To ensure the expected output of the inertial confinement fusion (ICF) experiment, the laser performance operations model (LPOM)[
Collection Of theses on high power laser and plasma physics, Volume. 14, Issue 1, 31405(2016)
Simulation study of broadband long-pulsed amplification in high-power laser systems
Accurately and efficiently predicting the fundamental-frequency temporal shape of broadband long-pulsed lasers is very important in research on the properties of high-power laser amplifiers. In this study, we first propose that analytic electric polarization in the temporal domain is applied to broadband long-pulsed pulse amplification. We first verify the accuracy of this algorithm in the dozens of picoseconds range and the results are consistent with Miro software. Then we simulate the broadband long-pulsed amplification. The simulation results indicate that the front edge of the output pulse is more enlarged than the end edge owing to saturation and that the gain narrowing induces severe amplitude modulation. Analytic electric polarization in the temporal domain is effective and precise for investigating the broadband pulse amplification in the time scale from dozens of picoseconds to nanoseconds, and the computation time can be decreased by at least 4 orders of magnitude.
To ensure the expected output of the inertial confinement fusion (ICF) experiment, the laser performance operations model (LPOM)[
Broadband long-pulsed beams have not yet been introduced for investigation and use in domestic high-power laser facilities. Fresnel and Prop92 software mainly use the Frantz–Nodvik[
A numerical method has been developed because Miro’s broadband calculation mode computes amplification by considering both saturation and gain narrowing. The broadband amplification equations for a homogeneous line are[
In the time domain, the expected electric-field output modulated by a phase-modulation module can be expressed as[
The maximum difference between analytic electric polarization in the temporal domain and WFT is that the new algorithm aims to solve the signal property in the entire time domain. By following a previous report[
Finally, we simplify the broadband amplification of Eq. (
The conventional mathematical method can solve Eq. (
Miro’s[
To verify the accuracy of the new algorithm, Fig.
Figure 1.Temporal shape of the output pulse (30 ps).
In order to improve the focus uniformity of the near and far field further, and to suppress the SBS of large optical elements, the high-power laser facility should develop fundamental-frequency broadband long-pulsed laser amplification. In addition, one of the preconditions of analytic electric polarization in the temporal domain is that the pulse duration should be much larger than the dephasing time. Therefore, expanding the range of pulse durations to long pulses can make the calculation results more accurate. In order to satisfy the development requirement for high-power laser drivers using the new algorithm, we calculate the broadband amplification for 0.3 and 3 ns pulse widths. The following parameters are almost consistent with the parameters required by physical experiment in the laser facility.
The parameters for the 0.3 ns pulse width are as follows:
Figure 2.Temporal shape of the output pulse (0.3 ns).
The parameters of the 3 ns pulse width are as follows:
Figure 3.Temporal shape of the output pulse (3 ns).
The amplifiers constitute the most critical part of the laser chains, determining the output ability and level of the laser device. Therefore, an accurate amplified-transmission model of laser pulses in amplifiers and a high-efficiency algorithm are prerequisites to ensure accurate prediction and feedback. Although a broadband short-pulsed mode has been developed inside the Laser Magajoule device in France, the efficiency of the algorithm is quite low, and it cannot meet the engineering requirements of LPOM. Under this condition, it will be very important to make full use of the advantages of analytic electric polarization in the temporal domain, such as the wide range of pulse widths from dozens of picoseconds to a few nanoseconds, high efficiency, and high precision. The purpose of this paper, on one hand, is to prepare a preliminary theory for the broadband long-pulsed amplification and transmission in the SG-II facility; on the other hand, the purpose is to provide an efficient method of guidance for the implementation of online laser control and feedback.
In conclusion, the conventional method is very complicated and time-consuming for solving the problems of broadband pulse transmission and amplification for time scales from dozens of picoseconds to nanoseconds. Analytic electric polarization in the temporal domain was found to be more effective and appropriate, especially for long-pulsed amplification, and the new method can fully meet the engineering requirements of LPOM.
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Hongchao Hui, Junyong Zhang, Xinghua Lu, Jiachen Zhang, Xin Chen, Xiuqing Jiang, Baoqiang Zhu, Zunqi Lin. Simulation study of broadband long-pulsed amplification in high-power laser systems[J]. Collection Of theses on high power laser and plasma physics, 2016, 14(1): 31405
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Received: Oct. 22, 2015
Accepted: --
Published Online: May. 26, 2017
The Author Email: Hui Hongchao (13917856695@163.com)