Owing to the characteristics of high frame frequency, large field of view, small size, streak tube with large work area and small size has been the essential component of the streak tube imaging lidar, and has immense potential in the field of aerospace, space exploration and underwater detection. In this paper, streak tube with a large spherically curved photocathode and small size has been modeled and simulated. The static temporal resolution reaches to 633fs when the effective working diameter of photocathode is 28mm, and its magnification of the image is 1.4. The quantitative relationship between the curvature radius and temporal distortion is analyzed, and temporal distortion can be compensated to minimum when curvature radium R=45mm. Guidance is provided for developing a femtosecond streak tube with large work area and small size for 3D imaging lidar.
A small size and long slit streak tube with high spatial resolution was designed and optimized. Curved photocathode and screen were adopted to increase the photocathode working area and spatial resolution. High physical temporal resolution obtained by using a slit accelerating electrode. Deflection sensitivity of the streak tube was improved by adopting two-folded deflection plates. The simulations indicate that the photocathode effective working area can reach 30mm × 5mm. The static spatial resolution is higher than 40lp/mm and 12lp/mm along scanning and slit directions respectively while the physical temporal resolution is higher than 60ps. The magnification is 0.75 and 0.77 in scanning and slit directions. And also, the deflection sensitivity is as high as 37mm/kV. The external dimension of the streak tube are only ∅74mm×231mm. Thus, it can be applied to laser imaging radar system for large field of view and high range precision detection.
The quantum efficiency characteristics of InP/In0.53Ga0.47As/InP photocathode which is one of the field-assisted negative electron affinity photocathodes with III-V compound semiconductor and works at transmission mode with a wide1 spectral response range from 1.0-1.7 μm were studied in this paper. Under certain field-assisted bias voltage, internal quantum efficiency at different wavelength versus structure parameters and doping concentration of the photocathode was simulated by the APSYS program. Results show that: First, internal quantum efficiency of the photocathode rises with the increasing of the field-assisted bias voltage. Second, the internal quantum efficiency gradually increases to a maximum at thickness=0.2um of P-InGaAs photo-absorbing layer and then reduces with the increasing of thickness. However, doping concentration of P-InGaAs photo-absorbing layer has little influence on it. Third, the internal quantum efficiency reduces with the increasing of thickness and doping concentration of P-InP photoelectron-emitting layer. The optimization results show that when the thickness of the photo-absorbing layer and the photoelectron-emitting layer are both 0.2 μm, and the doping concentration of the photo-absorbing layer and the photoelectron-emitting layer are about 1.5×1015 cm-3 and 1.0×1016 cm-3 respectively, under a certain field-assisted bias voltage, the line of the external quantum efficiency versus wavelength is ideal. Besides, the response time of photocathode can be reduced to less than 50 ps.
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