Combinatorial discovery of anomalous substrate effect on the photochemical properties of transition metal-doped epitaxial SrTiO3 heterostructures

Epitaxial Sr(V_xCr_yTi_1−x−y)O₃ (0≤x+y≤0.05) ternary composition spreads were grown on two different single crystal substrates, LaAlO₃ and Nb-doped SrTiO₃, by use of combinatorial laser molecular beam epitaxy with a specially patterned slide masking plate. The photocatalytic activity on the composition spreads was evaluated by the photo-reduction of Ag⁺ in an AgNO₃ aqueous solution to deposit Ag metal on the spreads. The V-doping effect was found to depend greatly on the substrate: the photodeposition of Ag was much enhanced in the composition region of SrV_0.05Ti_0.95O₃ only on the Nb-doped SrTiO₃, but not on the LaAlO₃ and non-doped SrTiO₃.     

非线性放大环形镜“8”字腔光纤激光器实验研究

使用976 nm半导体激光器作为抽运源,对利用非线性放大环形镜（NALM）锁模运行的掺Yb3+光纤激光器进行了实验研究,获得了脉冲宽度43.6 ps,中心波长为1053.3 nm的锁模脉冲激光输出, 光谱宽度8 nm, 输出功率为0.2 mW, 重复频率为18.2 MHz, 经过放大, 通过光栅对腔外色散补偿,在腔外产生了宽度616 fs的脉冲激光.     

Excimer laser ablation of thin titanium oxide films on glass

Thin titanium dioxide films are deposited on glass substrates by magnetron sputter deposition. They are irradiated in air, by means of a KrF excimer laser. The ablation rate is measured as a function of the laser fluence per pulse, F, and of the number of pulses, N. Above a fluence threshold, the films are partially ablated. The ablated thickness does not vary linearly with N. This is the signature of a negative feedback between the film thickness and the ablation rate. The origin of this negative feedback is shown to be due to either thermal or electronic effects, or both. At high F, the film detachs from the substrate.     

ZrO2薄膜的改性与抗激光损伤研究

 采用水热合成技术，制备了ZrO₂胶体，用旋涂法镀制了单层ZrO₂介质膜以及添加了有机粘合剂PVP的复合ZrO₂-PVP薄膜。采用X射线衍射(XRD)、椭偏仪、红外分光光度计（FTIR）、原子力显微镜（AFM）等仪器对干凝胶及薄膜进行了性能测试和表征，并用输出波长为1.064 μm、脉宽为10 ns的电光调Q激光系统产生的强激光测试其激光损伤阈值。测得ZrO₂和ZrO₂-PVP薄膜在300 ℃热处理60 min后的激光损伤阈值分别为24.5 J/cm²和37.8 J/cm²。研究表明：添加有机粘合剂后的复合薄膜具有平整的表面结构；有机粘合剂的添加有助于提高薄膜的折射率和激光损伤阈值，其中，ZrO₂-PVP 复合薄膜的折射率可高达1.75，激光损伤阈值达到37.8 J/cm²，比ZrO₂单层膜的激光损伤阈值提高50%。     

Laser spectroscopy and imaging of gallbladder stones, tissue and bile

Laser spectroscopic study of billary calculi and tissues is described. Fluorescence spectra of human gallbladder stones, bile and tissues were recorded with streak camera in the frequency and time domain. Potential of fluorescence as a diagnostic tool to discriminate between the intended target and the surrounding tissues and bile is evaluated. Initiation of fragmentation process is visualized by high-speed shadowgraphy, interferometry performed during the laser impact and generation of plasma causing growth and collapse of bubbles.     

Optimization of near-field optical field of multi-layer dielectric gratings for pulse compressor

Multi-layer dielectric (MLD) gratings for pulse compressors in high-energy laser systems should provide high diffraction efficiency as well as high laser induced damage thresholds (LIDT). Nonuniform optical near-field distribution is one of the important factors to limit their damage resistant capabilities. Electric field distributions in the gratings and multi-layer film region are analyzed by using Fourier modal method. Optimization of peak electric field in the gratings ridge is performed with a merit function, including both diffraction efficiency and electric field enhancement when the top layer material is HfO₂ and SiO₂, respectively. A set of optimized gratings parameters is obtained for each structure, which reduce the peak electric field within the gratings ridge to being respective 1.39 and 1.84 times the value of incident light respectively. Finally, we also discuss the effects of gratings refractive index, gratings sidewall angle and incident angle on peak electric field in the gratings ridge.     

The first target experiments on the National Ignition Facility

A first set of shock timing, laser-plasma interaction, hohlraum energetics and hydrodynamic experiments have been performed using the first 4 beams of the National Ignition Facility (NIF), in support of indirect drive Inertial Confinement Fusion (ICF) and High Energy Density Physics (HEDP). In parallel, a robust set of optical and X-ray spectrometers, interferometer, calorimeters and imagers have been activated. The experiments have been undertaken with laser powers and energies of up to 8 TW and 17 kJ in flattop and shaped 1–9 ns pulses focused with various beam smoothing options. The experiments have demonstrated excellent agreement between measured and predicted laser-target coupling in foils and hohlraums, even when extended to a longer pulse regime unattainable at previous laser facilities, validated the predicted effects of beam smoothing on intense laser beam propagation in long scale-length plasmas and begun to test 3D codes by extending the study of laser driven hydrodynamic jets to 3D geometries.     

Growth and characterization of β-SiC films obtained by fs laser ablation

We achieved the growth of cubic silicon carbide (SiC) films on (1 0 0)Si substrates by pulsed laser deposition (PLD) at moderate temperatures such as 750 °C, from a SiC target in vacuum. The as-deposited films are morphologically and structurally characterized by scanning electron microscopy (SEM), conventional and high-resolution transmission electron microscopy (TEM/HRTEM). The morphology of deposited films is dominated by columns nucleated from a thin nanostructured beta silicon carbide (β-SiC) interface layer. The combined effects of columnar growth, tilted facets of the emerging columns and the presence of particulates on the film surface, lead to a rather rough surface of the films.     

High-bandwidth one-and two-particle microrheology in solutions of wormlike micelles

We have developed a large-bandwidth two-particle microrheology technique to measure loss and storage moduli of viscoelastic materials from 0.1 Hz to about 100 kHz using laser trapping and interferometry. We found that quantitative agreement between one- and two-particle microrheology exist in entangled solutions of wormlike micelles chosen as a simple model viscoelastic system. These results validate both experimental method and data interpretation. The consistent results also prove that in a simple system, where the solution length scales are much smaller than the micron probe size, one-particle microrheology can accurately measure bulk viscoelastic parameters.This paper was presented at the AERC 2005     

Initial Operation of Thomson Scattering Diagnostic on the HL-2A Tokamak

In this article, we describe the major instruments of laser Thomson scattering system on HL-2A, and introduce the experimental measuring results of one-point electron temperature and density in the core plasma mostly.