Focusing system and laser-supported plasma light source

Abstract

The invention provides a focusing system and a laser-supported plasma light source. The focusing system comprises a collimating mirror, a beam expander and a focusing mirror which are sequentially arranged along a light path, the collimating mirror converts divergent laser beams into parallel beams and inputs the parallel beams into the beam expander; the beam expander is used for magnifying the beam waist diameter of the parallel light beams to be matched with the required F number and inputting the F number into the focus lens; the focus lens converges the parallel light beams again so as to excite and maintain the plasma light source. Compared with the prior art, the focusing system provided by the invention is excellent in optical performance, good in focusing effect, capable of maintaining the plasma light source and enabling the plasma light source to maintain excellent performance, and low in manufacturing cost.

Description

Technical Field

[0001] The present disclosure relates to the technical field of optical systems, and particularly to a focusing system and a laser-supported plasma light source. Background Art

[0002] A laser-supported plasma light source is a type of technical device that utilizes the interaction between a laser and matter to generate a plasma and relies on the plasma to emit light to provide a light source. Common ones include a laser-produced plasma (LPP), a laser-sustained plasma (LSP), etc.

[0003] Current research on laser-supported plasma light sources at home and abroad mainly focuses on the research of the F-number of the optical system and the shaping of the focused spot. For example, the comparison of the radiance and threshold power of the laser-supported plasma at different F-numbers, and the radiation performance of the laser-supported plasma under circular spots and flat-top light spots, etc. However, the research on the focusing system of the laser-supported plasma light source is less and lacks systematicness, which results in the existing laser-supported plasma light sources being unable to meet the actual working requirements. Summary of the Invention

[0004] The purpose of the present disclosure is to provide a focusing system and a laser-supported plasma light source to solve the problem that the existing focusing system cannot meet the actual working requirements.

[0005] An embodiment of the present disclosure provides a focusing system, including:

[0006] A collimating mirror, a beam expander, and a focusing mirror arranged in sequence along the optical path;

[0007] The collimating mirror is used to convert a divergent laser beam into a parallel beam and input it into the beam expander;

[0008] The beam expander is used to magnify the waist diameter of the parallel beam by a certain multiple to match the required F-number and input it into the focusing mirror;

[0009] The focusing mirror is used to converge the parallel beam again to excite and maintain the plasma light source.

[0010] In a possible implementation manner, the beam expander adopts a Galilean beam expander.

[0011] In a possible implementation manner, the Galilean beam expander includes a concave lens for input and a convex lens for output.

[0012] An embodiment of the present disclosure further provides a laser-supported plasma light source, including the focusing system, a laser light source, and a plasma light source described in the above embodiment;

[0013] The laser light source is disposed at the focal point of the collimating mirror and is used to emit a laser beam towards the focusing system;

[0014] The plasma light source is disposed at the focal point of the output of the focusing system.

[0015] In a possible implementation, the laser light source includes a single-mode fiber laser.

[0016] In a possible implementation, the wavelength of the laser light source is a near-infrared wavelength.

[0017] In a possible implementation, the numerical aperture of the light rays of the laser light source is 0.072.

[0018] In a possible implementation, the plasma light source includes a xenon lamp plasma light source.

[0019] The advantages of the present disclosure compared with the prior art are as follows:

[0020] The focusing system provided by the present disclosure includes: a collimating mirror, an expanding mirror, and a focusing mirror sequentially arranged along the optical path; the collimating mirror converts the divergent laser beam into a parallel beam and inputs it into the expanding mirror; the expanding mirror magnifies the beam waist diameter of the parallel beam by a multiple to match the required F number and inputs it into the focusing mirror; the focusing mirror reconverges the parallel beam to excite and maintain the plasma light source. Compared with the prior art, the focusing system provided by the present application has excellent optical performance, good focusing effect, can maintain the plasma light source and keep it in excellent performance, and has a lower manufacturing cost. Description of the Drawings

[0021] By reading the detailed description of the preferred embodiments below, various other advantages and benefits will become clear to those of ordinary skill in the art. The drawings are only for the purpose of showing the preferred embodiments and are not considered to be a limitation of the present disclosure. Moreover, throughout the drawings, the same reference numerals are used to represent the same components. In the drawings:

[0022] Figure 1 Shows a schematic structural diagram of a focusing system provided by the present disclosure;

[0023] Figure 2 Shows a schematic structural diagram of an expanding mirror in a focusing system provided by the present disclosure;

[0024] Figure 3 Shows a design flow chart of a focusing system provided by the present disclosure. Detailed Embodiments

[0025] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are merely exemplary and are not intended to limit the scope of the present disclosure. In addition, in the following description, descriptions of well-known structures and technologies are omitted to avoid unnecessarily confusing the concepts of the present disclosure.

[0026] Various schematic structural diagrams according to embodiments of the present disclosure are shown in the accompanying drawings. These figures are not drawn to scale, where for the purpose of clear expression, certain details are enlarged and certain details may be omitted. The shapes of various regions and layers shown in the figures, as well as their relative sizes and positional relationships, are merely exemplary and may deviate in practice due to manufacturing tolerances or technical limitations. Those skilled in the art can additionally design regions / layers with different shapes, sizes, and relative positions according to actual needs.

[0027] In the context of the present disclosure, when a layer / component is referred to as being "on" another layer / component, the layer / component can be directly on the other layer / component, or there can be an intermediate layer / component between them. Additionally, if a layer / component is "on" another layer / component in one orientation, then when the orientation is reversed, the layer / component can be "under" the other layer / component.

[0028] In the context of the present disclosure, when along the main optical path transmission direction, the optical element that the optical path passes through first is called the front, and the optical element that the optical path passes through later is called the rear.

[0029] To solve the problems existing in the prior art, embodiments of the present disclosure provide a focusing system and a laser-supported plasma light source, which will be described below with reference to the accompanying drawings.

[0030] Figure 1 A schematic structural diagram of a focusing system provided by an embodiment of the present application is shown, as Figure 1 shown, the focusing system includes: a collimating mirror 10, a beam expander 20, and a focusing mirror 30 arranged in sequence along the optical path.

[0031] The collimating mirror 10 is used to convert a divergent laser beam into a parallel beam and input it into the beam expander 20.

[0032] The collimating mirror is used to make a divergent beam more parallel, and its principle is based on the focusing property of a convex lens. When a divergent beam passes through a lens, the lens will focus the beam to the focal point. To achieve the collimation effect, the focal point of the collimating mirror is usually placed at the light source. In this way, the lens refocuses the divergent beam to make it parallel and can project it onto a distant target.

[0033] Specifically, if light rays emit from a point source, they will be focused on the focal point after passing through a lens. If light rays emit from an infinitely distant point, the lens will make the light rays parallel. By controlling the curvature and focal length of the lens, the collimator can adjust the light rays.

[0034] The light source can be a single-mode continuous fiber laser with a wavelength of 1080 nm. The single-mode fiber laser has good beam quality, which is beneficial to forming a small-sized focused spot. The numerical aperture NA of the light rays is about 0.072. The generated laser beam first passes through a collimator for collimation. The width D of the collimated parallel beam has the following relationship with the numerical aperture NA of the light rays and the focal length f of the collimator:

[0035]

[0036] It should be noted that the principle of the collimator is based on an ideal optical model and assumes that the light rays are monochromatic. In practical applications, factors such as wavelength, scattering, and aberration may need to be considered for their effects on the collimation effect.

[0037] The beam expander 20 is used to magnify the waist diameter of the parallel beam by a certain multiple to match the required F number and input it into the focusing lens.

[0038] Specifically, the beam expander adopts a Galilean beam expander. The Galilean beam expander includes a concave lens for input and a convex lens for output.

[0039] A beam expander is an optical element used to expand or reduce the diameter of a light beam. Its main principle is to adjust the light rays using a lens or mirror system. The most common type of beam expander originated from the Galilean telescope and usually includes a concave lens for input and a convex lens for output.

[0040] Figure 2 The following shows a schematic structural diagram of a beam expander in a focusing system provided by the present disclosure. As Figure 2 shown, the beam expander includes a concave lens for input and a convex lens for output. Their focal lengths and relative positions determine the beam expansion or focusing effect. The input lens transmits a virtual focal length beam to the output lens. Generally, low-magnification beam expanders are manufactured using this principle because it is simple, has a small volume, and a low price. Generally, it is designed to have as small a spherical aberration, as low a wavefront distortion, and achromatism as possible. Its limitation is that it cannot accommodate spatial filtering or perform high-magnification beam expansion.

[0041] The focusing lens 30 is used to converge the parallel beam again to excite and maintain the plasma light source.

[0042] The principle of the focusing lens is based on the focusing ability of the lens or mirror. Take the most common lens as an example, which can be divided into convex lenses and concave lenses. When light passes through the lens, the lens will bend the light and focus the light on a focal point.

[0043] For a convex lens, light enters from the side far away from the lens. After passing through the lens, it will bend towards the center and finally focus on a point on the side away from the lens, that is, the focal point. The following relationship exists:

[0044]

[0045] Among them, f is the focal length of the lens, d is the distance between the incident light and the lens, and di is the image distance, that is, the distance where the light is focused.

[0046] For a concave lens, light enters from the side close to the lens. After passing through the lens, it will diverge outward and there is no actual focal point.

[0047] To sum up, on the optical path, the focusing lens 10 is located behind the beam expander 20; the beam expander 20 is located behind the collimating lens 30. The light source inputs laser to the collimating lens 10, and the collimating lens 10 readjusts the laser beam with a certain divergence angle and inputs it into the beam expander 20; the beam expander 20 magnifies the beam waist diameter by a multiple to better match the desired F number; the focusing lens 30 then converges the ideal parallel light again and focuses it at the ideal position. The plasma light source that needs to be excited and maintained can be placed at the focal point for lighting and maintenance.

[0048] As Figure 3 shown, the design process of the above-mentioned focusing system provided by the present disclosure is as follows:

[0049] (1) Light source selection: It is planned to use a single-mode fiber laser as the driving light source. The single-mode fiber laser has good beam quality, which is beneficial to forming a small-sized focused spot;

[0050] (2) Design of the optical path system: After the light source emits a laser beam, a collimating lens is installed at the position before the light beam enters the conical mirror, which can be used to collimate the light beam and control the divergence angle of the light beam to improve the energy utilization rate;

[0051] (3) Focusing system simulation: Use ZEMAX to perform optical simulation on the focusing system, control the wavefront aberration, and achieve a focused spot size less than 100μm;

[0052] (4) Parameter adjustment: The surface curvature or other parameters of the conical mirror can be adjusted according to actual needs to achieve the required annular energy distribution spot.

[0053] The laser input is introduced by a collimating mirror. After passing through the optical system, it is focused on the ideal position. The plasma light source that needs to be excited and maintained can be placed at the focus for lighting and maintenance. Designed and optimized based on ZEMAX, the aberration of the wavefront is optimized to within 0.25 times the wavelength, and the radius of the blur spot in the spot diagram is optimized to within 10 μm to ensure that the laser-supported plasma light source has a high radiance.

[0054] It can be seen that through continuous optimization of the focusing system based on ZEMAX, an excellent focusing effect is obtained. The minimum focusing spot is less than 10 microns. The smaller the focusing spot, the better the performance of the laser-supported plasma light source can be obtained. And it has a large working distance, providing a relatively large operating space compared to other focusing systems. Therefore, the optical focusing system of the laser-supported plasma light source provided by the present disclosure has the advantages of a small focusing spot, a long working distance, a low manufacturing cost, and a high passing rate.

[0055] The embodiment of the present disclosure also provides a laser-supported plasma light source, including the focusing system, the laser light source, and the plasma light source described in the above embodiment; the laser light source is arranged at the focus of the collimating mirror and is used to emit a laser beam to the focusing system; the plasma light source is arranged at the focus output by the focusing system.

[0056] The laser light source inputs laser to the collimating mirror 10, and the collimating mirror 10 readjusts the laser beam with a certain divergence angle and inputs it into the beam expander 20; the beam expander 20 magnifies the beam waist diameter by a certain multiple to better match the desired F number; the focusing mirror 30 then converges the ideal parallel light again and focuses it on the plasma light source for lighting and maintenance.

[0057] In a possible implementation manner, the laser light source includes a single-mode fiber laser. The single-mode fiber laser has good beam quality, which is beneficial to forming a small-sized focusing spot.

[0058] In a possible implementation manner, the wavelength of the laser light source is a near-infrared wavelength, such as 1080 nm, and the numerical aperture of the light is 0.072. Of course, it can also be a laser light source with other wavelengths, and the present disclosure does not limit this.

[0059] In a possible implementation manner, the plasma light source includes a xenon lamp plasma light source. Of course, it can also be other plasma light sources, and the present disclosure does not limit this.

[0060] The advantages of the present disclosure compared with the prior art are as follows:

[0061] The focusing system provided by the present disclosure includes: a collimating mirror, a beam expander, and a focusing mirror sequentially arranged along the optical path; the collimating mirror converts the divergent laser beam into a parallel beam and inputs it into the beam expander; the beam expander magnifies the waist diameter of the parallel beam by a certain multiple to match the required F number and inputs it into the focusing mirror; the focusing mirror reconverges the parallel beam to excite and maintain the plasma light source. Compared with the prior art, the focusing system provided by this application has excellent optical performance, good focusing effect, can maintain the plasma light source and keep it in excellent performance, and has a lower manufacturing cost.

[0062] In order to form the same structure, those skilled in the art can also design methods that are not exactly the same as the methods described above. Additionally, although the above embodiments have been described separately, this does not mean that the measures in each embodiment cannot be used advantageously in combination.

[0063] The above describes the embodiments of the present disclosure. However, these embodiments are merely for illustrative purposes and not for limiting the scope of the present disclosure. The scope of the present disclosure is defined by the appended claims and their equivalents. Without departing from the scope of the present disclosure, those skilled in the art can make various substitutions and modifications, and these substitutions and modifications should all fall within the scope of the present disclosure.

Claims

1. A focusing system, characterized in that: include: A collimator, a beam expander and a focusing lens are sequentially arranged along the optical path; The collimator is used to convert the divergent laser beam into a parallel beam and input it into the beam expander; The beam expander is used to magnify the beam waist diameter of the parallel light beam to match the required F number and input it into the focusing lens; The focusing mirror is used to re-converge the parallel light beam to excite and maintain the plasma light source.

2. The focusing system according to claim 1, characterized in that: The beam expander is a Galilean beam expander.

3. The focusing system according to claim 2, characterized in that: The Galilean beam expander includes a concave lens for input and a convex lens for output.

4. A laser-supported plasma light source, characterized in that: The focusing system, laser light source and plasma light source according to any one of claims 1 to 3; The laser light source is arranged at the focus of the collimating mirror and is used to emit a laser beam to the focusing system; The plasma light source is arranged at the focus output by the focusing system.

5. The laser supported plasma light source according to claim 4, characterized in that: The laser light source includes a single-mode fiber laser.

6. The laser supported plasma light source according to claim 5, characterized in that: The wavelength of the laser light source is near infrared wavelength.

7. The laser supported plasma light source according to claim 6, characterized in that: The numerical aperture of the laser light source is 0.

072.

8. The laser supported plasma light source according to claim 4, characterized in that: The plasma light source includes a xenon lamp plasma light source.

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