A long-distance, high-efficiency composite laser damage method

Abstract

The present invention provides a long-distance, high-efficiency composite laser damage method, comprising: firstly, realizing high-power long-distance transmission of ultrafast laser, specifically, spatially focusing high-energy ultrafast laser to form kilometer-long optical filaments, which can maintain a constant high power density (10 13 ‑10 15 W / cm 2 ), completing the initial damage to the target surface; simultaneously, the high-energy continuous laser is transmitted over the same distance and acts on the same location on the target, achieving a combined ultrafast laser / continuous laser effect, thereby achieving long-distance, efficient damage to the target. This invention utilizes the spatial filamentation and transmission capabilities of high-energy ultrafast lasers to achieve initial damage to transparent, highly reflective targets after transmission distances of up to 100 kilometers, forming defects and significantly improving the material's absorption of high-energy continuous laser light. Furthermore, the shock wave generated by the simultaneous ultrafast laser filamentation enhances the removal of molten material, resulting in effective damage to the target under the continuous action of the composite laser.

Description

Technical Field

[0001] The present invention relates to the field of laser technology applications, and in particular to a long-distance, high-efficiency composite laser damage method. Background Art

[0002] High-energy lasers have the advantages of concentrated energy, fast transmission speed, fast fire response, high hit accuracy, long effective range, strong anti-interference ability, multiple reuse and good economy, and are showing a rapid development trend.

[0003] Existing high-energy laser damage is mainly based on high-energy continuous laser. After long-distance transmission (tens of kilometers), the laser diverges and the power at the target is significantly reduced. The laser power density acting on the target material is about 1000W / cm 2 The laser ablation efficiency is very low, requiring continuous irradiation time of 1-10 seconds to effectively damage the target. Furthermore, it is difficult to effectively damage transparent, hard-brittle materials (such as sapphire windows and armored ceramics) and highly reflective alloys (such as titanium alloys and aluminum alloys). Improving the damage capability by significantly increasing laser power and other indicators will undoubtedly increase the difficulty and cost of high-energy laser development. Therefore, how to control the efficiency of high-energy laser ablation to achieve long-range, efficient damage to transparent, highly reflective target materials has become a problem and challenge that needs to be solved urgently.

[0004] Many studies have shown that the assistance of short-pulse lasers can greatly reduce the ablation threshold of the target material under the action of continuous lasers or long-pulse lasers (by about one order of magnitude). Composite laser ablation technology can achieve high damage efficiency while reducing the power requirement of high-energy lasers - this can provide a new entry point for the development of existing high-energy laser ablation technology. In this regard, the authorized patent (CN 221238252 U) combines continuous lasers and pulsed lasers to ablate the projectile. First, the surface of the unexploded bomb is irradiated by a continuous laser to heat the surface of the projectile, and then the surface of the projectile is ablated by a pulsed laser. However, the existing composite damage methods all directly use focusing to achieve material ablation within a short distance. For high-energy laser damage at long distances (on the order of tens of kilometers), considering the influence of atmospheric attenuation, turbulence, thermal bloom, and nonlinear effects such as stimulated Raman scattering and atmospheric breakdown, the power will drop significantly and it will be difficult to focus the target to achieve the required power density (>10 7 W / cm 2 Some composite laser methods can achieve high peak power density at short focal lengths, but over long distances, the power density drops to one percent or even one thousandth, making it difficult to create defects on the material surface or stimulate plasma shock waves.

[0005] In terms of transmission, femtosecond laser spatial filamentation has significant advantages. When high-power laser is transmitted in the air, the plasma channel generated by the ionized medium is usually called "light filament". This process is also called filamentation, and the phenomenon that the light intensity in the filament remains constant is called the light intensity clamping effect (about 10 14 W / cm 2 Therefore, femtosecond laser spatial filamentation possesses the ability to transmit data over long distances, providing a new approach for high-efficiency damage to transparent media. By leveraging the power density retention characteristics of ultrafast laser spatial filamentation during long-distance transmission, and assisting high-energy continuous lasers in target damage, the challenge of long-distance laser damage can be fully addressed. Summary of the Invention

[0006] Aiming at the problem of low damage efficiency ratio in the existing high-energy continuous laser long-distance transmission, a new method of ultrafast laser spatial filamentation-assisted high-energy continuous laser long-distance transmission damage is proposed.

[0007] By focusing high-energy ultrafast lasers in space to form optical filaments, the length of the optical filaments can be controlled to tens of kilometers, and the diameter of the optical filaments can be in the order of millimeters to centimeters. Due to the light intensity clamping effect inside the optical filaments, the power density can be stabilized at 10 13 -10 15 W / cm 2 Therefore, ultrafast laser spatial filamentation can achieve high-power continuous long-distance transmission, thereby achieving indiscriminate damage to transparent and highly reflective target materials.

[0008] Ultrafast laser spatial filamentation simultaneously transmits over long distances and assists high-energy continuous lasers in achieving spatially synchronized focusing, creating a combined ultrafast / continuous laser / continuous laser effect. Transparent and highly reflective targets are not damaged by a single continuous laser due to their low absorption. However, with the assistance of ultrafast laser filamentation, the high peak power density burns the target surface, creating defects that significantly reduce the absorption of these materials. Therefore, ultrafast laser spatial filamentation, coupled with continuous lasers, can achieve surface ablation of these targets.

[0009] After defect absorption is improved, ultrafast laser spatial filamentation and continuous laser spatial focusing will effectively melt the target material. The shock wave excited by the femtosecond laser spatial filamentation will enhance the removal of molten material, thus effectively destroying the target material under continuous action.

[0010] The present invention provides a long-distance, high-efficiency composite laser damage method, comprising the following steps:

[0011] Step 1: Use spatial focusing or direct transmission of high-energy ultrafast lasers to form kilometer-long filaments. The light intensity clamping characteristics of the filaments ensure that the filaments can maintain a constant high power density during long-distance transmission, thereby achieving initial damage to the surface of the distant target.

[0012] Step 2: The high-energy continuous laser is transmitted over the same distance and then applied to the same location on the target. The ultrafast laser creates defects on the target surface, significantly increasing the material's absorption of the high-energy continuous laser. Furthermore, the shock waves generated by spatial filamentation enhance the removal of molten material, effectively damaging the target through the combined action of the ultrafast laser and continuous laser.

[0013] Furthermore, the ultrafast laser is a picosecond laser or a femtosecond laser.

[0014] Furthermore, the target material is sapphire, alumina ceramics, titanium alloy, etc.

[0015] Furthermore, the wavelength of the ultrafast continuous laser is in the range of 266-2000 nm.

[0016] Furthermore, the repetition rate of high-energy ultrafast lasers is 1kHz-10 MHz.

[0017] Furthermore, the diameter of the filament formed by high-energy ultrafast laser is from hundreds of microns to several centimeters, and the power density is 10 13 -10 15 W / cm 2 .

[0018] Furthermore, the continuous laser diameter is 1-20cm, the continuous laser power is in the 10,000-10 million watt level, and the power density acting on the target after transmission is 100W / cm 2 -10000 W / cm 2 .

[0019] Furthermore, the transmission distance of the composite laser can reach up to 100 kilometers.

[0020] Furthermore, the transmission direction of the composite laser is adjusted by a collimator and a reflector, and coaxial transmission or transmission at a certain angle is achieved to act on the same position.

[0021] Furthermore, high-energy ultrafast laser can be output in burst mode to extend the filament length and enhance the filament stability.

[0022] Beneficial effects

[0023] In general, the above technical solutions conceived by the present invention have the following technical advantages compared with the existing technology:

[0024] 1. Existing long-distance high-energy laser damage methods primarily rely on continuous laser action. This can lead to divergence and power attenuation after long-distance transmission, resulting in insufficient power density to damage transparent and highly reflective target materials. However, the power clamping effect of ultrafast laser spatial filamentation enables high-power laser transmission over a range of tens of kilometers, creating defects by ablation on the surface of transparent and highly reflective targets. These defects significantly enhance laser absorption under subsequent composite laser action, thereby increasing damage efficiency.

[0025] 2. The long-distance, high-efficiency composite laser damage method proposed in this invention solves the problem of single continuous laser damage to transparent and highly reflective targets. While significantly improving damage efficiency compared to single ultrafast laser damage, the long-distance, high-efficiency composite laser damage method addresses this issue. While ultrafast laser focused filamentation offers high peak power density, its damage efficiency is significantly limited by shielding from the excited plasma, and the injected laser energy differs significantly from the continuous laser energy in composite lasers. Consequently, the damage efficiency achievable with single ultrafast laser spatial filamentation over long distances is far less than that achieved with composite laser damage.

[0026] 3. In addition, the combination of femtosecond laser spatial filamentation and continuous laser can achieve penetrating damage to the target material in a shorter time. Existing high-energy continuous laser damage methods require 1-10 seconds to achieve penetrating damage to the target material. However, with the assistance of femtosecond laser spatial filamentation, continuous laser with the same parameters can achieve penetrating damage to the target material in 50ms.

[0027] The present invention proposes a new method of using ultrafast laser space filamentation to assist high-energy continuous laser long-distance transmission for damage. On the one hand, it fully utilizes the long-distance high-peak power transmission performance of ultrafast laser space filamentation, and on the other hand, it utilizes the high-energy injection characteristics of high-energy continuous laser to achieve a composite effect of ultrafast + continuous >> ultrafast or continuous, thereby realizing long-distance, high-efficiency laser damage effects on various types of materials such as transparent and highly reflective materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a system diagram of the long-distance, high-efficiency composite laser damage method provided by the present invention.

[0029] [Description of Reference Numerals]

[0030] 1-Control system; 2-Continuous laser; 3-Ultrafast laser; 4-Filament; 5-Target. DETAILED DESCRIPTION

[0031] In order to make the technical problems, technical solutions and advantages to be solved by the present invention clearer, the following will be described in detail with reference to the accompanying drawings and specific embodiments. It should be noted that the description of these embodiments is used to help understand the present invention, but does not constitute a limitation of the present invention.

[0032] Example 1:

[0033] A 20mJ, 1kHz, 800nm ​​high-energy femtosecond laser is transmitted through a telescope system for 3km in an atmospheric environment, and then spatially focused to achieve a filament with a diameter of 1cm and a length of 1km. At the same time, a 10kW continuous laser and a 1064nm high-energy continuous laser are collimated and output with a spot diameter of 3cm, which is transmitted coaxially with the femtosecond laser. 3mm thick sapphire, alumina ceramics, titanium alloy, etc. are placed at 3.2km, 3.4km, and 3.6km away from the composite laser system to test the composite laser damage effect. A single continuous laser will not cause any damage to the target material due to its low power density and low absorption of laser by the target material. A single femtosecond laser can damage multiple types of target materials for 1s, and can only achieve defects of 50-200μm in depth. However, under the same parameters of femtosecond and continuous laser composite damage, a through hole with a diameter of about 2cm can be ablated on multiple types of target materials within 1s.

[0034] Example 2:

[0035] A femtosecond continuous composite laser damage system was constructed, with high-energy femtosecond laser parameters of 25mJ, 500kHz, and 515nm, operating in burst mode (25 sub-pulses, each with 1mJ energy); and high-energy continuous laser parameters of 500kW and 1064nm. Two laser beams were coaxially transmitted using an optical lens system, forming filaments in the atmospheric environment. A 6mm thick sapphire target was placed 25km from the damage system, and the composite laser applied to the sapphire to cause it to explode.

[0036] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A long-distance, high-efficiency composite laser damage method, characterized in that: include: Step 1: Kilometer-long filaments are formed by spatially focusing or directly transmitting a high-energy ultrafast laser with a repetition rate of 1kHz-10 MHz. The high-energy ultrafast laser is output in burst mode to extend the filament length and enhance the filament stability. The light intensity clamping property of the filament ensures that the filament maintains a constant high power density during long-distance transmission, achieving initial damage to the surface of the distant target. Step 2: The diameter is 1-20cm, the power is 10,000W to 10,000W, and the power density to the target is 100W / cm 2 -10000W / cm 2 The high-energy continuous laser is transmitted for the same distance and then acts on the same position of the target. The ultrafast laser forms defects on the target surface, which can significantly improve the material's absorption of the high-energy continuous laser. The shock wave excited by the spatial filamentation will enhance the removal of the molten material, thereby achieving effective damage to the target through the combined action of the ultrafast laser / continuous laser. The transmission direction of the composite laser is adjusted by the collimator and reflector to achieve a certain angle of transmission and then act on the same position.

2. The long-distance, high-efficiency composite laser damage method according to claim 1 is characterized in that: The ultrafast laser is a picosecond laser or a femtosecond laser.

3. The long-distance, high-efficiency composite laser damage method according to claim 1, characterized in that: The target material is sapphire, alumina ceramic or titanium alloy.

4. The long-distance, high-efficiency composite laser damage method according to claim 1, characterized in that: The wavelength of the ultrafast continuous laser is in the range of 266-2000 nm.

5. The long-distance, high-efficiency composite laser damage method according to claim 1, characterized in that: The diameter of the filament formed by high-energy ultrafast laser is from hundreds of microns to several centimeters, and the power density is 10 13 -10 15 W / cm 2 .

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