Thermal effects and output power characteristics of kilowatt all-fiber master-oscillator power amplifier (MOPA) are investigated. Proper designs for cooling apparatus are proposed and demonstrated experimentally, for the purpose of minimizing splice heating which is critical for the reliability of high power operation. By using these optimized methods, a thermal damage-free, highly efficient ytterbium-doped double-clad fiber MOPA operating at 1080 nm with 1.17 kW output was obtained. The maximum surface temperature at the pump light launching end splice of the booster amplifier was 345 K, and the temperature rise for this key splice was 0.052 K/W.

We prepared 3 kinds of Li + -doped BaTiO 3 ceramics by the solid-state reaction method: (i) (Ba 1Àx Li x )TiO 3Àx/2 having A-site Li + , (ii) Ba(Ti 1Àx Li x )O 3À3x/2 having B-site Li + , and (iii) x/2 Li 2 CO 3 +BaTiO 3 mixed one, for which we investigated the stable site of Li. The density of all prepared ceramics is above 95%. The results show that the lattice structure, the grain size, and the electric properties of Li + -doped BaTiO 3 ceramics are dependent on Li + site. According to the increase in Li content, the cell volume of Ba 1Àx Li x TiO 3Àx/2 decreases, but that of BaTi 1Àx Li x O 3À3x/2increases. That of x/2Li 2 CO 3 +BaTiO 3 decreases by the small addition of Li, but increases by the large addition of Li. All Li + -doped ceramics show antiferroelectriclike double hysteresis loops. The shape of loops and the dielectric properties are also dependent on the Li site. We suggest that the role of oxygen vacancy accompanied by the Li-doping is important. By comparison with the results of 3 type ceramics, it is concluded that at x/2Li 2 CO 3 +BaTiO 3 ceramics, the Li + prefers to favorably substitute Ba 2+ at A site for the low concentration of Li but its location was changed to Ti 4+ site for the high concentration of Li.

The analytical vectorial structure of HGB is investigated in the far field based on the vector plane wave spectrum and the method of stationary phase. The energy flux distributions of HGB in the far-field, which is composed of TE term and TM term, are demonstrated. The physics pictures of HGB is illustrated from the vectorial structure, which is important to understand the theoretical aspects of both scalar and vector HGB propagation.

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The effect of laser fluence on the crystallization of amorphous silicon irradiated by a frequency-doubled Nd:YAG laser is studied both theoretically and experimentally. An effective numerical model is set up to predict the melting threshold and the optimized laser fluence for the crystallization of 200-nm-thick amorphous silicon. The variation of the temperature distribution with time and the melt depth is analyzed. Besides the model, the Raman spectra of thin films treated with different fluences are measured to confirm the phase transition and to determine the optimized fluence. The calculating results accord well with those obtained from the experimental data in this research.

By using quite uniformly nine-stacks side-around arranged compact pumping system, a high power Nd:YAG ceramic quasi-CW laser with high slope efficiency of 62% has been demonstrated. With 450 W quasi-CW stacked laser diode bars pumping at 808 nm, performance of the Nd:YAG ceramic laser with different output coupling mirrors has been investigated. Optimum output power of 236 W at 1064 nm was obtained and corresponding optical-to-optical conversion efficiency was as high as 52.5%. The laser system operated quite stably and no saturation phenomena have been observed, which means higher output laser power could be obtained if injecting higher pumping power. The still-evolving Nd:YAG ceramics are potential super excellent media for high power practical laser applications.

In this paper, the Maxwell–Wagner effect and the charge characteristics of the heterogeneous interface at the action of higher electric field and elevated temperature are investigated by means of electret technology. A composite membrane with a double-layer structure of a polypropylene (PP) film and a fluorinated ethylene propylene copolymer (FEP) film was made. After being polarized under electric field and elevated temperature, the component PP and FEP films of the composite membranes were separated. The charge density of the PP and FEP films was measured to analyze the characteristics of interfacial charge in the composite membrane. Experimental results directly prove that the charge characteristics at the interface of the composite membranes are consistent with the result calculated by the Maxwell–Wagner effect. The polarity of the interfacial charge can be switched by changing the polarity of the polarizing voltage. The characteristics of the accumulated interfacial charge are strongly dependent on the conductivity, which is affected by the temperature and the polarizing electric field. A new phenomenon, that is, the measured charge density is much higher than that calculated by the Maxwell–Wagner effect, is found. The reason is ascribed to the electret effect from the FEP and PP films. This research provides a new insight into the charge characteristics at the heterogeneous interface.