| Inertial confinement fusion is a method that uses particle inertia to constrain particles to achieve a controlled nuclear fusion reaction.In order to achieve the ignition conditions of inertial confinement fusion,a variety of drive source technologies have been developed,the most important of which is high-power laser drive technology.The output capability of high power laser drivers is an important indicator for evaluating the overall performance of high power laser drives.The output capability of the laser driver is mainly determined by the gain capability and load capacity of the system.The former is mainly determined by the energy conversion efficiency and various types of losses of the system,while the latter depends mainly on the damage threshold of key components in the system and the uniformity of the near-field distribution of the beam..The energy conversion efficiency of the amplification system(mainly including the energy storage efficiency of the amplifier,the energy extraction efficiency of the amplifier,and the frequency conversion efficiency)is the key to determining the system performance and price ratio.Therefore,improving system energy conversion efficiency is a key issue to be solved in designing high-power laser systems.A series of theoretical and experimental results show that compared with narrow-band pulse transmission amplification,the use of broadband laser pulses can not only inhibit autofocus growth,improve near-field uniformity,improve the overall performance of high-power laser drivers,but also improve the performance of neodymium glass amplifiers.Energy extraction efficiency.The paper mainly includes the following three parts:1.The narrow-band laser pulse amplification theory based on Frantz-Nodvik model is combed,and the difference of the amplification process of narrow-band laser pulse in uniform widened medium and non-uniform widened medium is analyzed,and the model is extended to deal with broadband(or multi-frequency).On the amplification of laser pulses,an amplification model capable of describing broadband(or multi-frequency)laser pulses in uniform widening and non-uniform widening media was established.Then the pulse amplification theory based on Maxwell equation is introduced.The amplification model of broadband chirped laser pulse in uniform widened medium is deduced.The processing method of wideband chirped laser pulse amplification in non-uniform widened medium is discussed.2.The energy level and spectral structure of Nd3+ions in bismuth glass are introduced.The mechanism of uniform broadening of spectral lines and non-uniform broadening of spectral lines in bismuth glass is analyzed.Combined with the theory of pulsed laser amplification,a theoretical model of the wide-band laser amplification of neodymium glass was established,and a program for calculating the narrow-band,instantaneous broadband(or multi-frequency)amplification process and output energy,time waveform and spectrum of the bismuth glass was prepared.3.Using the written Nd-glass narrow-band and wide-band laser pulse amplification program,the time waveform and spectral characteristics of narrow-band pulse and wide-band(or multi-frequency)pulses in bismuth glass were simulated and analyzed.The energy extraction efficiency and input of bismuth glass amplifier were studied.The relationship between luminous flux,laser bandwidth(or wavelength distribution),pulse width and other factors. |
