Method and facility for nanosecond laser spatial-temporal control in a direct-drive laser facility with double-cone ignition scheme

Patent metadata

Field	Value
Publication number	US-2025364766-A1
Application number	US-202519291496-A
Country	US
Kind code	A1
Filing date	Aug 5, 2025
Priority date	Jan 30, 2024
Publication date	Nov 27, 2025
Grant date	—

Abstract

A nanosecond laser spatial-temporal control method for a direct-drive laser facility based on Double-Cone Ignition, while satisfying the near-isentropic compression waveform required for driving implosion, redistributes the temporal waveforms of all sub-beams in the facility. A small portion of the beams are used to generate a low-energy foot pulse, which is focused on a larger target surface. Under the action of the low-energy foot pulse, the target surface contracts slowly inward. By the end of the duration of the low-energy foot pulse, the target surface has contracted to a smaller size. At this moment, the remaining majority of the beams are used to generate the main drive pulse, which is focused on this smaller target surface, thereby achieving zooming.

First claim

We claim:

1 . A nanosecond laser spatial-temporal control method based on a Double-Cone Ignition direct-drive laser facility, comprising:
redistributing time-power curve of all nanosecond laser pulses in the Double-Cone Ignition direct-drive laser facility under a condition of meeting near isentropic compression waveforms for driving implosion; generating a low-energy foot pulse by using a small part of beams, focusing the low-energy foot pulse on a larger target surface, and enabling the larger target surface to slowly shrink inward under action of the low-energy foot pulse and shrink to a smaller target surface at an end of a duration of the low-energy foot pulse; and generating a main drive pulse by using most of a remaining beams, and focusing the main drive pulse on the smaller target surface, thereby achieving zooming.

2 . The nanosecond laser spatial-temporal control method based on a Double-Cone Ignition direct-drive laser facility according to claim 1 , wherein a duration of the near isentropic compression waveforms for driving implosion is 0−τ, the duration of the low-energy foot pulse is 0−t d , a duration of the main drive pulse is t d −τ, and t d corresponds to a corresponding moment when a target pellet converges from an initial radius R t to 0 . 7 R t .

3 . The nanosecond laser spatial-temporal control method based on a Double-Cone Ignition direct-drive laser facility according to claim 1 , wherein a number of the all nanosecond laser pulses in the Double-Cone Ignition direct-drive laser facility is n beams; and then, in the case of ensuring a balance of intensity of a power sum of n/2 beams of nanosecond laser pulses on upper and lower cones, a time waveform of each beam is redesigned so that a sum of the n/2 beams of the nanosecond laser pulses satisfies the near isentropic compression waveforms for driving implosion.

4 . The nanosecond laser spatial-temporal control method based on a Double-Cone Ignition direct-drive laser facility according to claim 1 , wherein, for n/2 beams of nanosecond laser pulses on a single cone, the low-energy foot pulse is generated by using a small portion of beams that are m beams and focused on a larger target surface;
on a target surface with an initial radius of R t , the energy of the low-energy foot pulse is converted into kinetic energy of a target shell, and the target surface with the initial radius of R t slowly shrinks inward; and when the target surface converges to a smaller target surface with a target surface radius of R b at a moment t d , R b /R t =0.7, and (n/2−m) beams are left, that is, a high-energy main drive pulse generated by most of the remaining beams is focused on the target surface with the radius of R b , thereby achieving zooming.

5 . The nanosecond laser spatial-temporal control method based on a Double-Cone Ignition direct-drive laser facility according to claim 1 , wherein m beams of nanosecond laser pulses for generating the low-energy foot pulse should satisfy the following conditions:
each nanosecond laser pulse is within a safe energy density of 4 J/cm 2 ; a load of m beams of nanosecond laser pulses for generating the low-energy foot pulse is equal to a load of (n/2−m) beams of nanosecond laser pulses for generating the high-energy main drive pulse; and the m beams of nanosecond laser pulses for generating the low-energy foot pulse are arranged as much as possible on a ring with an smallest comprised angle to a polar axis to improve the irradiation uniformity of drive laser at an early stage on the target surface.

6 . A facility for implementing the nanosecond laser spatial-temporal control method based on a Double-Cone Ignition direct-drive laser facility according to claim 1 , comprising:
a spectral dispersion grating ( 2 ), a transmission amplification assembly ( 3 ), a frequency-doubling and tripling crystal ( 4 ), a continuous phase plate ( 5 ), a polarization control plate ( 6 ), a focus lens ( 7 ), and a target surface ( 8 ), wherein the spectral dispersion grating ( 2 ), the transmission amplification assembly ( 3 ), the frequency-doubling and tripling crystal ( 4 ), the continuous phase plate ( 5 ), the polarization control plate ( 6 ), the focus lens ( 7 ), and the target surface ( 8 ) are sequentially arranged along a transmission direction of a front-end seed source ( 1 ), a seed light output from the front-end seed source ( 1 ) enters the transmission amplification assembly ( 3 ) after passing through the spectral dispersion grating ( 2 ) to amplify a beam diameter and energy; fundamental frequency light is converted into triple frequency light through the frequency multiplication crystal ( 4 ); and a far-field focal spot is shaped into a focal spot of a specified shape and size through the continuous phase plate ( 5 ), passes through the polarization control plate ( 6 ), and is then focused by the focusing lens ( 7 ) on the far-field target surface ( 8 ) to form a shaped focal spot.

7 . The facility according to claim 6 , wherein n beams of nanosecond laser pulses are generated by different front-end seed sources ( 1 ), so that the time and frequency domain characteristics of each light beam can be independently controlled.

8 . The facility according to claim 6 , wherein the front-end seed source ( 1 ) comprises:
a seed light source laser ( 11 ), a time pulse shaping unit ( 12 ), and a phase modulation unit ( 13 ), wherein the seed light source laser ( 11 ), the time pulse shaping unit ( 12 ), and the phase modulation unit ( 13 ) are placed in sequence on the same optical axis, the seed light source laser ( 11 ) is configured to tune a central wavelength; the time pulse shaping unit ( 12 ) is configured to accurately control a time-power curve, thereby achieving high-precision control of the generation time for each beam of nanosecond laser pulse and a high-precision time delay adjustment capability, wherein the control precision is at a picosecond scale; and the phase modulation unit ( 13 ) is configured to control a spectrum.

9 . The facility according to claim 8 , wherein a speckle structure that varies over time is obtained by combining the spectral dispersion grating ( 2 ) with the phase modulation unit ( 13 ) in the front-end seed source ( 1 ), thereby smoothing a focal spot evenly within a specific time.

10 . The facility according to claim 8 , wherein a target focal spot of each beam of nanosecond laser pulse on the continuous phase plate ( 5 ) used during transmission has a different size; for a low-energy foot pulse, the target focal spot has a size slightly smaller than that of a target surface with an initial radius of R t to provide better illumination uniformity; and for a high-energy main drive pulse, the target focal spot has a size slightly smaller than a target surface with a radius of R b to reduce the energy transfer of crossed light beams and improve the laser-target coupling efficiency.

11 . The facility according to claim 8 , wherein, for different nanosecond laser pulses, a polarized state of the polarization control plate ( 6 ) may be linearly polarized light along a tangent or normal direction of a position on a ring where the light beam is located, or left-handed or right-handed circularly polarized light, or elliptically polarized light, thereby reducing the correlation between sub-beams.

12 . The facility according to claim 8 , wherein the target surfaces ( 8 ) of the m beams of low-energy foot pulses and (n−m) beams of high-energy main drive pulses are different in position, and the target surfaces ( 8 ) of the (n−m) beams of high-energy main drive pulses are positioned slightly behind.

Assignees

• Shanghai Inst Optics & Fine Mech Cas

Inventors

• Fan Wei
• Zhang Yujia
• Sun Mingying
• Lu Xinghua
• Wang Jiangfeng
• Wang Xiaochao
• Zhang Yanli
• Jiang Xiuqing
• Qiao Zhanfeng

Classifications

• H01S3/005

  Optical devices external to the laser cavity, specially adapted for lasers, e.g. for homogenisation of the beam or for manipulating laser pulses, e.g. pulse shaping (shaping laser beam for working metal or other materials B23K26/06; optical elements, systems or apparatus in general G02B) · CPC title

• H01S3/0057 Primary

  Temporal shaping, e.g. pulse compression, frequency chirping (soliton generation and propagation G02F1/3513, H01S3/063 and H01S3/108) · CPC title

• H01S3/10092

  Coherent seed, e.g. injection locking · CPC title

• H01S3/10053

  Phase control · CPC title

• H01S3/10061

  Polarization control · CPC title