Generation Of Fast Forward Electric Pulse And Its Application In Streak Cameras

Semi-insulating GaAs material has many advantages, such as short carrier life,high dark resistance, high carrier mobility and other characteristics, using GaAs photoconductive semiconductor switches (GaAs PCSS’s) to obtain ultra-fast pulse is an excellent choice.The photoelectric response of GaAs PCSS’s are very fast, the output electrical pulse is in consistent with optical pulse in the linear operation mode.Using the linear relationship between the electric pulse and the optical pulse, the ultrafast pulse of femtosecond laser can be photoelectrically converted to obtain ultrafast electric pulse. GaAs PCSS’s have the characteristic of obtaining ultrafast electric pulse, which have significance research value and great impact in many aspects, such as the synchronous scan camera, ultra wide impulsive source, THz electromagnetic wave emission source, high current ignition device, digital-analog conversion, optical inspection and impulse radar and so on.The streak camera is a diagnostic tool with high temporal resolution, which plays an important role in the study of ultrafast processes such as inertial confinement fusion (ICF), et al. The performance of the scanning circuit determines the time resolution of streak cameras,which has a major impact on the performance of cameras. In this paper, the scanning circuit of streak camera is described, the scanning circuit based on GaAs PCSS’s are studied, and a GaAs photoconductive switch is used to realize the positive and negative symmetry output pulse.The main task of this thesis is using GaAs PCSS’s to realize the positive and negative symmetry output pulse and test its performance. A GaAs photoconductive switch with a gap of 3.5 mm triggered by a femtosecond laser, the output characteristics of the rising edge and the switching voltage transmission efficiency of the electric pulse are studied under the condition of different pulse energy, storage capacitance, bias voltage and the trigger mode with front trigger and back trigger.When the bias voltage of ± 2000 V and the laser pulse of 102μJ , a positive and negative bilateral electrical pulse with 174 ps rise time and 90 % voltage transmission efficiency output symmetrically is achieved. Meanwhile the pulse rise slope along the linear area is 8.1kV/ns, and the voltage value of the linear region is in the range of 692.93V～1745.73V which is greater than 1000V,the results meet the requirements of the scanning voltage signal of femtosecond streak camera. In addition,the output waveform of the switch in 1kHz repetition frequency of 10 times laser is analyzed,and explains the reason of the photoconductive switch operation mode is in linear mode. At the same time, the jitter is evaluated with switching frequency of 1kHz, and the trigger jitter is less than 100 fs is obtained. Finally, the effect of switches with different gap width on the pulse output characteristics is investigated.