Bessel laser beam reflection type ablation impulse generation device

Abstract

The invention discloses a device for generating impulse through Bessel laser beam reflection type ablation. The device comprises a target material, a laser light source, an aspherical lens, a first conical lens, a second conical lens and a parabolic reflector, wherein the laser light source, the aspherical lens, the first conical lens, the second conical lens and the parabolic reflector share the same optical axis. The laser light source emits a laser beam, the laser beam enters the first conical lens after being collimated by the aspherical lens, the conical surface of the first conical lens and the conical surface of the second conical lens are oppositely arranged, the first conical lens converts collimated laser 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 to a target material, and the surface of the target material is jetted out of an ablation plume under the action of laser ablation to generate impulse. According to the invention, the pollution problem of plume injection to an optical device can be effectively avoided, and the reliability of the impulse generation process is improved.

Description

Technical Field

[0001] The invention relates to the technical field of interaction between laser and matter, and in particular to a device for generating impulse by reflection ablation of a Bessel laser beam. Background Art

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

[0003] During the laser ablation process, the laser injection method is mainly divided into transmission and reflection ablation modes. In the reflection mode, the ablation material and the laser injection optical path are on the same side. The laser passes through the focusing lens and is incident obliquely on the surface of the working fluid, which reduces the contamination of the optical components to a certain extent and increases the service life of the components. For the reflection laser ablation mode, optical glass can also be added between the lens and the working fluid to avoid the contamination of the lens by the material ejected by the ablation. In the transmission mode, the laser passes through the focusing lens and then passes through the transparent substrate to ablate the working fluid smeared on the other side of the substrate, thereby generating an ablation impulse, avoiding the problem of plasma plumes and particle clusters ejected during the ablation process and contaminating the focusing lens.

[0004] At present, there are still several unresolved issues in the field of laser ablation technology:

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

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

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

[0008] Therefore, how to generate efficient laser ablation impulse while ensuring reducing laser loss and keeping optical components clean becomes a technical problem that needs to be solved. Summary of the invention

[0009] The object of the present invention is to provide a device for generating impulse by reflective ablation of a Bessel laser beam, which can improve the impulse generated by reflective ablation and ensure the cleanliness of optical elements.

[0010] To achieve the above object, the present invention provides the following technical solutions:

[0011] According to one aspect of the present invention, there is provided a device for generating impulse by reflective ablation of a Bessel laser beam, the device comprising: a target material, and a laser light source, an aspheric lens, a first conical lens, a second conical lens, and a parabolic reflector arranged on a coaxial axis; the laser light source emits a laser beam, the laser beam enters the first conical lens after being collimated by the aspheric lens, the conical surfaces of the first conical lens and the second conical lens 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 surface of the target material ejects an ablation plume under the action of laser ablation to generate impulse.

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

[0013] According to an embodiment of the present invention, the focal position of the aspheric lens coincides with the light outlet position of the laser light source.

[0014] According to an embodiment of the present invention, the first conical surface of the first conical lens is arranged adjacent to the second conical surface of the second conical lens, and the first focal position of the first conical lens coincides with the second focal position of the second conical lens.

[0015] According to an embodiment of the present invention, a base angle of the first axicon is the same as a base angle of the second axicon.

[0016] According to one embodiment of the present invention, the parabolic reflector is formed by processing aluminum alloy material and then mirror polishing, or by 3D printing aluminum alloy material and then mirror polishing. 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 position of a parabolic reflector.

[0018] According to one embodiment of the present invention, the generatrix equation of the parabolic reflector is (yr f ) 2=2px, the horizontal coordinate of the open end of the parabolic reflector is the axial length L of the nozzle n , the longitudinal coordinate is the nozzle opening radius R n ,but:

[0019]

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

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

[0022] Using a laser to emit laser, the laser is a continuous laser or a pulsed Gaussian laser;

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

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

[0025] A second axicon is used to amplify and collimate the Bessel beam into a circular Bessel beam;

[0026] A parabolic reflector is used to converge the annular Bessel beam from all sides to the target surface for ablation. Under the action of laser ablation, the target surface ejects an ablation plume to generate impulse.

[0027] On the other hand, the present invention also provides an external space vehicle, including the device for generating impulse by Bessel laser beam reflection ablation, wherein the device for generating impulse by Bessel laser beam reflection ablation is arranged outside the external space vehicle and is used to generate impulse to drive the external movement of the external space vehicle.

[0028] Compared with the prior art, the device for generating impulse by Bessel laser beam reflection ablation provided by the present invention has the following beneficial effects:

[0029] 1. Using a parabolic reflector to converge the annular Bessel beam from all sides to the end face of the target for ablation can effectively avoid the pollution problem of the optical device caused by the plume injection and improve the reliability of the impulse generation process;

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

[0031] 3. Convert the laser into a Bessel spot, so that the impulse generated by ablation has better repeatability and stability, the target material is ablated more evenly, and the ablation surface tends to be smoother and more consistent. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings:

[0033] Figure 1 Schematic diagram of a device for generating impulse by Bessel laser beam reflection ablation according to an exemplary embodiment of the present invention.

[0034] Figure 2 FIG. 1 is a schematic diagram of converting a laser beam into a Bessel beam using a first axicon according to an exemplary embodiment of the present invention.

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

[0036] In order to clearly describe the technical solutions of the embodiments of the present invention, in the embodiments of the present invention, words such as "first" and "second" are used to distinguish the same items or similar items with basically the same functions and effects. For example, the first threshold and the second threshold are only used to distinguish different thresholds, and their order is not limited. Those skilled in the art can understand that words such as "first" and "second" do not limit the quantity and execution order, and words such as "first" and "second" do not necessarily limit them to be different.

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

[0038] In the present invention, "at least one" means one or more, and "plurality" means two or more. "And / or" describes the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone, where A and B can be singular or plural. The character " / " generally indicates that the associated objects before and after are in an "or" relationship. The following at least one item (items) or similar expressions thereof refer to any combination of these items, including any combination of single items (items) or plural items (items). For example, at least one item (items) of a, b or c can mean: a, b, c, the combination of a and b, the combination of a and c, the combination of b and c, or the combination of a, b and c, where a, b, c can be single or multiple.

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

[0040] like Figure 1 As shown, a schematic diagram of a device for generating impulse by reflective ablation of a Bessel laser beam is given. The device comprises: a laser light source 1, an aspheric lens 2, a first axicon 3, a second axicon 4, a target 5, and a parabolic reflector 6.

[0041] The laser light source 1 emits a laser beam, which enters the first cone lens 3 after being collimated by the aspheric lens 2. The conical surfaces of the first cone lens 3 and the second cone lens 4 are arranged opposite to each other, and the two cooperate to amplify the collimated laser beam into an annular collimated laser beam. The annular collimated laser beam enters the parabolic reflector 6, and the parabolic reflector 6 focuses the annular laser beam onto the surface of the target material 5. The surface of the target material 5 ejects an ablation plume 7 under the action of laser ablation, and the ejection of the plume causes the target material 5 to obtain a recoil impulse. The laser light source 1, the aspheric lens 2, the first cone lens 3, the second cone lens 4, and the parabolic reflector 6 share a common optical axis.

[0042] The laser light source 1 is a semiconductor laser, and the laser working modes are divided into two types: continuous light emission and pulsed light emission. In the pulse working mode, the laser pulse width is adjustable. Pulse laser ablation will generate impulse, and continuous laser ablation will generate impulse accumulation in time, that is, thrust.

[0043] The aspheric lens 2 is used to collimate the outgoing laser of the laser light source 1. The focal position of the aspheric lens 2 coincides with the light outlet position of the laser light source 1. The collimated outgoing laser will be sent to the first conic lens 3. The aspheric lens 2 will not introduce spherical aberration when focusing or collimating. For a monochromatic light source, spherical aberration is often a factor that limits a single spherical lens from achieving diffraction-limited performance when focusing or collimating. Therefore, an aspheric lens is selected to collimate the outgoing laser.

[0044] The first axicon 3 is used to convert the collimated laser into a Bessel beam, and the Bessel beam is a ring-shaped beam.

[0045] like Figure 2 As shown, from the cross section of the annular beam, it is composed of an annular part surrounded by two inner and outer circles. The Bessel beam has the characteristics of non-diffraction and self-recovery.

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

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

[0048] In order to facilitate the processing of the parabolic reflector 6, a complete parabolic reflector is first designed and defined. The parabolic reflector is made of aluminum alloy material and then mirror polished or 3D printed and then mirror polished. According to the actual selected laser wavelength, the reflective surface is coated to form a high reflectivity parabolic reflector.

[0049] like Figure 3 As shown, after the processing is completed, according to the outer diameter and inner diameter of the collimated Bessel beam, the complete parabolic reflector is cut to retain the radius W using precision machining processes such as wire cutting or 3D printing technology. 1 and W 2 A parabolic reflector with a radius W 1 The radius W must be larger than the outer diameter of the Bessel annular beam. 2 It should be smaller than the inner diameter of the Bessel annular beam.

[0050] Assume that the generatrix equation of the parabolic reflector is (yr f ) 2 =2px, N is the opening end of the nozzle, if the horizontal coordinate of point N is defined as the axial length L of the nozzle n , the longitudinal coordinate is the nozzle opening radius R n ,but:

[0051]

[0052] Where l is the distance from the focus to the nozzle vertex, p is the parameter of the generatrix equation of the nozzle inner wall, L is the distance from the focus to the nozzle opening, r f is the radius of the focusing ring, which refers to the distance between the ideal focal position and the rotational symmetry axis and characterizes the shape of the energy deposition area.f = 0, indicating point focusing. 1 and W 2 It indicates the distance between the two ends of the parabolic reflector and the rotational symmetry axis.

[0053] Figure 1 The device for generating impulse by reflective ablation of Bessel laser beam shown in the figure has the following specific working process: a laser light source 1 emits a laser, which is collimated by an aspheric lens 2 and then enters a first conical lens 3. The generated Bessel beam is collimated by a second conical lens 4, and then the collimated Bessel beam is introduced into a parabolic reflector 6. Subsequently, the collimated Bessel beam is focused from all sides on the surface of a working fluid target material 5 in an oblique incident manner, and the surface of the target material is laser ablated. The laser ablation generates a plume jet 7, thereby generating impulse.

[0054] based on Figure 1 The device shown is a method for generating impulse by Bessel laser beam reflection ablation, comprising the following steps:

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

[0056] Step S2, using an aspheric lens to expand and collimate the laser beam;

[0057] Step S3, using a first axicon to convert the collimated laser into a Bessel beam;

[0058] Step S4, using a second axicon to collimate the Bessel beam;

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

[0060] Embodiment 1:

[0061] A laser is used as a laser light source 1 to generate a 1064 nm Gaussian continuous laser;

[0062] The Gaussian continuous laser is collimated using an aspheric lens 2 with a focal length of 10.5 mm and a diameter of 12 mm;

[0063] The collimated Gaussian continuous beam is converted into a Bessel beam using the first aconic lens 3 with a diameter of 12.7 mm and a bottom angle of 20°. The ring width of the Bessel beam remains constant during the propagation process. Although the inner and outer diameters of the Bessel beam are increasing with the increase of the transmission distance, the difference between the inner and outer diameters is constant. It can be seen from the schematic diagram of the Bessel beam that the width is constant, and the ring width is equal to the radius of the Gaussian continuous laser beam when it enters the first aconic lens 3;

[0064] The Bessel beam is collimated by using a second conical lens 4 with a diameter of 50.8 mm and a bottom angle of 20°. The collimated Bessel beam enters a parabolic reflector 6, which is formed by mirror polishing after being processed from an aluminum alloy material.

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

[0066] Since the recoil impulse can be generated, the Bessel laser beam reflection ablation device for generating impulse of the present invention can be used as a propulsion device for an aircraft in the outer space of the earth, and is used to use the generated recoil impulse as a propulsion force to push the aircraft to move. The present invention also provides an outer space aircraft, including the Bessel laser beam reflection ablation device for generating impulse, wherein the Bessel laser beam reflection ablation device for generating impulse is arranged outside the outer space aircraft, and is used to generate impulse to push the outer space aircraft to move.

[0067] The device for generating impulse by reflective ablation of a Bessel laser beam of the present invention uses a first and a second conical lens to convert the laser light emitted by the laser light source into an annular Bessel beam, and a parabolic reflector focuses the Bessel beam from all sides to the surface of a working fluid target material in an oblique incident manner to ablate and generate ablation impulse, thereby effectively avoiding surface contamination of optical elements caused by ablation plume injection. Since the Bessel beam has a non-diffraction characteristic, the laser is focused on the surface of the working fluid target material to generate a smaller area, more uniform, and neatly edged ablation spot, thereby obtaining a higher laser power density and a more consistent light energy distribution, so that the impulse generated by ablation has better repeatability and stability, the target material ablation is more uniform, and the ablation surface tends to be smoother and more consistent.

[0068] Although the present invention is described herein in conjunction with various embodiments, in the process of implementing the claimed invention, those skilled in the art may understand and implement other variations of the disclosed embodiments by viewing the drawings, the disclosure, and the drawings, etc. In the specification, the word "comprising" does not exclude other components or steps, and "one" or "an" does not exclude multiple situations. A single processor or other unit can implement several functions listed in the specification. Certain measures are recorded in different embodiments, but this does not mean that these measures cannot be combined to produce good results.

[0069] Although the present invention has been described in conjunction with specific features and embodiments thereof, it is apparent that various modifications and combinations may be made thereto without departing from the spirit and scope of the present invention. Accordingly, this specification and the accompanying drawings are merely exemplary illustrations of the present invention and are deemed to cover any and all modifications, variations, combinations or equivalents within the scope of the present invention. Obviously, those skilled in the art may make various modifications and variations to the present invention without departing from the spirit and scope of the present invention. Thus, the present invention is intended to include such modifications and variations if they fall within the scope of the present invention and its equivalents.

Claims

1. A device for generating impulse by Bessel laser beam reflection ablation, characterized in that: The device comprises: a target material, and a laser light source, an aspherical lens, a first aconic lens, a second aconic lens, and a parabolic reflector arranged on a common optical axis; The laser light source emits a laser beam, which enters a first axicon after being collimated by an aspheric lens. The first axicon and the second axicon are arranged opposite to each other in conical surface. The first axicon converts the collimated laser beam into a Bessel beam, and the second axicon collimates and amplifies the Bessel beam into an annular Bessel beam. The parabolic reflector focuses the annular Bessel beam onto the target surface, and the target surface ejects an ablation plume to generate impulse under the action of laser ablation.

2. The device for generating impulse by Bessel laser beam reflection ablation according to claim 1, characterized in that: The laser light source is a continuous semiconductor laser or a pulsed semiconductor laser.

3. The device for generating impulse by 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 light source.

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

5. The device for generating impulse by Bessel laser beam reflection ablation according to claim 4, characterized in that: The base angle of the first axicon is the same as the base angle of the second axicon.

6. The device for generating impulse by Bessel laser beam reflection ablation according to claim 1, characterized in that: The parabolic reflector is formed by processing aluminum alloy material and then mirror polishing, or by 3D printing aluminum alloy material and then mirror polishing. According to the actual selected laser wavelength, the reflective surface is coated to form a high-reflectivity parabolic reflector.

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

8. The device for generating impulse by Bessel laser beam reflection ablation according to claim 1, characterized in that: The generatrix equation of the parabolic reflector is (yr f ) 2 =2px, the horizontal coordinate of the open end of the parabolic reflector is the axial length L of the nozzle n , the longitudinal coordinate is the nozzle opening radius R n ,but: Where l is the distance from the focus to the nozzle vertex; p is the parameter of the generatrix equation of the inner wall of the nozzle; L is the distance from the focus to the nozzle opening; r f is the radius of the focusing ring, which refers to the distance between the ideal focal position and the axis of rotational symmetry. f When =0, it indicates point focus.

9. A method for generating impulse by Bessel laser beam reflection ablation based on the device of claim 1, characterized in that: The following steps are involved: Using a laser to emit laser, the laser is a continuous laser or a pulsed Gaussian laser; Use an aspheric lens to expand and collimate the laser beam; The collimated laser beam is converted into a Bessel beam using a first axicon; A second axicon is used to amplify and collimate the Bessel beam into a circular Bessel beam; A parabolic reflector is used to converge the annular Bessel beam from all sides to the target surface for ablation. Under the action of laser ablation, the target surface ejects an ablation plume to generate impulse.

10. An external space vehicle, characterized in that: The device for generating impulse by Bessel laser beam reflection ablation comprises the device described in any one of claims 1 to 8, wherein the device for generating impulse by Bessel laser beam reflection ablation is arranged outside the external space vehicle and is used to generate impulse to drive the external movement of the external space vehicle.

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