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Blind beam coke spots and dynamic control systems and methods based on plasma regulation

A plasma and dynamic control technology, applied in optics, optical components, instruments, etc., can solve problems such as limited degrees of freedom, great influence of focal spot shape, and difficult technical means to achieve continuous dynamic changes and enhanced flexibility sexual effect

Active Publication Date: 2021-02-26
LASER FUSION RES CENT CHINA ACAD OF ENG PHYSICS
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

This technical means can realize binary dynamic zoom, but there are three disadvantages: first, the dynamic zoom is a binary mode, and the degrees of freedom that can be designed are limited, which cannot meet the requirements of complex dynamic focal spots; For the partition of the near field, the near field corresponding to the peak energy and power moment cannot cover the entire near field area, thus limiting the peak energy and peak power of the target; third, the F numbers of the beams that generate the two types of focal spots are different, so the focal spot Internal speckle characteristics are also different
There are three deficiencies in this technology: first, it is reflected in the highest requirement for beam uniformity at the initial moment of the pulse, and at this time the focused spot is for out-of-focus shooting, and the dynamic distortion and near-field inhomogeneity of the laser have an impact on the shape of the defocused focal spot Larger, which limits the performance of the initial focal spot; second, this scheme is a dynamic adjustment of the front-stage wavefront, which will have a certain impact on the transmission and frequency conversion of the beam, which limits the dynamic zoom of the beam to a certain extent. Third, this technical solution is also quite difficult in engineering implementation, which is reflected in the fact that the zoom speed puts forward almost strict requirements on the change speed of high voltage, which is difficult to achieve with the current technical means

Method used

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  • Blind beam coke spots and dynamic control systems and methods based on plasma regulation
  • Blind beam coke spots and dynamic control systems and methods based on plasma regulation
  • Blind beam coke spots and dynamic control systems and methods based on plasma regulation

Examples

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Embodiment 1

[0046] A beam focal spot shaping and dynamic control system based on plasma control, wherein the incident main laser light (1) passes through a focusing lens (3) and then is focused on a distant focal plane (4) to generate a beam focal spot. In order to achieve dynamic control of the focal spot of the beam, the system places a plasma optical device (2) constructed using plasma in the near-field or quasi-near-field area where the beam is focused, with continuous phase plates and dynamic characteristics. The dispersion properties of the volume are controlled by the density and thickness of the plasma optical device (2), and then according to the design theory of the continuous phase plate, according to the requirements of the dynamic evolution of the target focal spot, the phase distribution of the plasma formation is designed. And further decompose the plasma dynamic evolution function η(x 0 ,y 0 ,t), to realize the shaping of the continuous phase plate; at the same time, the...

Embodiment 2

[0054] In one embodiment the plasma optics (2) are placed in front of the focusing lens (3), as figure 1 shown. After the beam passes through the plasma optical device (2), the phase distribution introduced by it is:

[0055]

[0056] Where λ is the beam wavelength, n e (x 0 ,y 0 ,t) is the plasma density distribution, x 0 ,y 0 is the near-field coordinates of the beam, t is the time, n c is the plasma critical density for wavelength λ, l(x 0 ,y 0 ) is the thickness of the plasma layer. The intensity distribution of the beam focal spot corresponding to the phase distribution of formula (1) is

[0057]

[0058] "F" in formula (2) represents Fourier transform, c' is a constant term, x, y are the far field coordinates, and E is the near field amplitude of the beam.

[0059] According to the design theory and method of the continuous phase plate in the foregoing embodiment 1, the phase distribution of the near field of the beam can be adjusted The focal spot I(x,...

Embodiment 3

[0062] In this embodiment, it is assumed that the focal spot dynamic I objn (x,y,t n ) evolution requires a specific parameter design method under the condition of linearly decreasing with time, at this time for A specific design is carried out, one of the design results is as follows: the initial phase distribution Such as image 3 As shown, the dynamic function η(x 0 ,y 0 ,t) is expressed as

[0063]

[0064] where T 0 is the rate parameter of the linear change of the focal spot.

[0065] Such as Figure 4 simulated in image 3 The initial phase of and the morphological characteristics of the focal spot under the dynamic function of formula (5), where in (a)-(f), the values ​​of t are 0, 0.1T 0 , 0.2T 0 , 0.3T 0 , 0.4T 0 , 0.5T 0 , at this time, the near-field moment has the characteristics of full use of energy and overall random phase, and the corresponding focal spots have the same shape, and the major axis sizes are 1000 μm, 900 μm, 800 μm, 700 μm, 600 ...

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Abstract

The invention discloses a beam spot shaping and dynamic control system and method based on plasma control, belonging to the technical field of laser beam control. In view of the dynamic requirements of rapid changes in the shape and size of the focal spot of the beam, the system introduces a plasma device in the near-field or quasi-near-field area where the beam is focused, and utilizes the dispersion properties of the plasma to control its density and thickness to achieve The shaping function of the continuous phase plate; using the dynamic properties of the plasma, the function of forming a dynamic wavefront through its physical effects such as diffusion and recombination, realizes the dynamic shaping of the beam focal spot. The invention can realize the continuous change of the shape of the focal spot, and the whole process and the near field have the characteristics of full use of energy and overall random phase, so that the performance of the beam is not affected during the whole dynamic process; because the plasma medium has a very high The damage threshold can be applied anywhere in the high-power / high-energy laser device, which enhances the flexibility of the method application.

Description

technical field [0001] The invention belongs to the technical field of laser beam control, in particular to a system and method for beam focal spot shaping and dynamic control based on plasma control. Background technique [0002] In the direct drive research of inertial confinement fusion, the irradiation non-uniformity of the surface of the capsule and the cross energy transfer of the ablation plasma region are two important issues affecting the physical performance, and their requirements on the laser focal spot are contradictory, so the proposed The idea of ​​dynamic focal spot is used to balance these two physical processes (I V Igumenshchev, D H Froula, D HEdgell et al, Laser-beam zooming to mitigate crossed-beam energy losses indirect-drive implosion.Physics Review Letters.2013,110:145001 ). [0003] The device to realize the dynamic focal spot must have the response speed of the nanosecond level and have enough variation. This type of device is not common. At presen...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): G02B27/09
CPCG02B27/0927G02B27/0938
Inventor 李平魏晓峰张小民王伟靳赛周丽丹冯斌朱德燕柴向旭
Owner LASER FUSION RES CENT CHINA ACAD OF ENG PHYSICS