effective density functional theory model was built to reveal the variation of bandgap energy influenced by thermal stress after laser irradiation. Experimental results establish correlation between the thermal stress and the shift of transverse optical peak in Raman spectroscopy and suggest that the relatively greater shift of the transverse optical （TO） peak can produce higher stress. The highest crystalline fraction （84.5%） is obtained in the optimized laser energy density （1000 mJ/cm2） with a considerable stress release. The absorption edge energy measured by the UV- visible spectra is in fairly good agreement with the bandgap energy in the density functional theory （DFT） simulation.

X-Ray and VUV Spectra from the Laser Plasma Produced with “Kanal-2” Facility

The paper presents experimental results obtained on “Kanal-2” facility. Laser radiation focusing on the surface of plane magnesium targets created the high temperature plasma, which emitted X-ray and vacuum ultraviolet (VUV) radiation. This radiation spectrum was investigated with two spectrographs: the mica crystal spectrograph (working range 8.2 ? - 9.6 ?) and the grazing incidence VUV spectrograph (working rage 30 ? - 130 ?). A set of beryllium stepwise attenuators appended the diagnostic complex and allowed us to get an approximated picture of a continuous spectrum within the range of 2.2 ? - 6.2 ?. The estimation of the plasma electron temperature Te from the ratio between the intensity of the dielectronic satellites and the resonance line gives Te ~ 180 eV. The ratio between the intensity of the resonance and intercombination lines gives the electron density of the emitting zone ne ~ 2 × 1019 cm-3. Some lines observed within the spectral range of 8.5 ? - 9.1 ? belong to none of the transitions of Mg ions. Perhaps the observed spectrum is determined by the transitions in so-called hollow ions of Mg, i.e. in the ions with unfilled inner shells. The spectra obtained with the grazing incidence spectrograph and with the minimum-directioned discrepancy iteration method of spectrum reconstruction from the attenuation curve in the beryllium stepwise attenuators are also presented.

Raman Spectra of Laser Crystals NAB and NYAB and the Ligand Vibrations of Their Active Ions

The lattice vibration mode of the laser crystals NAB and NYAB are measured by Raman spectra method and the possible effects of the BO3 and NdO6 vibration modes on the non-radiative transition of the active ions are discussed.

MEBO治疗Spectra双脉冲激光祛斑术后创面的临床疗效

目的观察Spectra双脉冲激光祛斑术后创面应用湿润烧伤膏（Moist Exposed Burn Ointment,MEBO）治疗的临床效果。方法将200例采用Spectra双脉冲激光祛斑术祛斑的患者随机分为治疗组和对照组,每组100例。治疗组治疗结束后用冰袋敷面0.5~1.0 h,然后将MEBO均匀涂抹于创面,厚约1mm,每6 h换药1次,3 d后停用,并每日以冷水洁面;对照组治疗结束后仅用冰袋冰敷0.5~1.0 h,不做其他处理,保持创面清洁干燥,3 d后每日以冷水洁面,对比观察两组患者的疼痛情况、创面愈合时间。结果治疗组的疼痛情况（无痛81例,疼痛19例）与对照组（无痛25例,疼痛75例）相比,P〈0.01,差异具有统计学意义;治疗组的创面平均愈合时间（9.53 d）与对照组（10.65 d）相比,P〈0.01,差异具有统计学意义。结论湿润烧伤膏（MEBO）治疗Spectra双脉冲激光祛斑术后创面,疗效显著,具有止痛效果好、创面愈合时间短等作用。

Spectra双脉冲激光对黄褐斑抗氧化功能、甲皱微循环的影响

目的:探讨Spectra双脉冲激光祛斑术对黄褐斑患者抗氧化功能、甲皱微循环的影响。方法:105例黄褐斑患者采用随机数字表法分为观察组(n=53)和对照组(n=52),对照组接受常规治疗,观察组在常规治疗的基础上接受Spectra双脉冲激光祛斑术治疗。比较两组疗效,治疗后血清氧化应激指标、甲皱微循环积分、生活质量改善情况及患者美观满意度。结果:观察组总有效率为92.45%,显著高于对照组的76.92%(P<0.05);治疗后,两组超氧化物歧化酶(Super oxide dismutase,SOD)水平明显升高,而丙二醛(Malondialdehyde,MDA)、一氧化氮(Nitric oxide,NO)水平、甲皱微循环积分(血流速度、管袢形态、袢周状态及总积分)、黄褐斑生活质量评分(Melasma quality of life scale,MelasQOL)及皮肤病生活质量指数(Dermatology life quality index,DLQI)明显降低(P<0.05),且观察组SOD水平显著高于对照组,MDA、NO水平、甲皱微循环积分、MelasQOL评分、DLQI指数均显著低于对照组(P<0.05);观察组美观满意度为90.57%,优于对照组的71.15%(P<0.05)。结论:采用Spectra双脉冲激光祛斑术治疗黄褐斑,能通过调节患者SOD、MDA、NO水平,增强其抗氧化功能,促进甲皱微循环改善,继而提高治疗效果,改善患者生活质量,有较高的临床应用价值。

Crystal growth, spectroscopic characteristics, and Judd–Ofelt analysis of Dy:Lu_2O_3 for yellow laser

Dy：Lu2O3 was grown by the float-zone （Fz） method. According to the absorption spectrum, the Judd-Ofelt （JO） parameters Ω2, Ω4, and Ω6 were calculated to be 4.86 × 10-20 cm2, 2.02 × 10-20 cm2, and 1.76 ×10-20 cm2, respectively. The emission cross-section at 574 nm corresponding to the 4F9/2 →6H13/2 transition was calculated to be 0.53 ×10 20 cm2. The yellow （4F9/2 →6H13/2 transition） to blue （4F9/2 →6H15/2 transition） intensity ratio ranges up to 12.9. The fluorescence lifetime of the 4F9/2 energy level was measured to be 112.1 μs. These results reveal that Dy：Lu2O3 is a promising material for use in yellow lasers.

Improvement of laser damage thresholds of fused silica by ultrasonic-assisted hydrofluoric acid etching

Polished fused silica samples were etched for different durations by using hydrofluoric（HF） acid solution with HF concentrations in an ultrasonic field. Surface and subsurface polishing residues and molecular structure parameters before and after the etching process were characterized by using a fluorescence microscope and infrared（IR） spectrometer, respectively. The laser induced damage thresholds（LIDTs） of the samples were measured by using pulsed nanosecond laser with wavelength of 355 nm. The results showed that surface and subsurface polishing residues can be effectively reduced by the acid etching process, and the LIDTs of fused silica are significantly improved. The etching effects increased with the increase of the HF concentration from 5 wt.% to 40 wt.%. The amount of polishing residues decreased with the increase of the etching duration and then kept stable. Simultaneously, with the increase of the etching time, the mechanical strength and molecular structure were improved.

Self-assembled germanium nano-structures by laser-assisted oxidation

The investigation on the oxidation behaviour of Si1-xGex alloys （x=0.05, 0.15, and 0.25） is carried out. It is found for the first time that on the oxide film a germanium nano-cap with a thickness of 1.8-2.8nm and a few Ge nanoparticles with diameters ranging from 5.5 nm to 10 nm are formed by the low-temperatu.re laser-assisted dry oxidation of Si1-xGex substrate. A new scanning method on the decline cross-section of the multiple-layer sample is adopted to measure the layer thickness and the composition. Some new peaks in photoluminescence （PL） spectra are discovered, which could be related to the nano-cap and the nano-particles of germanium. A suitable model and several new calculating formulae with the unrestricted Hartree-Fock-Roothaan （UHFR） method and quantum confinement analysis are proposed to interpret the PL spectra and the nano-structure mechanism in the oxide.

Crystal growth and spectral properties of Tb：Lu2O3

The crystal growth,x-ray diffraction pattern,absorption spectrum,emission spectrum,and fluorescence lifetime of a Tb：Lu2O3 single crystal were studied.Excited at 483 nm,the peak absorption cross-section was calculated to be 3.5×10（-22）cm2,and the full width at half maximum was found to be 2.85 nm.The Judd-Ofelt（J-O）intensity parameters 2,4,and 6 were computed to be 3.79×10（-20）cm2,1.30×10（-20）cm2,and 1.08×10（-20）cm2,with a spectroscopic quality factor 4/6 being 1.20.The emission cross-sections of green emission around 543 nm and yellow emission around 584 nm were calculated to be 9.43×10（-22）cm2 and 1.32×10（-22）cm2,respectively.The fluorescence lifetimeτexp of -5D4 was fitted to be 1.13 ms.The data suggest that the Tb：Lu2O3 crystal could be a potential candidate for green and yellow laser operation.

Photoionization of NaK molecule with a double-well potential in femtosecond pump-probe pulse laser fields

The method of time-dependent quantum wave packet dynamics is used to calculate the femtosecond pump-probe photoelectron spectra and study the wave packet dynamic processes of the double-minimum potential state 6^1∑^＋ of NaK in intense laser fields. The evolutions of the wave packet and the photoelectron energy spectra with time and internuclear distance are described in detail. The wave packet dynamic information of the 6^1∑^＋ state can be extracted from the photoelectron energy spectra.

The dissociation pathways of N_2^+ in intense femtosecond laser fields

Using a neutral N2 beam as target, this paper studies the dissociation of N2^＋ in intense femtosecond laser fields （45 fs, ～ 1 × 10^16 W/cm^2） at the laser wavelength of 800 nm based on the time-of-flight mass spectra of N＋ fragment ions. The angular distributions of N^＋ and the laser power dependence of N^＋ yielded from different dissociation pathways show that the dissociation mechanisms mainly proceed through the couplings between the metastable states （A, B and C） and the upper excited states of N^＋.A coupling model of light-dressed potential energy curves of N2^＋ is used to interpret the kinetic energy release of N^＋.

Dependence of Laser Ablation Produced Gold Nanoparticles Characteristics on the Fluence of Laser Pulse

Effect of laser fluence on the characteristics of gold nanoparticles (NPs) produced by laser ablation method is investigated experimentally. Five samples of gold NPs were synthesized by nanosecond pulsed laser ablation of a high purity gold plate in distilled water at five different fluences in the range of 1-3 J/cm2. Results show that in this experimental condition gold NPs are produced by nucleation of Au atoms in the plasma, generated on the target surface during the ablation process. There is threshold fluence at which absorption of laser energy by water rises significantly. Absorption of the laser energy by water leads to increase oxygen atoms in the ablation medium and formation of gold oxide NPs. By increasing the laser fluence below the threshold, size of produced NPs decreases while by increasing the laser fluence above the threshold size of produced NPs increases.

The Transient Time-Resolved Absorption Spectra of 1-Naphthylacetic Acid

The transient absorption spectra of 1-naphthylacetic acid in tetrahydrofuran have been obtained by laser flash photolysis technique. The transient species bands are at 509, 535 and 553 nm. These peak intensities increase in the maximum values at 10.4 mu s.

Effect of Laser Fluence on the Characteristics of Ag Nanoparticles Produced by Laser Ablation

6-12 nm silver nanoparticles were synthesized by the pulsed laser ablation of a high purity silver bulk in distilled water. Effect of laser fluence on the size, morphology and structure of produced nanoparticles has been studied experimentally. Pulses of a Q-switched Nd:YAG laser of 1064 wavelength at 7 ns pulse width at different fluences were employed to irradiate the silver target in water. The UV-Visible absorption spectra of the Ag nanoparticles exhibit surface plasmon resonance absorption peak in the UV region. TEM and SEM micrographs, in a good agreement with DLS results, indicate that with increasing the laser fluence the average size of spherical Ag nanoparticles is decreased. It is found that Ag nanoparticles exhibit photoluminescence emission with two peaks because of the inter band transition and electron-hole recombination.

Plasma properties of laser-ablated St target in air

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THz wave emission from argon in two-color laser field

Terahertz （THz） wave emission from argon atom in a two-color laser pulses is studied numerically by solving the one-dimensional （1D） time-dependent Schr6dinger equation. The THz spectra we obtained include both discontinuous and continuum ones. By using the special basis functions that we previously proposed, our analysis points out that the discontinuous and continuum parts are contributed by bound-bound and continuum-continuum transition of atomic energy levels. Although the atomic wave function is strongly dressed during the interaction with laser fields, our identification for the discontinuous part of the THz wave shows that the transition between highly excited bound states can still be well described by the field-free basis function in the tunneling ionization regime.