A system and method for controlling the polarization state of a high-power laser pulse

Abstract

This invention belongs to the field of laser pulse polarization control technology, and discloses a high-intensity laser pulse polarization state control system and method. The system includes a laser, a polarization controller, a processing device, and a central control unit. The laser generates and outputs laser pulses; the polarization controller receives the laser pulses emitted by the laser and rapidly adjusts their polarization direction; the processing device applies the polarization-adjusted laser pulses to the processing material; and the central control unit is electrically connected to the laser, polarization controller, and processing device to achieve synchronous control of these components. This invention, employing the aforementioned high-intensity laser pulse polarization state control system and method, achieves a technological breakthrough in ultra-intense laser polarization control through the innovative application of plasma media, possessing high tolerance, high precision, and adaptability, filling a technological gap in this field.

Description

Technical Field

[0001] This invention relates to the field of laser pulse polarization control technology, and in particular to a system and method for controlling the polarization state of a strong laser pulse. Background Technology

[0002] The polarization state of a laser beam is one of its most important characteristics, playing a crucial role in many applications. For example, in laser processing, optical communication, quantum information processing, inertial confinement fusion (ICF), and ultrafast laser physics, precise control of the laser's polarization state (such as linear, circular, or elliptical polarization) has a decisive impact on the efficiency, accuracy, and stability of experimental or industrial processes. With the rapid development of laser technology, especially the emergence of ultra-intense and ultra-short pulse lasers, the demand for laser polarization control is increasing daily.

[0003] Traditionally, the control of laser polarization states has relied primarily on optical components such as polarizers, waveplates, electro-optic modulators (e.g., Pockels cells), or magneto-optic modulators. These methods perform well under low-intensity lasers, enabling high-precision polarization control. However, when the laser intensity exceeds a certain threshold, the limitations of traditional optical devices become apparent. High-power lasers have extremely high electric field strengths, which can easily cause nonlinear absorption, thermal effects, or even direct breakdown in optical media (such as crystals and glass), thereby damaging polarization control devices. For example, commonly used quartz waveplates or BBO electro-optic crystals may fail rapidly under ultra-intense lasers. When powerful lasers interact with optical media, they may introduce nonlinear effects such as self-focusing and self-phase modulation, leading to decreased polarization control accuracy and even damaging beam quality. Some polarization control elements (such as waveplates) are typically only suitable for specific wavelength ranges, making it difficult to meet the needs of ultra-wideband or tunable lasers.

[0004] Due to the aforementioned limitations, traditional optical polarization control methods are difficult to apply to ultra-intense laser systems, thus necessitating the exploration of new polarization control mechanisms. Plasma, as the fourth state of matter, has no damage threshold. Therefore, plasma can be used as a medium for controlling ultra-intense lasers. Current research explores methods for controlling laser polarization using plasma, such as: achieving polarization rotation through magnetized plasma (similar to the Faraday effect); achieving polarization-selective reflection / transmission using plasma gratings or density modulation structures; and controlling the laser polarization state based on plasma channels or self-generated electromagnetic fields. However, existing technologies still suffer from low control efficiency and insufficient stability, highlighting the urgent need for an efficient, stable, and suitable polarization control method for ultra-intense lasers. Summary of the Invention

[0005] The purpose of this invention is to provide a system and method for controlling the polarization state of a strong laser pulse. By adjusting the background magnetic field strength and plasma density, the polarization plane of a linearly polarized strong laser pulse can be rotated in the forward or reverse direction, and the rotation angle is completely controllable. The system can also convert a linearly polarized strong laser pulse into a left-handed circularly polarized laser pulse. Furthermore, the system can separate the left-handed and right-handed circularly polarized components in the linearly polarized strong laser pulse, so that the transmitted wave is a left-handed circularly polarized wave and the reflected wave is a right-handed circularly polarized wave, or the transmitted wave is a right-handed circularly polarized wave and the reflected wave is a left-handed circularly polarized wave.

[0006] To achieve the above objectives, the present invention provides a high-power laser pulse polarization state control system, comprising a laser, a polarization controller, a processing device, and a central control unit;

[0007] The system comprises a laser for generating and outputting laser pulses; a polarization controller for receiving laser pulses emitted by the laser and rapidly adjusting the polarization direction of the laser pulses; a processing device for applying the laser pulses adjusted by the polarization controller to the processing material; and a central control unit electrically connecting the laser, polarization controller, and processing device to achieve synchronous control of the laser, polarization controller, and processing device.

[0008] Preferably, in order to achieve polarization adjustment of the ultra-intense laser pulse by the polarization controller, magnetized plasma is introduced, and the specific process is as follows:

[0009] (1) Decompose linearly polarized laser into left-hand circularly polarized laser and right-hand circularly polarized laser;

[0010] (2) Left-handed and right-handed circularly polarized lasers have different dielectric constants in magnetized plasma, as shown below:

[0011]

[0012] Where, ε R ε is the dielectric constant of right-handed circularly polarized laser light; L ω is the dielectric constant of the left-hand circularly polarized laser; ω is the laser frequency. is the plasma frequency; e is the electron charge; m e For electron mass; n e The plasma density; denoted as electron cyclotron frequency; B0 as background magnetic field strength; and c as speed of light.

[0013] A method for controlling the polarization state of a high-power laser pulse, specifically including:

[0014] Control of the polarization plane rotation of linearly polarized lasers, i.e., Faraday forward rotation, is shown below:

[0015] when At that time, ε L >ε RWhen the phase velocity of a right-handed spiral wave is greater than that of a left-handed spiral wave, the polarization direction rotates in the positive direction.

[0016] Among them, B c The critical magnetic field for electron cyclotron resonance; n c Given the critical plasma density; calculate the rotation angle as follows:

[0017]

[0018] Therefore, the rotation angle of the polarization plane can be controlled by adjusting the plasma density and the background magnetic field strength;

[0019] Set the PIC particle simulation parameters as follows: B0 = 2 × 10 3 T, n e =0.1n c ≈10 26 m -3 I0 = 1.24 × 10 17 W / cm 2 λ = 1.06 μm; where I0 is the peak laser intensity; λ is the laser wavelength; B c ≈10 4 T, n c ≈10 27 m -3 The incident wave is a linearly polarized pulsed laser in the y-direction; the two-dimensional simulation range is 120 μm × 40 μm; the plasma distribution range is 50 μm. <x<70μm;

[0020] Laser pulse, as shown below:

[0021]

[0022] Where I is the instantaneous laser intensity; w is the laser beam waist radius; y is the transverse spatial coordinate; t is the time variable; τ is the laser pulse width; let w = 10 μm, τ = 30 fs, and the laser be incident perpendicularly from the x = 0 end;

[0023] After the laser pulse is emitted from the plasma, the rotation angle of the polarization plane is obtained from formula (3). Among them, E z and E y These represent the components of the laser pulse electric field in the z and y directions, respectively.

[0024] Preferably, the linearly polarized laser is converted into a left-handed circularly polarized laser, as shown below:

[0025] From formula (1), we know that when When the denominator is approximately 0, the right-handed circularly polarized wave undergoes resonant absorption, and thus only the left-handed circularly polarized wave remains of the transmitted wave.

[0026] Preferably, the linearly polarized laser polarization plane rotation is controlled, i.e., Faraday inverse rotation, as shown below:

[0027] when At that time, ε R >ε L >0, the phase velocity of the left-handed wave is greater than that of the right-handed wave, so the polarization direction rotates in the opposite direction;

[0028] Set PIC particle simulation parameters: B0~8×10 4 T, the other parameters are the same as above;

[0029] After the laser pulse is emitted from the plasma, its polarization plane rotates in the opposite direction. The rotation angle can be obtained from formula (3).

[0030] Preferably, the linearly polarized laser pulse is decomposed into left-handed and right-handed laser pulses, i.e., left-handed wave is reflected and right-handed wave is transmitted, as shown below:

[0031] when hour, It cannot propagate in the plasma and is therefore reflected at the plasma surface; the transmitted wave is only a right-handed wave.

[0032] Preferably, electromagnetic wave shielding is provided as follows:

[0033] when At this time, neither left-handed nor right-handed spiral waves can propagate in the plasma and are reflected at the plasma surface.

[0034] Preferably, the linearly polarized laser pulse is decomposed into left-handed and right-handed laser pulses, i.e., right-handed waves are reflected and left-handed waves are transmitted, as shown below:

[0035] when 1-B0 / B c <n e / n c <1+B0 / B c At that time, ε R <0, right-handed wave is reflected; ε L >0, the transmitted wave is a left-handed spiral wave.

[0036] Therefore, this invention employs the aforementioned high-intensity laser pulse polarization state control system and method. By introducing plasma as the control medium, it solves the problems of traditional optical components being easily damaged and exhibiting significant nonlinear effects under ultra-intense lasers, achieving a technological breakthrough in ultra-intense laser polarization control. It combines high tolerance, high precision, and adaptability, filling a technological gap in this field. It enables reliable control of the polarization state of high-intensity lasers and possesses efficient and stable polarization control capabilities. This provides a new solution for scenarios requiring high-intensity polarization control, such as laser processing, quantum information processing, and optical communication, improving the efficiency, precision, and stability of related applications.

[0037] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0038] Figure 1 This is a PIC particle simulated plasma distribution diagram in an embodiment of the present invention;

[0039] Figure 2 In the embodiments of the present invention, B0~2×10 3 T, n e =0.1n c ≈10 26 m -3 I0 = 1.24 × 10 17 W / cm 2 The simulation results are shown in the figure when λ = 1.06 μm.

[0040] Figure 3 These are B0-10 in the embodiments of the present invention. 4 The simulation results at time T are shown in the figure; where (a) is the simulation result and (b) is the electric field of the transmitted laser.

[0041] Figure 4 In the embodiments of the present invention, B0~8×10 4 Simulation results at time T;

[0042] Figure 5 n is the embodiment of the present invention e =10n c ≈10 28 m -3 B0~5×10 4 Simulation results at T = 100fs;

[0043] Figure 6 n is the embodiment of the present invention e =10n c ≈10 28 m -3 B0~5×10 4 Simulation results at T, 240fs;

[0044] Figure 7 n is the embodiment of the present invention e =10n c ≈10 28 m -3 B0~5×10 4 The simulation results at T = 340fs are shown in the figure; (a) is the simulation result; (b) is a magnified view of the reflected wave; (c) is a magnified view of the transmitted wave.

[0045] Figure 8 n is the embodiment of the present invention e =10n c ≈10 28 m -3 B0~2×10 3 Simulation results at T = 100fs;

[0046] Figure 9 n is the embodiment of the present invention e =10n c ≈10 28 m -3 B0~2×10 3 Simulation results at T = 200 fs;

[0047] Figure 10 n is the embodiment of the present invention e =10n c ≈10 28 m -3 B0~2×10 3 Simulation results at T = 300 fs;

[0048] Figure 11 n is the embodiment of the present invention e =1.35n c ≈1.35×10 27 m -3 B0~7×10 3 Simulation results at T = 100fs;

[0049] Figure 12 n is the embodiment of the present invention e =1.35n c ≈1.35×10 27 m -3 B0~7×10 3 Simulation results at T, 240fs;

[0050] Figure 13 n is the embodiment of the present invention e =1.35n c ≈1.35×1027 m -3 B0~7×10 3 The simulation results at T = 300 fs are shown in the figure; (a) is the simulation result; (b) is a magnified view of the reflected wave; (c) is a magnified view of the transmitted wave.

[0051] Figure 14 This is a schematic diagram of the structure of a high-power laser pulse polarization state control system according to the present invention. Detailed Implementation

[0052] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0053] Example 1

[0054] like Figure 14 As shown, the present invention provides a high-power laser pulse polarization state control system, comprising a laser, a polarization controller, a processing device, and a central control unit.

[0055] The system comprises a laser for generating and outputting ultra-intense laser pulses; a polarization controller for receiving ultra-intense laser pulses emitted by the laser and rapidly adjusting the polarization direction of the ultra-intense laser pulses; a processing device for applying the ultra-intense laser pulses adjusted by the polarization controller to the processing material; and a central control unit electrically connecting the laser, polarization controller, and processing device to achieve synchronous control of the laser, polarization controller, and processing device.

[0056] To achieve polarization adjustment of ultra-intense laser pulses by the polarization controller, this invention introduces magnetized plasma, and the specific implementation process is as follows:

[0057] (1) Linearly polarized lasers can be decomposed into left-hand circularly polarized lasers and right-hand circularly polarized lasers.

[0058] (2) Left-handed and right-handed circularly polarized lasers have different dielectric constants in magnetized plasma, as shown below:

[0059]

[0060] Where, ε R ε is the dielectric constant of right-handed circularly polarized laser light; L ω is the dielectric constant of the left-hand circularly polarized laser; ω is the laser frequency. The plasma frequency is represented by e, and the electron charge is represented by m. e For electron mass; n e The plasma density; denoted as electron cyclotron frequency; B0 is the applied magnetic field strength; and c is the speed of light.

[0061] Therefore, left-handed circularly polarized laser and right-handed circularly polarized laser have different propagation properties in magnetized plasma. This difference in propagation properties makes it possible to control the polarization characteristics of laser pulses.

[0062] Example 2

[0063] Based on the different propagation properties of left-handed circularly polarized laser and right-handed circularly polarized laser in magnetized plasma, this example proposes a method for adjusting and controlling the polarization of ultra-intense laser pulses by a polarization controller and the simulation results.

[0064] 1. Control of the rotation of the polarization plane of linearly polarized laser (Faraday positive rotation).

[0065] When ε L > ε R > 0, the phase velocity of the right-handed wave is greater than that of the left-handed wave, and at this time, the polarization direction rotates positively; where B c is the critical magnetic field of electron cyclotron resonance; n c is the critical density of the plasma; the rotation angle is calculated as follows:

[0066]

[0067] Therefore, by controlling the plasma density and the background magnetic field strength, the rotation angle of the polarization plane can be regulated.

[0068] Set the PIC particle simulation parameters as: B0 = 2×10 3 T, n e = 0.1n c ≈ 10 26 m -3 , I0 = 1.24×10 17 W / cm 2 [[ID=CO]] c ≈ 10 4 T, n c ≈ 10 ) 27 m -3 ; the incident wave is a linearly polarized pulsed laser in the y direction. The simulation (two-dimensional) range is 120μm × 40μm. The plasma distribution range is 50μm < x < 70μm. The laser pulse is as follows:

[0069]

[0070] where I is the instantaneous laser intensity; w is the laser beam waist radius; y is the transverse spatial coordinate; t is the time variable; τ is the laser pulse width; let w = 10μm, τ = 30fs, and the laser is incident vertically from the x = 0 end as Figure 1 shown, and its simulation results are as Figure 2 As shown.

[0071] Figure 2 The pink field represents the electric field at 100 fs, when the laser pulse has not yet entered the plasma; the blue field represents the electric field at 240 fs, when the laser pulse is in the plasma; and the red field represents the electric field at 380 fs, when the laser pulse has passed through the plasma.

[0072] The rotation angle of the polarization plane after the laser pulse is emitted from the plasma. The theoretical value obtained from formula (3) is 74.83°, with an error of 4.3° and a relative error of about 5.75%. The error mainly comes from plasma diffusion.

[0073] 2. The linearly polarized laser is converted into a left-handed circularly polarized laser.

[0074] It can be seen from formula (1) that when When the denominator is approximately 0, the right-handed circularly polarized wave undergoes resonant absorption, and thus only the left-handed circularly polarized wave remains of the transmitted wave.

[0075] Set PIC simulation parameters: B0~10 4 T, and other parameters are the same as above; simulation results are as follows: Figure 3 As shown in (a), pink represents the electric field at 100 fs, when the laser pulse has not yet entered the plasma; blue represents the electric field at 240 fs, when the laser pulse is in the plasma; and red represents the electric field at 380 fs, when the laser pulse has left the plasma. Figure 3 In the diagram, (b) represents the electric field of the transmitted laser.

[0076] 3. Control of the polarization plane rotation of linearly polarized laser (Faraday inverse rotation).

[0077] when At that time, ε R >ε L >0, the phase velocity of the left-handed wave is greater than that of the right-handed wave, so the polarization direction rotates in the opposite direction. The rotation angle can still be expressed by formula (3).

[0078] Set PIC particle simulation parameters: B0~8×10 4 T, and other parameters are the same as above; simulation results are as follows: Figure 4 As shown, pink represents the electric field at 100 fs, when the laser pulse has not yet entered the plasma; blue represents the electric field at 240 fs, when the laser pulse is in the plasma; and red represents the electric field at 380 fs, when the laser pulse has left the plasma.

[0079] After the laser pulse is emitted from the plasma, its polarization plane rotates in the opposite direction, with the rotation angle being... The theoretical value obtained from formula (3) is -40.14°, with an error of 3.22° and a relative error of about 8%. The error mainly comes from plasma diffusion.

[0080] 4. Linearly polarized laser pulses are decomposed into left-handed and right-handed laser pulses (left-handed wave reflection, right-handed wave transmission).

[0081] when hour, It cannot propagate in the plasma and is therefore reflected at the plasma surface; the transmitted wave is only a right-handed wave.

[0082] Set PIC particle simulation parameters: n e =10n c ≈10 28 m -3 B0~5×10 4 T, and other parameters are the same as above; simulation results are as follows: Figure 5 The electric field shown is at 100 fs, before the laser pulse enters the plasma; as shown... Figure 6 The electric field at 240 fs is shown, at which point the right-handed wave has entered the plasma, and the left-handed wave is reflected at the plasma interface; as shown... Figure 7 The electric field at 340 fs is shown in (a) above, at which point both right-handed and left-handed spiral waves have left the plasma. Figure 7 (b) in the image is a magnified view of the reflected wave; Figure 7 (c) in the image is a magnified view of the transmitted wave.

[0083] 5. Electromagnetic wave shielding.

[0084] when At this time, neither left-handed nor right-handed spiral waves can propagate in the plasma and are reflected at the plasma surface.

[0085] Set PIC particle simulation parameters: n e =10n c ≈10 28 m -3 B0~2×10 3 T, the other parameters are the same as above;

[0086] Simulation results are as follows Figure 8 The electric field shown is at 100 fs, before the laser pulse enters the plasma; as shown... Figure 9 The electric field shown is at 200 fs, at which point the laser pulse is reflected at the plasma interface; as shown Figure 10 The electric field shown is at 300 fs, at which point the laser pulse has been reflected away from the plasma.

[0087] Depend on Figure 10It can be seen that the polarization plane of the reflected wave is deflected to a certain extent compared with the incident wave. The reason is that at the edge of the plasma, due to plasma diffusion, the boundary plasma density decreases, and the laser can enter a certain thickness of the plasma. During the process of the laser entering the plasma and leaving the plasma after being reflected by the reflecting surface, Faraday rotation occurs, so the polarization plane of the reflected wave is rotated.

[0088] 6. Linearly polarized laser pulses are decomposed into left-handed and right-handed laser pulses (right-handed wave is reflected, left-handed wave is transmitted).

[0089] when 1-B0 / B c <n e / n c <1+B0 / B c At that time, ε R <0, right-handed wave is reflected; ε L >0, the transmitted wave is a left-handed spiral wave.

[0090] Set PIC particle simulation parameters: n e =1.35n c ≈1.35×10 27 m -3 B0~7×10 3 T, and other parameters are the same as above; simulation results are as follows: Figure 11 The electric field shown is at 100 fs, before the laser pulse enters the plasma; as shown... Figure 12 The electric field at 240 fs is shown, at which point the right-handed wave is reflected at the interface, and the left-handed wave enters the plasma; as shown... Figure 13 The electric field at 300 fs is shown in (a) above, at which point both right-handed and left-handed spiral waves have left the plasma. Figure 13 (b) in the image is a magnified view of the reflected wave; Figure 13 (c) in the image is a magnified view of the transmitted wave.

[0091] Therefore, this invention employs the aforementioned high-intensity laser pulse polarization state control system and method. By introducing plasma as the control medium, it solves the problems of traditional optical components being easily damaged and exhibiting significant nonlinear effects under ultra-intense lasers, achieving a technological breakthrough in ultra-intense laser polarization control. It combines high tolerance, high precision, and adaptability, filling a technological gap in this field. It enables reliable control of the polarization state of high-intensity lasers and possesses efficient and stable polarization control capabilities. This provides a new solution for scenarios requiring high-intensity polarization control, such as laser processing, quantum information processing, and optical communication, improving the efficiency, precision, and stability of related applications.

[0092] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A high-power laser pulse polarization state control system, characterized in that, The system comprises a laser, a polarization controller, a processing device and a general controller. The laser is configured to generate and output laser pulses; the polarization controller is configured to receive the laser pulses emitted by the laser and adjust the polarization direction of the laser pulses; the processing device is configured to apply the laser pulses adjusted by the polarization controller to a processing material; and the general controller is electrically connected to the laser, the polarization controller and the processing device to realize synchronous control of the laser, the polarization controller and the processing device. In order to realize the polarization adjustment of the polarization controller on the ultrastrong laser pulse, a magnetized plasma is introduced, and the specific process is as follows: (1) the linearly polarized laser is decomposed into left circularly polarized laser and right circularly polarized laser; (2) the left circularly polarized laser and the right circularly polarized laser have different dielectric coefficients in the magnetized plasma, as shown below: (1)； (2)； wherein, is the dielectric coefficient for right circularly polarized laser light; is the dielectric coefficient for left circularly polarized laser light; is the laser frequency; is the plasma frequency; is the electronic charge; is the electronic mass; is the plasma density; is the electronic cyclotron frequency; is the background magnetic field strength; is the speed of light; Based on the above-mentioned strong laser pulse polarization state regulation system, a strong laser pulse polarization state regulation method is provided, which specifically comprises: (1) linear polarization laser polarization plane rotation control, i.e. Faraday forward rotation, as shown below: When , , , the right-handed wave phase velocity is greater than the left-handed wave phase velocity, at this time the polarization direction produces a positive rotation; wherein, is the electron cyclotron resonance critical magnetic field; is the plasma critical density; the rotation angle is calculated as follows: (3)； The polarization plane rotation angle is regulated by controlling the plasma density and the background magnetic field strength; The PIC particle simulation parameters are set as: , , , ; wherein, is a peak intensity of the laser; is a wavelength of the laser, , ; the incident wave is a y-direction linearly polarized pulsed laser; the two-dimensional simulation range is ; and the plasma distribution range is ; Laser pulse, as shown below: (4)； wherein, is the instantaneous laser intensity; is the laser beam waist radius; is the lateral spatial coordinate; is the time variable; is the laser pulse width; set , , the laser is vertically incident from the end; After the laser pulse exits the plasma, the angle of rotation of the polarization plane is given by equation (3) ; wherein and represent the components of the laser pulse electric field in the z and y directions, respectively. (2) linearly polarized laser is converted into left circularly polarized laser, as shown below: From equation (1), when the denominator is approximately equal to 0, i.e. the right circularly polarized wave is resonantly absorbed, and thus the transmitted wave is only the left circularly polarized wave; (3) linear polarization laser polarization plane rotation control, i.e. Faraday reverse rotation, as shown below: When , , , the left-handed wave phase velocity is greater than the right-handed wave phase velocity, so the polarization direction produces a reverse rotation; PIC particle simulation parameters are set: The rest of the parameters are the same as above; After the laser pulse exits from the plasma, the polarization plane reverses rotation, and the rotation angle is obtained from equation (3) ; (4) linearly polarized laser pulse is decomposed into left and right circularly polarized laser pulse, i.e. left circular wave reflection and right circular wave transmission, as shown below: When , , , the wave cannot propagate in the plasma and is reflected at the plasma surface, so that only right-handed waves are transmitted. (5) electromagnetic wave shielding, as shown below: When , both left-handed and right-handed waves cannot propagate in the plasma and are reflected at the plasma surface; (6) linearly polarized laser pulse is decomposed into left and right circularly polarized laser pulse, i.e. right circular wave reflection and left circular wave transmission, as shown below: When , , , the right-handed wave is reflected; , the transmitted wave is a left-handed wave.

Images