For reducing the self-excited oscillation of end-pumped laser, the laser properties of the end-pumped Nd:YAG Q-switched laser is investigated with different Nd3+ ion doping concentration. The experiment results indicate that the output energy of the end-pumped Nd:YAG Q-switched laser is saturated when the pump energy is greater than 467mJ with 0.6% Nd3+ ion doping concentration, and the maximum output energy of 62.9mJ is generated under the pump energy of 498mJ, corresponding to the optical conversion efficiency of 12.6%. When the Nd3+ ion doping concentration decreases to 0.4%, the output energy of the end-pumped Nd:YAG Q-switched laser increases continuously with increasing pumping energy, the output energy is up to 64.7mJ under the pump energy of 498mJ, corresponding to the optical conversion efficiency of 13.0%, and no saturation occurs. By optimizing the structure parameters of the pump system, a 82.1mJ 10ns 1064nm laser is obtained under the pump energy of 527mJ, corresponding to the optical conversion efficiency of 15.6%. In view of the saturation of output energy in the end-pumped Nd:YAG Q-switched laser, Nd3+ ion doping concentration adjustment is carried out to reduce the pump end-face gain of laser medium, the self-excited oscillation can be effectively suppressed, an effective technical means for obtaining high-energy end-pumped Q-switched laser output is provided.
A new method of transmission efficiency and uniformity measurement for optical fiber image transmission component(OFITC) in visible band is proposed. The ray which emitted from the light source is received by a brightness sensor chip, which can convert the rough brightness into the visual brightness of specific area by weighted calculation. The visual brightness matrices of the designated area before and after placing the OFITC are named S1 and S2, respectively. After filtering, the transmission efficiency of OFITC is the quotient of the average values of S1 and S2. In order to calculate the light uniformity, S2 is divided into four parts which are circles or rings. The average of variances of these parts is defined as the uniformity. The brightness sensor chip required by this method is customized according to the size of optical fiber image transmission element. The experimental results can confirm the validity of this measurement method. At last, criteria for transmission efficiency and uniformity evaluation are proposed, which can greatly reduce the judgment error, improve the testing efficiency and save the cost of detection.
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.
Micro-nano project by studying the micro channel plate surface micro convex particle sizes can produce a phenomenon of point discharge which causes the field emission, and particles on the surface on the micro channel plate mechanism, then through metallographic microscope classification and testing for different particle morphology, finally three kinds of particle preparation is be determined. Through the study, by water to remove the ultrasonic repeatedly can get rid of polishing powder residue. And acid etching process of silica particles by adding alkali ultrasonic frequency and the use of high frequency ultrasound alternately can be completely removed. Then through evaporation before increasing ion bombardment can effectively control the micro convex particles which is produced after evaporation electrod. Through the study, by water to remove the ultrasonic repeatedly can get rid of polishing powder residue. And acid etching process of silica particles by adding alkali ultrasonic frequency and the use of high frequency ultrasound alternately can be completely removed. Then through evaporation before increasing ion bombardment can effectively control the micro convex particles which is produced after evaporation electrod.
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.
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