CN113687460B

CN113687460B - Acoustic wave plasma grating generation method with fast boundary extension

Info

Publication number: CN113687460B
Application number: CN202110863559.7A
Authority: CN
Inventors: 吴朝辉; 左言磊; 曾小明; 李钊历; 王晓东; 王逍; 母杰; 胡必龙
Original assignee: Laser Fusion Research Center China Academy of Engineering Physics
Current assignee: Laser Fusion Research Center China Academy of Engineering Physics
Priority date: 2021-07-29
Filing date: 2021-07-29
Publication date: 2023-06-06
Anticipated expiration: 2041-07-29
Also published as: CN113687460A

Abstract

The invention discloses a method for generating an acoustic wave plasma grating with a fast-extending boundary, which belongs to the field of plasma optical devices and comprises the following steps: firstly, two long pulse lasers are utilized to interfere in gas, and a high-frequency gas grating structure is generated by the electrostriction effect in the gas; then, the gas grating is ionized by the short pulse laser to generate a plasma grating, and the boundary of the plasma grating is rapidly extended along with the ionization pulse; the method of the invention can obtain the plasma grating with better stability and greatly improved diffraction efficiency, and the obtained plasma grating can realize the extension of the boundary along with the short pulse at the speed of light, and can be used for dynamic regulation and control of laser compression, broadening, high-speed optical switches and the like.

Description

Acoustic wave plasma grating generation method with fast boundary extension

Technical Field

The invention relates to the field of plasma optical devices, in particular to a method for generating an acoustic wave plasma grating with a fast extending boundary.

Background

Plasma optics have important application in intense lasers. The plasma has an irreplaceable effect in the field of strong lasers due to the high damage threshold of the plasma. Currently, plasma optical elements such as plasma mirrors, plasma lenses, plasma gratings and the like are widely applied to the field of intense laser. The plasma grating is an important optical component and can realize the functions of filtering, reflecting, polarization state conversion, hologram and the like of strong laser.

At present, two main ways of generating plasma gratings are: two laser beams are interfered in plasma, and a plasma grating is generated by utilizing the prime power action of a laser field. The other is that two beams of laser are interfered and ionized in a medium, a plasma grating is formed by different ionization rates of a light field with strong and weak distribution on the medium, and the generated plasma grating can generate diffraction effect on the laser and can control the laser to a certain extent.

However, both methods have a diffraction efficiency of 20% or less, i.e., there is a problem of low diffraction. In addition, the first method has the problem that the influence of plasma instability is large, and the second method has the problem that the grating modulation depth generated by interference laser is insufficient.

Disclosure of Invention

The present invention is directed to a method for generating an acoustic wave plasma grating with a fast boundary extension, so as to solve the above-mentioned problems.

In order to achieve the above purpose, the technical scheme adopted by the invention is as follows: a method for generating an acoustic wave plasma grating with a fast extending boundary comprises the following steps: firstly, two long pulse lasers are utilized to interfere in gas, and high-frequency sound waves are generated by the electrostriction effect in the gas; then, the gas grating is ionized by the short pulse laser to generate a plasma grating, and the boundary of the plasma grating is rapidly extended along with the ionization pulse.

As a preferable technical scheme: the long pulse laser is laser with the half-width of the laser pulse width being more than 1 ns.

As a preferable technical scheme: the short pulse laser is laser with the half-width of the laser pulse width less than 100 fs.

One of the cores of the acoustic wave plasma grating generating method of the invention is: the high-frequency sound wave in the laser ionized gas is adopted to generate the plasma grating, and compared with the mode that the existing laser generates the grating in the plasma, the optical plasma grating has better stability. The diffraction efficiency of the sound wave reported in the prior literature can reach more than 95%, and the diffraction characteristic of the sound wave can be kept to the maximum extent by adopting femtosecond pulse ionization sound wave energy, so that the diffraction efficiency of the plasma grating is greatly improved, namely, the diffraction efficiency of the plasma grating can reach approximately 95%; secondly, the second core is to adopt a plasma grating with a boundary extending along with the short pulse at the speed of light generated by the short pulse ionization sound wave so as to realize dynamic regulation and control of laser; when the boundary of the grating extends at the speed of light, dynamic diffraction and reflection of laser can be realized, and the grating can be used for compression, broadening and high-speed optical switches of laser.

The high-frequency sound wave according to the present invention is generated by interference (brillouin effect) of two long pulse lasers in a gas. Brillouin effect is widely present in solids, liquids and gases, where high frequency acoustic waves are a byproduct of brillouin efficiency; the "high frequency sound wave" of the present invention means that the frequency is 10 unless otherwise specified ⁹ Sound waves above Hz; the main principle is that laser generates stable strong and weak distribution area by interference in gas, and then periodic is generated by electrostriction effectThe intensity distribution of the gas is formed to form a gas grating. When the included angle of the two laser beams is alpha, the period of the generated high-frequency sound wave is lambda/2 sin (alpha/2), wherein lambda is the wavelength of the laser; the period of the sound wave can be adjusted from lambda/2 to infinity by adjusting the included angle alpha of the two beams of light.

Compared with the prior art, the invention has the advantages that: the method of the invention can obtain the plasma grating with better stability and greatly improved diffraction efficiency, and the obtained plasma grating can realize the extension of the boundary along with the short pulse at the speed of light, and can be used for dynamic regulation and control of laser compression, broadening, high-speed optical switches and the like.

Drawings

FIG. 1 is a schematic diagram of the present invention;

fig. 2 is a light path diagram for implementing the present invention.

In the figure: 1. long pulse laser (dashed rectangle); 2. high frequency sound waves (dashed rectangular array); 3. short pulse laser (solid rectangular box); 4. plasma gratings (solid rectangular array); 5. a beam splitter; 6. 7 and 8 are light guide lenses; 9. 10 are long pulse focusing lenses; 11. a short pulse laser focusing lens; alpha is an included angle of two long pulse lasers, and theta is an included angle of the long pulse lasers and the short pulse lasers; in the figure, the arrow indicates the propagation direction of the laser light.

Detailed Description

The invention will be further described with reference to the accompanying drawings.

Examples:

in the embodiments described in the following description of the embodiments,

the long pulse laser refers to laser with the half width of the laser pulse width being more than 1 ns;

the short pulse laser refers to laser with the half-width of the laser pulse width less than 100 fs;

referring to fig. 1, a method for generating an acoustic wave plasma grating with fast boundary extension includes the following steps:

two long pulse lasers 1 with an included angle alpha generate high-frequency sound waves 2 with a period of lambda/2 sin (alpha/2) in gas, short pulse lasers 3 ionize the sound waves to generate plasma gratings 4, and the boundaries of the generated plasma gratings extend along with 4 at the speed of light because the short pulse lasers 3 are short pulse lasers;

referring to fig. 2, a long pulse laser 1 passes through a spectroscope 5 and is split into two beams in equal proportion, and then the two beams of laser are focused into gas through

light guide lenses

6, 7 and 8 and long

pulse focusing lenses

9 and 10 respectively to generate high-frequency sound waves; finally, the short pulse laser 3 is focused to the ionized acoustic wave in the gas through the short pulse laser focusing lens 11 to generate a plasma grating 4 with a rapidly extending boundary.

The foregoing description of the preferred embodiments of the invention is not intended to be limiting, but rather is intended to cover all modifications, equivalents, and alternatives falling within the spirit and principles of the invention.

Claims

1. A method for generating an acoustic wave plasma grating with a fast-extending boundary is characterized by comprising the following steps: firstly, two long pulse lasers are utilized to interfere in gas, and a high-frequency gas grating structure is generated by the electrostriction effect in the gas; then, the gas grating is ionized by the short pulse laser to generate a plasma grating, and the boundary of the plasma grating is rapidly extended along with the ionization pulse, wherein the high frequency refers to the frequency of 10 ⁹ Hz or above.

2. The method for generating the acoustic wave plasma grating with the rapid extension of the boundary as claimed in claim 1, wherein: the long pulse laser is laser with the half-width of the laser pulse width being more than 1 ns.

3. The method for generating the acoustic wave plasma grating with the rapid extension of the boundary as claimed in claim 1, wherein: the short pulse laser is laser with the half-width of the laser pulse width less than 100 fs.