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Influence of exciting laser sheet intensity distribution on the fluorescence intensity distribution in a Planar Laser-induced Fluorescence(PLIF) experiment was analyzed.Based on cylindrical lens array,a laser sheet shaping system was designed.According to the requirement of PLIF,several parameters were optimized with ray tracing method.The laser beam shaping experiment system was established and applied to the PLIF experiment for dye laser beam shaping and acquiring smoothing laser sheet with the nonuniformity no more than 4%.With the uniformity laser sheet beam,PLIF was applied to the measurement of fluorescence imaging of OH in alcohol flame and CH4/air premixed combustion.

ZnO nanowire arrays with controlled diameter,density and orientation were prepared on the ZnO film coated substrates via hydrothermal method.The ZnO film were fabricated by atomic layer deposition(ALD) method and annealed at different temperatures.The annealing temperature has strong influences on the grain size,crystalline structure and defect property of the ZnO film.The diameter,density and orientation of ZnO nanowires depended on the features of the ZnO film.Field-emission scanning electron microscopy(SEM),X-ray diffraction(XRD) and photoluminescence(PL) were applied to analyze the ZnO film and ZnO nanowire arrays.The as-prepared vertical aligned ZnO nanowires are highly suitable for use in nanodevices,such as light-emitting diodes and solar cells.

A low-cost and effective method to fabricate hexagonally patterned urchin-like ZnO nanowire arrays was demonstrated.The ordered monolayer of polystyrene(PS) spheres is obtained by self-assembly,and the monolayer is used as a template to grow ZnO nanowires with complex hierarchical structures via hydrothermal method.The urchin-like ZnO nanowire arrays are composed of PS sphere and ZnO nanowires.The nanowires have uniform diameter,and the length of the nanowires can be controlled by the growth time.This method provides a promising way to fabricate ZnO one-dimensional nanostructures for applications as sensor arrays,solar cells and photocatalysis.

ZnO nanowires were assembled on Au interdigital electrodes by dielectrophoresis method and fabricated the nanowires UV detector.In order to assemble the ZnO nanowires on interdigital electrodes,the long ZnO nanowires were grown three times by hydrothermal method.Then,the ZnO nanowires was annealed under 700 ℃,which increased the availability of the surface defects.The photoresponse current ratio and recovery time of the UV detector fabricated with the annealed ZnO nanowires were significantly improved.The possible mechanism was studied by the photoluminescence and photoresponse spectra.

A molecular Filtered Rayleigh Scattering(FRS) diagnostic system was demonstrated to measure thermodynamic properties in combustion environments.The diagnostics system was composed of a narrow line width laser,a molecular/atomic absorption filter and a collection device such as ICCD.The absorption filter was used to modify the spectra of the Rayleigh scattering signal from the flow field illuminated by a laser sheet from a Nd:YAG pulsed laser.The laser was tuned to an absorption line of iodine vapor contained in the filter.This caused Mie scattering and background scattering from solid particles and strong absorption on the surface while much of Doppler broadened Rayleigh scattering was transmitted through the filter.The thermodynamic parameters were deduced from the measured transmission of the molecular Rayleigh scattering.The FRS diagnostic system and the iodine filter cell were described.On the basis of diagnosing FRS image and measuring iodine vapor absorption spectrum,the 2D temperature and density fields of methane/air premixed flame were obtained.The measured density at 15 mm above the burner surface is 0.19 kg/m3,and temperature is(1 827±84) K,which is good agreement with the results measured by using CARS method in the same condition.The uncertainty of temperature measurement by FRS is less than 8%.Furthermore,FRS technique was used to diagnose the atomization steam and supersonic exhaust flows.The results turbulence structures on the area of laser action were obtained.These demonstrate the abilities of the FRS technique to measure temperature and density fields and to enhance flow visualization in a combustion environment.

A multi-cavity passive nanosecond laser pulse stretching system was designed.The system could reduce laser peak powers and avoid the laser induced plasma spark,so that it reduces background interference and improves the signal to noise ratio in combustion diagnostics.The theoretical model of the pulse-stretching process for an arbitrary number of optical ring cavities was introduced,and several key parameters that affect on pulse width,beam-splitter reflectivity,cavity length and total number of optical cavities were analyzed.Finally,the designed multi-cavity laser pulse stretcher was used in broadening the Nd:YAG laser harmonic pulse width.Results indicate that a 7.8 ns input laser pulse has been converted into approximately the output laser pulses in 17 ns,35 ns and 72 ns,respectively.Furthermore,the laser peak power has been reduced to 9% of the original laser peak power,meanwhile,it maintains the good beam quality.The stretcher was also used in the spontaneous Raman scattering experiments,and results show it well resolves the laser induced breakdown spectroscopy of the Raman signal and achieves good results.

The gain characteristics of laser gyro were investigated by measuring the relative strength of the laser gyro′s side spectrum.It was obtained experimentally that the gain of the laser gyro increases with the increasing of the current,the gyro gain presents the saturated gain phenomena with the increasing of the total pressure and the gain reaches a maximum value when the total pressure is about equal to 4P0.By comparing the time-varying gain curves of aluminum cathode and B cathode gyroscope in the gyro′s start-up phase and corrying out error analysis of experimental data,the experimental results show that the gain stability and anti-environmental interference capability of B cathode gyro are better than that of aluminum cathode gyro.The gain of active medium and the beat′s frequency shift induced by the Langmuir flow effects both are related to the population density difference of the producing laser′s upper and lower level.The experimental results show that the zero drift′s stability of the laser gyro can be evaluated by the gyro gain′s stability.