A device for generating impulse through Bessel laser beam reflection ablation

Abstract

This invention discloses a device for generating impulse through reflective ablation of a Bessel laser beam. The device includes: a target material, and a laser source, an aspherical lens, a first conical lens, a second conical lens, and a parabolic reflector arranged coaxially. The laser source emits a laser beam, which is collimated by the aspherical lens and then enters the first conical lens. The conical surfaces of the first and second conical lenses are positioned opposite each other. The first conical lens converts the collimated laser beam into a Bessel beam, and the second conical lens collimates and amplifies the Bessel beam into a ring-shaped Bessel beam. The parabolic reflector focuses the ring-shaped Bessel beam onto the target material, and the target surface ejects an ablation plume under the action of laser ablation, generating impulse. Applying this invention can effectively avoid the contamination problem of the plume ejection on optical devices and improve the reliability of the impulse generation process.

Description

Technical Field

[0001] This invention relates to the field of laser-matter interaction technology, and more particularly to a device for generating impulse through reflective ablation of a Bessel laser beam. Background Technology

[0002] Laser ablation impulse utilizes the mechanical effect generated by the interaction between laser and matter. When a laser irradiates the target surface, some of the laser energy is reflected, while the remaining laser energy is deposited on the target surface, causing the temperature in the irradiated area to rise. When the temperature of the working medium in the irradiated area reaches a critical value, the target melts and generates target vapor. The target vapor is further ionized to form a high-temperature, high-pressure plasma plume. The plume expands at high speed and leaves the target surface. According to the law of conservation of momentum, the working medium will gain recoil impulse. Due to its many advantages such as non-contact operation, high efficiency, and ease of control, laser ablation impulse technology has been widely applied in fields such as laser propulsion, laser processing, and laser-induced breakdown spectroscopy.

[0003] In laser ablation, the laser injection method is mainly divided into transmission and reflection ablation modes. In reflection mode, the ablation material and the laser injection path are on the same side. The laser passes through a focusing lens and is obliquely incident on the working surface, which reduces contamination of optical components to a certain extent and increases component lifespan. For reflection laser ablation mode, optical glass can also be added between the lens and the working medium to avoid contamination of the lens by material ejection during ablation. In transmission mode, after passing through the focusing lens, the laser passes through the transparent substrate and ablates the working medium coated on the other side of the substrate, thereby generating an ablation impulse. This avoids the problem of plasma plumes and particle clusters generated during the ablation process contaminating the focusing lens.

[0004] Currently, the following problems remain unsolved in the field of laser ablation technology:

[0005] 1) In the reflection ablation mode, the impulse generation method of oblique laser incidence requires increasing the incident angle between the laser and the normal of the working medium surface. As the incident laser increases, the irradiation spot of the laser on the working medium also increases, resulting in a decrease in laser irradiation power density and ultimately reducing the laser ablation impulse.

[0006] 2) In the reflection ablation mode, although installing optical glass can delay the contamination of optical components, it cannot fundamentally solve the contamination problem. As time goes by, although the optical glass can be replaced after it becomes contaminated, the transmittance of the optical glass will be affected by the contamination, making the ablation impulse unstable.

[0007] 3) In transmission mode, the substrate material does not participate in ablation. Since the laser needs to pass through the transparent substrate, the substrate reflects and absorbs the laser to a certain extent, which increases the laser energy loss.

[0008] Therefore, how to generate a high-efficiency laser ablation impulse while ensuring reduced laser loss and keeping optical components clean has become a technical problem that needs to be solved. Summary of the Invention

[0009] The purpose of this invention is to provide a device for generating impulse through reflective ablation of a Bessel laser beam, which improves the impulse generated by reflective ablation while ensuring the cleanliness of optical components.

[0010] To achieve the above objectives, the present invention provides the following technical solution:

[0011] According to one aspect of the present invention, a device for generating impulse through reflective ablation of a Bessel laser beam is provided. The device includes: a target material, and a laser source, an aspherical lens, a first conical lens, a second conical lens, and a parabolic reflector arranged coaxially. The laser source emits a laser beam, which is collimated by the aspherical lens and then enters the first conical lens. The conical surfaces of the first and second conical lenses are arranged opposite to each other. The first conical lens converts the collimated laser beam into a Bessel beam, and the second conical lens collimates and amplifies the Bessel beam into an annular Bessel beam. The parabolic reflector focuses the annular Bessel beam onto the surface of the target material, and the target material surface ejects an ablation plume under the action of laser ablation to generate impulse.

[0012] According to one embodiment of the present invention, the laser source is a continuous semiconductor laser or a pulsed semiconductor laser.

[0013] According to one embodiment of the present invention, the focal position of the aspherical lens coincides with the light exit position of the laser source.

[0014] According to one embodiment of the present invention, the first conical surface of the first conical lens and the second conical surface of the second conical lens are disposed adjacent to each other, and the first focal point of the first conical lens coincides with the second focal point of the second conical lens.

[0015] According to one embodiment of the present invention, the bottom angle of the first conical lens is the same as the bottom angle of the second conical lens.

[0016] According to one embodiment of the present invention, the parabolic reflector is formed by processing aluminum alloy material and then mirror polishing it, or by 3D printing aluminum alloy material and then mirror polishing it. According to the actual selected laser wavelength, the reflective surface is coated to form a high-reflectivity parabolic reflector.

[0017] According to one embodiment of the present invention, the target material is located at the focal point of the parabolic reflector.

[0018] According to one embodiment of the present invention, the generatrix equation of the parabolic reflector is (yr f ) 2=2px, the x-coordinate of the opening end of the parabolic reflector is the axial length L of the nozzle. n The vertical axis represents the nozzle opening radius R. n ,but:

[0019]

[0020] Where l is the distance from the focal point to the nozzle apex; p is the parameter of the generatrix equation of the nozzle inner wall; L is the distance from the focal point to the nozzle opening; r f Let r be the radius of the focusing ring, representing the distance between the ideal focal position and the axis of rotational symmetry. f When = 0, it indicates that the point is focused.

[0021] On the other hand, the present invention also provides a method for generating impulse through reflective ablation of a Bessel laser beam, comprising the following steps:

[0022] The laser is emitted using a laser, which is either a continuous laser or a pulsed Gaussian laser;

[0023] Use an aspherical lens to expand and collimate the laser beam;

[0024] The collimated laser beam is converted into a Bessel beam using a first conical lens;

[0025] The Bessel beam is magnified and collimated into a ring-shaped Bessel beam using a second cone lens.

[0026] A parabolic reflector is used to converge a ring-shaped Bessel beam from all sides onto the surface of the target material for ablation. Under the action of laser ablation, the surface of the target material ejects an ablation plume to generate momentum.

[0027] On the other hand, the present invention also provides an external spacecraft, including the aforementioned device for generating impulse through reflective ablation of a Bessel laser beam, wherein the device for generating impulse through reflective ablation of a Bessel laser beam is disposed outside the external spacecraft and is used to generate impulse to propel the external movement of the external spacecraft.

[0028] The device for generating impulse through Bessel laser beam reflection ablation provided by this invention has the following advantages compared with the prior art:

[0029] 1. By using a parabolic reflector to converge the annular Bessel beam from all sides onto the end face of the target material for ablation, the contamination problem caused by the plume jet to the optical device can be effectively avoided, and the reliability of the impulse generation process can be improved.

[0030] 2. Compared with the traditional reflective laser ablation process, the optical path design of the Bessel laser beam reflective ablation device for generating impulse in this invention can generate a smaller, more uniform, and neatly edged Bessel spot on the target surface, thereby obtaining higher laser power density and more consistent light energy distribution, and achieving better impulse generation performance.

[0031] 3. Converting the laser into a Bezier spot improves the repeatability and stability of the impulse generated by ablation, resulting in more uniform target ablation and a smoother, more consistent ablation surface. Attached Figure Description

[0032] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this invention, illustrate exemplary embodiments of the invention and are used to explain the invention, but do not constitute an undue limitation of the invention. In the drawings:

[0033] Figure 1 This is a schematic diagram of a device for generating impulse through reflective ablation of a Bessel laser beam according to an exemplary embodiment of the present invention.

[0034] Figure 2 This is a schematic diagram of a first conical lens converting a laser beam into a Bessel beam according to an exemplary embodiment of the present invention.

[0035] Figure 3 This is a schematic diagram of a parabolic reflector according to an exemplary embodiment of the present invention. Detailed Implementation

[0036] To facilitate a clear description of the technical solutions in the embodiments of the present invention, the terms "first" and "second" are used to distinguish identical or similar items with essentially the same function and effect. For example, the first threshold and the second threshold are merely used to distinguish different thresholds and do not limit their order. Those skilled in the art will understand that the terms "first" and "second" do not limit the quantity or execution order, and that the terms "first" and "second" are not necessarily different.

[0037] It should be noted that in this invention, the terms "exemplary" or "for example" are used to indicate examples, illustrations, or descriptions. Any embodiment or design described as "exemplary" or "for example" in this invention should not be construed as being more preferred or advantageous than other embodiments or designs. Specifically, the use of terms such as "exemplary" or "for example" is intended to present the relevant concepts in a concrete manner.

[0038] In this invention, "at least one" refers to one or more, and "more than one" refers to two or more. "And / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A alone, A and B simultaneously, or B alone, where A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects are in an "or" relationship. "At least one" or similar expressions refer to any combination of these items, including any combination of singular or plural items. For example, "at least one of a, b, or c" can represent: a, b, c, a combination of a and b, a combination of a and c, a combination of b and c, or a, b, and c, where a, b, and c can be single or multiple.

[0039] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0040] like Figure 1 The diagram shows a schematic of a device for generating impulse through reflective ablation using a Bessel laser beam. The device includes: a laser source 1, an aspherical lens 2, a first conical lens 3, a second conical lens 4, a target material 5, and a parabolic reflector 6.

[0041] Laser source 1 emits a laser beam, which is collimated by aspherical lens 2 and then enters first conical lens 3. The conical surfaces of first conical lens 3 and second conical lens 4 are positioned opposite each other, and together they amplify the collimated laser beam into a ring-collimated laser beam. The ring-collimated laser beam enters parabolic reflector 6, which focuses the ring-collimated laser beam onto the surface of target material 5. Under the action of laser ablation, the surface of target material 5 ejects an ablation plume 7, and the ejection of the plume causes the target material 5 to gain a recoil impulse. Laser source 1, aspherical lens 2, first conical lens 3, second conical lens 4, and parabolic reflector 6 share a common optical axis.

[0042] Laser source 1 is a semiconductor laser. The laser operates in two modes: continuous emission and pulsed emission. In pulsed mode, the laser pulse width is adjustable. Pulsed laser ablation generates impulse, while continuous laser ablation generates an accumulation of impulse over time, i.e., thrust.

[0043] Aspherical lens 2 is used to collimate the laser emitted from laser source 1. The focal point of aspherical lens 2 coincides with the exit port of laser source 1. The collimated emitted laser is then fed into the first conical lens 3. Aspherical lens 2 does not introduce spherical aberration during focusing or collimation. For monochromatic light sources, spherical aberration is often a factor limiting the diffraction-limited performance of a single spherical lens during focusing or collimation. Therefore, an aspherical lens is chosen to collimate the emitted laser.

[0044] The first conical lens 3 is used to convert the collimated laser into a Bessel beam, wherein the Bessel beam is a ring beam.

[0045] like Figure 2 As shown, from the cross-section of the annular beam, it consists of a ring-shaped part surrounded by two inner and outer circles. The Bessel beam has the characteristics of no diffraction and self-restoring.

[0046] The second conical lens 4 is used to collimate the Bessel beam. If the Bessel beam is not collimated, the installation position of the parabolic mirror 6 will be limited by the beam divergence angle. After the Bessel beam is collimated by the second conical lens 4, the distance between the second conical lens 4 and the parabolic mirror can be adjusted according to actual needs.

[0047] The parabolic reflector 6 is used to focus the collimated Bessel beam onto the surface of the working target 5 from all sides in an oblique incidence manner for ablation, forming an ablation plume 7 jet, thereby generating an ablation impulse.

[0048] To facilitate the fabrication of the parabolic reflector 6, a complete parabolic reflector is first designed and defined. The parabolic reflector is formed by machining aluminum alloy and then mirror polishing it, or by 3D printing aluminum alloy and then mirror polishing it. Based on the selected laser wavelength, a high-reflectivity parabolic reflector is formed by coating the reflective surface.

[0049] like Figure 3 As shown, after processing, based on the outer and inner diameters of the collimated Bessel beam, the complete parabolic mirror is cut using precision machining processes such as wire cutting or 3D printing technology to retain a parabolic mirror between radii W1 and W2, where radius W1 is larger than the outer diameter of the Bessel ring beam and radius W2 is smaller than the inner diameter of the Bessel ring beam.

[0050] Assume the equation of the generatrix of the parabolic mirror is (yr f ) 2 =2px, N is the opening end of the nozzle, if the x-coordinate of point N is defined as the axial length L of the nozzle. n The vertical axis represents the nozzle opening radius R. n ,but:

[0051]

[0052] Where l is the distance from the focus to the nozzle apex, p is the parameter of the generatrix equation of the nozzle inner wall, L is the distance from the focus to the nozzle opening, and r f The radius of the focusing ring, representing the distance between the ideal focal position and the rotational symmetry axis, characterizes the shape of the energy deposition region. f=0 indicates point focusing. W1 and W2 represent the distances from the two ends of the parabolic mirror to the axis of rotational symmetry.

[0053] Figure 1 The device for generating impulse through reflective ablation of the Bessel laser beam shown works as follows: The laser source 1 emits a laser beam, which is collimated by the aspherical lens 2 and then enters the first conical lens 3. The generated Bessel beam is collimated by the second conical lens 4 and then introduced onto the parabolic reflector 6. Subsequently, the collimated Bessel beam is focused from all sides onto the surface of the working target 5 in an oblique incidence manner, and the target surface is subjected to laser ablation. The laser ablation generates a plume jet 7, which in turn generates impulse.

[0054] based on Figure 1 The apparatus shown illustrates a method for generating impulse through reflective ablation using a Bessel laser beam, comprising the following steps:

[0055] Step S1: Use a laser to emit laser light, wherein the laser light is a continuous laser light or a pulsed Gaussian laser light;

[0056] Step S2: Use an aspherical lens to expand and collimate the laser beam;

[0057] Step S3: Use the first cone lens to convert the collimated laser into a Bessel beam;

[0058] Step S4: Collimate the Bessel beam using the second cone lens;

[0059] Step S5: Use a parabolic reflector to converge the annular Bessel beam from all sides onto the target surface for ablation, thereby generating a laser ablation impulse.

[0060] Example 1:

[0061] A 1064nm Gaussian continuous laser is generated using a laser as the laser source 1.

[0062] A Gaussian continuous laser was collimated using an aspherical lens 2 with a focal length of 10.5 mm and a diameter of 12 mm.

[0063] A first conical lens 3 with a diameter of 12.7 mm and a base angle of 20° is used to convert the aligned Gaussian continuous beam into a Bessel beam. The width of the Bessel beam's ring remains constant throughout its propagation. Although both the inner and outer diameters of the Bessel beam increase with the transmission distance, the difference between the inner and outer diameters remains constant. As can be seen from the Bessel beam diagram, the width is constant, and the ring width is equal to the radius of the Gaussian continuous laser beam when it enters the first conical lens 3.

[0064] The Bessel beam is collimated using a second conical lens 4 with a diameter of 50.8 mm and a base angle of 20°. The collimated Bessel beam then enters the parabolic reflector 6, which is formed by processing aluminum alloy material and then polishing it to a mirror finish.

[0065] When parameter rf = 0, the focusing type of the parabolic reflector 6 is point focusing. After the Bessel beam entering the parabolic reflector 6 is reflected, it converges from all sides to the focal point of the parabolic reflector 6. This focal point is located on the surface of the working fluid target. The laser energy is deposited on the surface of the working fluid target to generate an ablation plume. The plume is rapidly ejected in a direction perpendicular to the surface of the target, avoiding contamination of the optical elements by the ablation plume. According to the conservation of momentum, a recoil impulse will be generated in the opposite direction of the ablation plume ejection.

[0066] Because it can generate recoil impulse, the Bessel laser beam reflective ablation device of the present invention can be used as a propulsion device for spacecraft in outer space, using the generated recoil impulse as propulsion to move the spacecraft. The present invention also provides an outer spacecraft including the aforementioned Bessel laser beam reflective ablation device, which is disposed outside the outer spacecraft and used to generate impulse to propel the outer spacecraft.

[0067] This invention discloses a device for generating impulse through reflective ablation using a Bessel laser beam. It utilizes first and second conical lenses to convert the laser emitted from a laser source into a ring-shaped Bessel beam. A parabolic reflector focuses the Bessel beam at an oblique incidence onto the surface of a working target material, generating an ablation impulse. This effectively avoids surface contamination of optical components caused by ablation plume jets. Because the Bessel beam has no diffraction characteristics, the laser focused on the working target surface produces a smaller, more uniform, and neatly edged ablation spot, resulting in higher laser power density and a more consistent light energy distribution. This leads to better repeatability and stability of the ablation impulse, more uniform target ablation, and a smoother, more uniform ablation surface.

[0068] Although the invention has been described herein in conjunction with various embodiments, those skilled in the art will understand and implement other variations of the disclosed embodiments by reviewing the accompanying drawings, disclosure, and other materials. In this specification, the word "comprising" does not exclude other components or steps, and "a" or "an" does not exclude multiple components. A single processor or other unit can implement several of the functions listed in the specification. While certain measures are described in different embodiments, this does not mean that these measures cannot be combined to produce good results.

[0069] Although the invention has been described in conjunction with specific features and embodiments, it is obvious that various modifications and combinations can be made therein without departing from the spirit and scope of the invention. Accordingly, this specification and drawings are merely illustrative of the invention and are considered to cover any and all modifications, variations, combinations, or equivalents within the scope of the invention. Clearly, those skilled in the art can make various alterations and modifications to the invention without departing from its spirit and scope. Thus, if such modifications and modifications fall within the scope of the invention and its equivalents, the invention is also intended to include such modifications and modifications.

Claims

1. A device for generating impulse through Bessel laser beam reflection ablation, characterized in that, The device includes: a target material, and a laser source, an aspherical lens, a first conical lens, a second conical lens, and a parabolic reflector arranged coaxially; A laser source emits a laser beam, which is collimated by an aspherical lens and then enters a first conical lens. The conical surfaces of the first and second conical lenses are positioned opposite each other. The first conical lens converts the collimated laser beam into a Bessel beam, and the second conical lens collimates and amplifies the Bessel beam into a ring-shaped Bessel beam. The parabolic reflector focuses the annular Bessel beam onto the target surface, and the target surface generates an ablation plume under the action of laser ablation.

2. The apparatus for generating impulse through Bessel laser beam reflection ablation according to claim 1, characterized in that, The laser source is either a continuous semiconductor laser or a pulsed semiconductor laser.

3. The apparatus for generating impulse through Bessel laser beam reflection ablation according to claim 1, characterized in that, The focal position of the aspherical lens coincides with the light outlet position of the laser source.

4. The apparatus for generating impulse through Bessel laser beam reflection ablation according to claim 1, characterized in that, The first conical surface of the first conical lens is adjacent to the second conical surface of the second conical lens, and the first focal point of the first conical lens coincides with the second focal point of the second conical lens.

5. The apparatus for generating impulse through Bessel laser beam reflection ablation according to claim 4, characterized in that, The bottom angle of the first conical lens is the same as that of the second conical lens.

6. The apparatus for generating impulse through Bessel laser beam reflection ablation according to claim 1, characterized in that, The parabolic reflector is formed by processing aluminum alloy material and then polishing it to a mirror finish, or by 3D printing aluminum alloy material and then polishing it to a mirror finish. Depending on the actual selected laser wavelength, a reflective surface coating is applied to form a high-reflectivity parabolic reflector.

7. The apparatus for generating impulse through Bessel laser beam reflection ablation according to claim 1, characterized in that, The target material is located at the focal point of the parabolic reflector.

8. The apparatus for generating impulse through Bessel laser beam reflection ablation according to claim 1, characterized in that, The generatrix equation of the parabolic mirror is: The x-coordinate of the opening end of the parabolic reflector is the axial length of the nozzle. L n The vertical axis represents the nozzle opening radius. R n ,but: in, l The distance from the focal point to the nozzle apex; p These are the parameters of the generatrix equation for the inner wall of the nozzle; L The distance from the focal point to the nozzle opening; r f The radius of the focusing ring refers to the distance between the ideal focal position and the axis of rotational symmetry. r f When = 0, it indicates that the point is focused.

9. A method for generating impulse through Bessel laser beam reflection ablation based on the device of claim 1, characterized in that, Includes the following steps: The laser is emitted using a laser, which is either a continuous laser or a pulsed Gaussian laser; Use an aspherical lens to expand and collimate the laser beam; The collimated laser beam is converted into a Bessel beam using a first conical lens; The Bessel beam is magnified and collimated into a ring-shaped Bessel beam using a second cone lens. A parabolic reflector is used to converge a ring-shaped Bessel beam from all sides onto the surface of the target material for ablation. Under the action of laser ablation, the surface of the target material ejects an ablation plume to generate momentum.

10. An external spacecraft, characterized in that, The device includes any one of claims 1 to 8 for generating impulse through reflective ablation of a Bessel laser beam, wherein the device is disposed outside the external spacecraft and is used to generate impulse to propel the external spacecraft.

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