Microchannel plate (MCP) is an important signal multiplier. The original reduced lead silicate glass MCP was coated with amorphous alumina by atomic layer deposition (ALD), using trimethylaluminium Al(CH3)3(TMA) and water as precursors, to enhance the electron gain characteristics. The electrical properties of ALD-MCP at different deposition temperatures, cycles and annealing processing were investigated. The results indicated that the electron gain showed a Bigaussion trended electron gain-deposition temperature behavior at the ALD deposition temperature controlled from 120°C to 300°C with 60 deposition pulse cycles of TMA/H2O, while, the bulk resistances of which were basically unchanged. Moreover, the optimum deposition cycles were increased at the maximum electron gains with the rising deposition temperature. Besides, the modified effect of ALD-MCP was significantly affected by the processing parameters, the electrical properties of which even deteriorated with the unsuitable one. The electron gain and dark current was mainly related to the concentration of hydroxyl on the surface of microchannel layer. With an excessive annealing temperature at 400°C, despite the electron gain of ALD-MCP was almost 2×104 , the dark current of which would increase dramatically, even more than four times larger than that of the original hydrogen reduced MCP.
Based on the Black-body radiation theory, a multi-wavelength photoelectric detection system for the on-line measurement of temperature and components of the detonation field is designed. In this system, the detonation spectrum is split by bifurcated optical fiber and filters, then, received by the photoelectric-detectors and convert to electrical signal. Finally, the temperature evolution process is derived through regression algorithm. Besides, concentrations of certain components can also be revealed through real-time detection of corresponding spectral lines. The spectral response coefficients and the whole system are calibrated with a standard tungsten lamp and a standard radiation source respectively. With this system, experiments are carried out, and, the variations of denotation temperature and concentrations of some key components are recorded.
In this paper, an analytic model of beam profile error evaluation for detector array method is advanced. The model based on Gaussian beam distribution considering spatial sampling frequency, the non-uniformity of detectors and the high frequency components of integral laser spot. Finally, the analytic error model of laser beam profile evaluation was obtained by derivation and calculation. The model is adapted to calculate the integral energy, the beam centroid, and beam size of Gaussian approximation beam and can be extended to monotonous distribution beam.
In this paper, we designed an optical attenuator based on optical scatting. Which consist of an optical scatting material and cylindrical attenuation structure. The diffusing characteristics of material and attenuation properties of the device have been simulated by ray-tracing, and the simulated results agree very well with the experimental results. The attenuator has been successfully used in high energy laser beam intensity profile measurement system.
Power in the Bucket (PIB) is a key index to describe the quality of Laser. Actually it is hard to precisely measure it. In this work, the numerical simulation on ideal Gauss beam and flat beam with different apertures were carried out. The results show that the problem can be overcomed by guaranteeing the transmission of the aperture. And 97% is a suggested value according to the analysis.
The multi-tone amplification for the purpose of mitigating stimulated Brillouin scattering (SBS) effect is investigated. Different wavelengths and power ratio are considered in the simulation model to achieve optimal results. The numerical simulation results indicate that SBS is effectively suppressed in a fiber amplifier with an output from 53.7W to 96.9W by utilizing this approach.
The discoloration and optical characteristics of the gold plating film under long-time high power laser irradiation are investigated. The fabrication process of gold plating on nickel underplate on rough surface of copper and aluminum alloy substrates is introduced. The measurement results of the diffuse reflectivity for the samples with different surface roughness indicate that roughness of the gold layer surface should be 4μm to obtain the maximum value of diffuse reflectivity. The discoloration and variation of diffuse reflectivity are experimentally studied under 2000W irradiation. The research results show that the discoloration and degrading of reflectivity are caused by the diffusion of Ni to the gold plating surface and forming NiO thin film due to the porosity of the gold film and high temperature treatment. A change of diffuse reflectivity related mechanism is described. Several plating solution recipes are used to eliminate the discoloration and mitigate the degrading of the reflectivity on gold surface.
In this paper, Torrance-Sparrow and Oren-Nayar model is adopt to study diffuse characteristics of laser target board. The model which based on geometric optics, assumes that rough surfaces are made up of a series of symmetric V-groove cavities with different slopes at microscopic level. The distribution of the slopes of the V-grooves are modeled as beckman distribution function, and every microfacet of the V-groove cavity is assumed to behave like a perfect mirror, which means the reflected ray follows Fresnel law at the microfacet. The masking and shadowing effects of rough surface are also taken into account through geometric attenuation factor. Monte Carlo method is used to simulate the diffuse reflectance distribution of the laser target board with different materials and processing technology, and all the calculated results are verified by experiment. It is shown that the profile of bidirectional reflectance distribution curve is lobe-shaped with the maximum lies along the mirror reflection direction. The width of the profile is narrower for a lower roughness value, and broader for a higher roughness value. The refractive index of target material will also influence the intensity and distribution of diffuse reflectance of laser target surface.