The SiO2-B2O3-La2O3-BaO glass has emerged as an important material due to its high performance. The effect of BaO content on the properties of SiO2-B2O3-La2O3-BaO glass such as density, thermal expansion coefficient, refractive index, and transmissivity were systematically studied. The results indicate that BaO content had influence on the density, refractive index and thermal expansion coefficient of the SiO2-B2O3-La2O3-BaO glass, BaO content did not have obvious impact on the transmissivity of SiO2-B2O3-La2O3-BaO glass.
High energy 1064 nm Q-switched laser output is obtained by LD vertical array end pumping Nd:YAG. For different divergence angles of fast axis and slow axis of LD array, aspheric lens are used for beam shaping of LD array. The results show that light intensity distribution of output laser is very sensitive to the structure of the shaping system, which can be controlled by adjusting the spatial position of pumping, such as the distance between the aspheric lens pair, the distance between the front end of the crystal rod and the aspheric lens, and the approximate Gaussian beam was obtained without damage. When the distance between the aspheric lens pair is 24mm, the distance between the crystal rod and aspheric lens is 4mm, a 1064 nm Q-switched laser with single pulse energy of 80.8 mJ and pulse width of 10 ns was obtained
The high gain of pumping end in end-pumped all solid state lasers can easily cause self-excited oscillation, which limits the output energy of Q-switched laser. In order to obtain a 1064 nm Q-switched laser with high energy, high conversion efficiency and compact structure, the following three aspects are mainly studied to suppress the self-excited oscillation caused by the end pump: (1) the doping concentration of active particles is optimized to reduce the end gain of laser medium, (2) the wavelength of pump light is changed by adjusting temperature of laser diode to deviate from absorption peak of Nd:YAG, (3) Nd:YAG rod is processed by tapered side, which improves the difficulty of self-excited oscillation. By using the above techniques, a 1064 nm Q-switched laser with output energy of 100 mJ is obtained at a pump current of 20 Hz and 170 A, and the corresponding dynamic to static Q-switching ratio is 77%. The three technical means proposed in this study complement each other and work together, providing a practical and effective technical way for obtaining high-energy end pumped Q-switched laser.
In this paper, the finite element model of the fiber optic plates is established by using the finite element software. The simulation process is basically in line with the actual production process of the fiber optic plates. According to the simulation results, the deformation degree and speed of each part of the fiber optic plates in the process of melting pressure, as well as the changes of stress and strain of each part in the process of forming are analyzed. The results show that the deformation speed and degree of different parts are different in the process of melting pressure of fiber optic plates, especially the upper and lower end faces and side edges of fiber optic plates; and the stress and strain of each part are constantly changing, and the stress and strain values of the upper and lower end faces and side edges of fiber optic plates are larger than others.
The microchannel-plate-based x-ray optics is a spherical crown containing millions of square microchannels, reflecting the small incident angle light at a certain angle through the inner wall of the channels. Structure defects may exist in the square microchannel array. In this paper, the effects of structure defects on the imaging performance were studied through simulation and MPO preparation experiment. The structure defects involved in the paper include two types, chamfered channels and tilting channels. The experimental results are consistent with the simulation images, proving that the simulations are correct. The results show that the imaging of MPO with standard square channels array is a symmetrical cross. The presence of chamfers in corner of the channels results in a weak secondary small cross in the 45° direction of the obvious cross. For the case that the channels are tilted slightly, the center of the cross deviates from the imaging center, and the cross becomes an asymmetric cross. This study provides a theoretical guidance for precise control of array structures in the preparation of MPO.
The optical imaging system is the the core device in the extrem ultraviolet (EUV) astronomical telescope. Because of its light weight, large field of view, high resolution, the lobster-eye optical imaging system is considered to be the best imaging system for EUV. The curved square hole microchannel plate is an imitation lobster-eye type optical imaging system. The channels of the traditional curved square hole microchannel plate are generally arranged in a square shape, and the image is a cross image, which only the cross area is effectively detected, so the detection efficiency is low. In this paper, all the square hole channels are pointed to the center by radial arrangement, thereby the detection efficiency is improved. However, this arrangement cannot achieve close alignment, and there are a large number of voids in the structure, which reduces the density of the focusing unit. In this paper, the simulation of the radial arrangement of the square hole microchannel structure is carried out by Tracepro simulation software. Through the high-precision wire drawing method, radial arrangement technology, and distortion-free control, the drawing precision of the square wire is improved, the square wire structure defects are eliminated, and the square hole microchannel plate with uniform structural height is prepared.
The resistive plate chamber (RPC) is a gaseous parallel-plate detector, the glass resistive plate is the key element of RPC. In order to meet the requirement of high flux particle detection, it is urgent to develop low resistivity electroconductive glass. For this purpose, we designed the glass of SiO2-B2O3-P2O5-Al2O3-MxOysystem, the MxOy was chosen as Fe2O3, V2O5 and MnO2. In this paper, the formation abilities and conductive properties of glass were studied by adjusting the contents of the glass forming body and MxOy. The results showed that P2O5-Al2O3and P2O5-B2O3 built a quasi-[SiO4] tetrahedron structure as the glass forming body, the SiO2strengthened the network, which greatly improved the stability of the glass. Meanwhile, the addition of B2O3 and P2O5 could enhance the doping ability of MxOy in the whole glass system, which was benefit to reduce the resistivity of glass. Three transition metal oxides were added to the same base glass, and their resistivity was in order: ρFe<ρV<ρMn. The relationships between the oxidation-reduction atmosphere of glass melting and the resistivity of glass were investigated. The conductivity types was confirmed to be electronic conductive by testing the Seebeck coefficient and Hall effect of glass. The resistivity of the developed SiO2- B2O3-P2O5-Al2O3-Fe2O3 electronic conductive glass system was reached to1010Ω·cmlevel.
Crack in microchannel plate (MCP) seriously reduces the mechanical and electrical properties of MCP. The mechanism of crack propagation in the chemical treatment process was revealed by studying the changes of crack morphology in acid-alkali etching and hydrogen reduction. The results show that during the acid-alkali etching process, the cracks on the channel material is dissolved by the dilute HNO3 and the cracks on the channel wall expands gradually under the etching of the NaOH solution. During the reduction process, cracks do not change significantly at the stage of heating. While at the stage of reaction with H2,the cracks are more easily expanded. The length of cracks does not change significantly after reduction. However, the surface near the cracks warps and the depth of cracks increases.
As an excellent two-dimensional electron multiplier device for transmission and enhancement of electronic image, microchannel plate (MCP) has the advantages of small volume, light weight, high resolution, high gain, low noise, low operating voltage, which plays an irreplaceable role in the fields of low-light-level night vision, space detection, nuclear detection, ultraviolet warning, medical image and so on. In recent years, with the continuous expansion of the application fields and the improvement of related manufacturing technologies, the performance requirements of MCP, especially the image quality, are getting higher and higher. 4G standard is the latest international requirements of image intensifier with FOM (Figure of Merit) reached more than 1800. Fixed pattern noise between multi-fibers of MCP is a common image defect. This defect not only increases the noise, reduces the signal-to-noise ratio, but also greatly interferes with the imaging quality, which has become a bottleneck problem restricting the improvement of FOM. This research is focused on the formation mechanism and control technology of fixed pattern noise between multi-fibers of MCP. The result shows that the formation mechanism of the fixed pattern noise between the multi-fibers is caused by the difference in microchannel structure, which leads to the difference in secondary electron yields between adjacent multi-fibers. Improving microchannel uniformity is an effective way to eliminate fixed pattern noise. The difference in microchannel structure is caused by the diameter deviation during fiber drawing. Through analysis and experimental measurement, it is found that the "heating-constant-cooling" zone of the drawing furnace has an optimal structure.
Microchannel-plate-based x-ray optics is designed based on the principle that the lobster eye reflects rather than refracts the object. In practice, the inner wall of the square channel is not absolutely smooth but a bit rough, which causes diffuse scattering of X-rays, resulting in an exponential decline in reflectivity. In the present work, we investigated the morphology of channel inner wall in the etching process and the diffusion depth of the elements at the interface between channel and wall. The diffusion layer is a network-like structure, with the thickness of more than 1μm. As the acid-etching continues, the elements of the channel material in the network are gradually dissolved, and the remaining channel wall materials become the skeleton. After a long time of etching, the inner wall surface is columnar and the roughness is gradually increased. This study provides some guidelines for the preparation of ultra-smooth reflective surfaces.
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.
Electron scrubbing is an effective method of degassing the microchannel plate(MCP). In the present work, we investigated the effect of electron scrubbing on MCP through characterizing the gain and dynamic range during and after the electron scrubbing. The gain of the MCP decreases to 25-30% of the initial gain with 28μA·h of electron scrubbing. The dynamic range can be broadened by electron scrubbing. The lower limit of the dynamic range of the MCP limited by the dark current of the test system does not change significantly and the upper limit of the dynamic response range is increased. The ratio of the upper limit before and after scrubbing is inversely proportional to that of the gain. The reasons for variation of gain and dynamic range were discussed, to provide reference for improving the performance of microchannel plate.
All-solid-state lasers have become one of the most promising research fields in the field of lasers because of their small size, high efficiency and convenient operation. All-solid-state lasers use semiconductor lasers as pump sources, however, Compared with gas lasers, solid-state lasers and fiber lasers, high-power semiconductor lasers have poor beam quality, thus limiting the progress of all-solid-state lasers. Therefore, improving the power and beam quality of semiconductor lasers has become a bottleneck in the development of all-solid-state lasers. The unit beam of the semiconductor laser is rectangular, so the beam needs to be shaped and focused to form a spot before being coupled to the laser medium. Due to its poor quality the spot center has a high optical energy density. When using LD end-pumped mode, the spot can easily destroy the film of the working medium end. In this paper, a uniform function describing the distribution of refractive index and the related parameters were used. And use this function to simulate and calculate the transmission characteristics of optical fiber. Based on the influence of fiber refractive index and core structure on the distribution of optical power in cross section, the homogenization of the LD beam spot is achieved by designing the core structure of optical fiber. This paper established optical fiber transmission model of light waves by using Matlab software and confirmed the influence of the refractive index distribution on the optical power distribution by using Comsol Multiphysics software.
Based on the high-resolution imaging property of the products of optical fiber material, a novel imaging system is proposed. The prototype of the system is made by coupling CCD chip(CMOS) and a large-scale optical fiber faceplate together. Firstly, the working principle and manufacturing process of large-scale optical fiber faceplate is described. Secondly, the effectiveness and practicability of the prototype of the system is verified by experiment. Finally, the potential application prospect of the imaging system is discussed. The theoretical analysis and experimental result show that the prototype works perfectly under high temperature and pressure condition and the resolution of the image that obtained by the imaging system is larger than 70 lp/mm, which can satisfy the basic imaging requirements in the research fields such as medical diagnosis, industrial detection and monitoring. Further, the novel imaging system provides a new approach for the application of optical fiber product in scientific research.
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