CN218767619U - Laser beam expander with high damage threshold - Google Patents
Laser beam expander with high damage threshold Download PDFInfo
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- CN218767619U CN218767619U CN202223032185.3U CN202223032185U CN218767619U CN 218767619 U CN218767619 U CN 218767619U CN 202223032185 U CN202223032185 U CN 202223032185U CN 218767619 U CN218767619 U CN 218767619U
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Abstract
The utility model discloses a laser beam expander with high damage threshold, this laser beam expander includes first component and the second component that sets gradually along the light path, wherein, the input surface of first component is for cutting the plane and not plated the antireflection coating, the output face of second component is for cutting the plane; the light beam is incident to the first element at the Brewster angle, travels a certain distance L after exiting the first element to reach the second element, and then exits at the Brewster angle via the output face of the second element. The utility model discloses set up the light beam incident surface and be the miscut plane, and do not plate and establish the antireflection coating to increase laser beam expander's life, reduce reflection loss simultaneously, avoid reflecting the adverse effect of light back.
Description
Technical Field
The utility model relates to a laser equipment technical field, in particular to laser beam expander who possesses high damage threshold value.
Background
In practical applications of lasers, a laser beam expander is generally required to expand the light beam output by the laser to a proper multiple. Because the light spot directly output by the laser is generally small, the incident surface of the laser beam expander needs to bear high energy density (or peak power density), and particularly for ultraviolet bands, the antireflection film on the incident surface of the laser beam expander is easily damaged, so that the service life of the beam expander is limited.
For ultraviolet 355nm wave band, the damage threshold and the long-term service life of the antireflection film are restricted due to material doping, and the damage threshold of 5J/cm can be realized at the current industrial higher coating level 2 However, even under laser irradiation conditions below the damage threshold, material denaturation occurs over a long period of time, affecting the energy distribution of the transmitted beam, and reducing the performance index and lifetime of the laser. For the ultraviolet fused quartz material without the coating film, the damage threshold value generally reaches 20J/cm 2 In the above, the long-term life under the irradiation of the ultraviolet laser under the same conditions is much longer than that of the antireflection film.
If the incident surface is not coated to increase the service life, the power loss of the laser beam expander is increased (for example, the reflection loss of each incident surface is increased by 4%), and the reflected back light has adverse effect on the inside of the laser. Fig. 1 and 2 show two conventional laser beam expander structures in the prior art, both of which are composed of two lenses with focal lengths F1 and F2, respectively. Wherein, fig. 1 is composed of a negative lens and a positive lens, and the distance between the optical centers of the two lenses is F2-F1. Fig. 2 is composed of two confocal positive lenses, and the distance between the optical centers of the two lenses is F1+ F2. In the laser beam expanders of fig. 1 and 2, the lens surfaces are coated with antireflection coatings to reduce end face reflection loss, but also suffer from damage due to high energy density (or peak power density).
SUMMERY OF THE UTILITY MODEL
The embodiment of the utility model provides a laser beam expander with high damage threshold value aims at increasing the life of laser beam expander and reduces the reflection loss in the laser beam expander.
The embodiment of the utility model provides a laser beam expander with high damage threshold value, including first component and the second component that sets gradually along the light path, wherein, the input face of first component is for beveling plane and not plated the antireflection coating, the output face of second component is for beveling plane;
the light beam is incident to the first element at the Brewster angle, travels a certain distance L after exiting the first element to reach the second element, and then exits at the Brewster angle via the output face of the second element.
Preferably, the first element and the second element are both lenses, and the refractive indexes of the first element and the second element are both n;
brewster's angle θ of the chamfer plane of the first or second element B ＝arctan(n)；
The included angle beta = theta between the horizontal directions of the beveling plane of the first element and the beveling plane of the second element B 。
The embodiment of the utility model provides an among the first laser beam expander structure, the output face of first component is first interior concave surface, the radius of curvature of first interior concave surface is R1.
Preferably, the input surface of the second element is a first convex surface, and the radius of curvature of the first convex surface is R2, wherein R2 and R1 are in a multiple relation.
Preferably, a distance L = (R2-R1)/(n-1) between the first and second elements, where n is a refractive index of the first and second elements.
Preferably, the first inner concave surface and the first outer convex surface are both spherical surfaces or aspherical surfaces.
In a second laser beam expander structure provided in an embodiment of the present invention, the output surface of the first element is a second convex surface, and a curvature radius of the second convex surface is R1'.
Preferably, the input surface of the second element is a third convex surface, and the radius of curvature of the third convex surface is R2', wherein R2' and R1' are in a multiple relationship.
Preferably, a distance L = (R2 '+ R1')/(n-1) between the first and second elements, where n is the refractive index of the first and second elements.
Preferably, the second convex outer surface and the third convex outer surface are both spherical or aspherical.
The embodiment of the utility model provides a laser beam expander with high damage threshold value, this laser beam expander include along the first component and the second component that the light path set gradually, wherein, the input face of first component is for beveling plane and has not plated the antireflection coating, the output face of second component is beveling plane; the light beam is incident to the first element at the Brewster angle, travels a certain distance L after exiting the first element to reach the second element, and then exits at the Brewster angle via the output face of the second element. The embodiment of the utility model provides a set up the light beam incident surface and be the miscut plane, and do not plate and establish the antireflection coating to increase laser beam expander's life, reduce reflection loss simultaneously, avoid reflecting the adverse effect of light back.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without any creative effort.
FIG. 1 is a schematic diagram of a prior art laser beam expander;
FIG. 2 is a schematic diagram of another prior art laser beam expander;
fig. 3 is a schematic structural diagram of a laser beam expander with a high damage threshold according to an embodiment of the present invention;
fig. 4a and fig. 4b are schematic cross-sectional views of a first element and a second element of a laser beam expander having a high damage threshold according to an embodiment of the present invention;
fig. 5 is another schematic structural diagram of a laser beam expander with a high damage threshold according to an embodiment of the present invention;
fig. 6 is an angle relationship schematic diagram of a laser beam expander with a high damage threshold according to an embodiment of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be described clearly and completely with reference to the accompanying drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, not all, of the embodiments of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by a person skilled in the art without creative work belong to the protection scope of the present invention.
It will be understood that the terms "comprises" and/or "comprising," when used in this specification and the appended claims, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.
It is also to be understood that the terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used in the specification and the appended claims, the singular forms "a", "an", and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.
It should be further understood that the term "and/or" as used in the specification and the appended claims refers to any and all possible combinations of one or more of the associated listed items, and includes such combinations.
Referring to fig. 3, a laser beam expander with a high damage threshold according to an embodiment of the present invention includes a first element 100 and a second element 200 sequentially disposed along an optical path, wherein an input surface of the first element 100 is a bevel plane and is not plated with an anti-reflection film, and an output surface of the second element 200 is a bevel plane;
the light beam is incident on said first element 100 at brewster's angle and travels a certain distance L after exiting said first element 100 to reach said second element 200 and then exits at brewster's angle via the output face of said second element 200.
In this embodiment, the laser beam expander includes a first element 100 and a second element 200, wherein an input surface of the first element 100, on which a light beam is received, is a chamfered plane, so that the light beam can be incident at a brewster angle, and reflection loss is reduced, and meanwhile, since the input surface of the first element 100 is not coated with an antireflection film, damage to the input surface is avoided, and thus, the service life of the laser beam expander can be prolonged. In addition, the output surface of the second element 200 is also a beveled plane, and an antireflection film is not plated, so that the light beam can be emitted again at the brewster angle after being expanded, the damage is avoided, the reflection loss of the light beam is reduced, the adverse effect of reflected return light is avoided, and the energy effect of the emitted light beam is ensured. In a specific application scenario, the first element 100 and the second element 200 may be both lenses.
In one embodiment, the refractive indices of the first element 100 and the second element 200 are both n.
Further, the brewster angle θ of the chamfer plane of the first element 100 or the second element 200 B ＝ arctan(n)；
The included angle β = θ between the horizontal direction of the chamfer plane of the first element 100 and the chamfer plane of the second element 200 B 。
In this embodiment, when the refractive indexes of the first element 100 and the second element 200 are n, the brewster angle of the chamfer plane is θ B = arctan (n) and the angle between the two bevels β = θ B . For the light beam output through the output face of the first element 100, the angle from the incident light beam is: α =2 θ B -90 °. For example, when fused quartz is used as the material of the first element 100 and the second element 200, the refractive index at 355nm is n =1.4761, and the brewster angle θ can be calculated accordingly B ＝ arctan(n)＝55.9°，α＝2*θ B -90°＝21.8°。
In one embodiment, as shown in fig. 4a and 4b, the output surface of the first element 100 is a first concave surface, and the radius of curvature of the first concave surface is R1.
And the input surface of the second element 200 is a first outer convex surface, the radius of curvature of the first outer convex surface is R2, wherein R2 and R1 are in a multiple relation.
Further, a distance L = (R2-R1)/(n-1) between the first and second elements 100 and 200, where n is a refractive index of the first and second elements 100 and 200.
In this embodiment, the output surface of the first element 100 is a concave curved surface, i.e., the first concave surface, and has a radius of curvature R1, and the incident surface of the second element 200 is a convex curved surface, i.e., the first convex surface, and has a radius of curvature R2. Furthermore, the first inner concave surface and the first outer convex surface are both plated with antireflection films to prevent reflection loss and improve the light beam transmittance, and meanwhile, the first inner concave surface and the first outer convex surface may be spherical or aspherical. The light beam enters at the brewster angle without reflection loss, then passes through the first concave curved surface to enable the light beam to be diverged and emitted, after the light beam is transmitted for a specific distance L, the light spot of the light beam is diverged to a larger size, then the light beam enters the second element 200, the incident surface of the second element is a first outer convex surface coated with an antireflection film, the originally diverged light beam is collimated through the first outer convex surface, finally the light beam is emitted from the beveling plane of the second element 200 at the brewster angle, the emitted light beam is parallel to the incident light beam, and the beam expansion multiple of the light beam is R2/R1, for example, for 3 times of beam expansion, R2/R1=3.
In another embodiment, as shown in FIG. 5, the output face of the first element 100 is a second convex outer surface having a radius of curvature R1'.
And the input surface of the second element 200 is a third convex surface, and the radius of curvature of the third convex surface is R2', wherein R2' and R1' are in a multiple relation.
That is, the output surface of the first element 100 may be the second convex surface in addition to the first concave surface, and correspondingly, the input surface of the second element 200 may be the third convex surface in addition to the first convex surface. When the first element 100 is provided with a second convex surface and the second element 200 is provided with a third convex surface, the curvature radii of the two are also in a multiple relation, i.e. R2 'is a plurality of times of R1'.
In a specific embodiment, the second convex surface and the third convex surface are both plated with antireflection films, so that reflection loss is prevented, and the light beam transmittance is improved. In addition, the first inner concave surface and the first outer convex surface may be spherical or aspherical.
Further, a distance L = (R2 '+ R1')/(n-1) between the first element 100 and the second element 200, where n is a refractive index of the first element 100 and the second element 200.
In a specific embodiment, as shown in fig. 6, taking 3 times of beam expansion as an example, that is, the first inner concave surface R1=12mm of the first element 100, the first outer convex surface R2=36mm of the second element 200, the first element 100 and the second element 200 are made of fused silica, and the refractive index n =1.4761 at 355nm, then θ is calculated B ＝ arctan(n)＝55.9°，α＝2*θ B 90 ° =21.8 ° the arrangement shown in fig. 3 is used, i.e. the output face of the first element 100 is a first inner concave face and the input face of the second element 200 is a first outer convex face, then the spacing between the first element 100 and the second element 200 is: l = (R2-R1)/(n-1) =50.4mm.
Further, taking the beam expansion of a high-power Q-switched nanosecond ultraviolet laser as an example, the output wavelength of the laser is 355nm, the average power is 50W, the repetition frequency is 50kHz, the output spot size is 0.6mm, the single-pulse energy is 1mJ, and the energy density is 353mJ/cm 2 . For a conventional 3-time beam expander, under the long-term irradiation of the conventional 3-time beam expander under the condition, the antireflection film layer of the incident surface is easy to generate material denaturation or damage, so that the service life of the laser beam expander is not long. And if use the utility model discloses the laser beam expander that provides, the incident plane of laser beam expander need not plate the antireflection coating promptly to make the light beam with cloth jue siAnd when the light is incident at a special angle, the end face reflection loss cannot be generated, the damage threshold value can be improved, and the service life is prolonged.
The embodiments are described in a progressive manner in the specification, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other. For the system disclosed by the embodiment, the description is relatively simple because the system corresponds to the method disclosed by the embodiment, and the relevant points can be referred to the method part for description. It should be noted that, for those skilled in the art, it is possible to make several improvements and modifications to the present application without departing from the principle of the present application, and such improvements and modifications also fall within the scope of the claims of the present application.
It is further noted that, in the present specification, relational terms such as first and second, and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrases "comprising a," "8230," "8230," or "comprising" does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises the element.
Claims (10)
1. A laser beam expander with a high damage threshold value is characterized by comprising a first element and a second element which are sequentially arranged along an optical path, wherein the input surface of the first element is a beveled plane and is not plated with an antireflection film, and the output surface of the second element is a beveled plane;
the light beam is incident to the first element at the Brewster angle, travels a certain distance L after exiting the first element to reach the second element, and then exits at the Brewster angle via the output face of the second element.
2. The laser beam expander with high damage threshold of claim 1, wherein said first and second elements are both lenses, and said first and second elements have refractive indices of n;
brewster's angle θ of the chamfer plane of the first or second element B ＝arctan(n)；
The included angle beta = theta between the horizontal directions of the beveling plane of the first element and the beveling plane of the second element B 。
3. The laser beam expander with high damage threshold of claim 1, wherein the output face of the first element is a first concave inner face having a radius of curvature R1.
4. The laser beam expander with high damage threshold as claimed in claim 3, wherein the input surface of the second element is a first convex surface having a radius of curvature R2, wherein R2 is a multiple of R1.
5. The laser beam expander with high damage threshold of claim 4, wherein the spacing between the first and second elements is L = (R2-R1)/(n-1) where n is the refractive index of the first and second elements.
6. The laser beam expander with high damage threshold as claimed in claim 1, wherein the output face of the first element is a second convex outer face having a radius of curvature R1'.
7. The laser beam expander with high damage threshold as claimed in claim 6, wherein the input surface of the second element is a third convex surface having a radius of curvature R2', wherein R2' is a multiple of R1'.
8. The laser beam expander with high damage threshold as claimed in claim 7, wherein the spacing between the first and second elements is L = (R2 '+ R1')/(n-1), where n is the refractive index of the first and second elements.
9. The laser beam expander with high damage threshold of claim 4, wherein said first inner concave surface and said first outer convex surface are both spherical or aspherical.
10. The laser beam expander with high damage threshold of claim 7, wherein said second and third outer convex surfaces are both spherical or aspherical.
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| Application Number | Priority Date | Filing Date | Title |
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| CN202223032185.3U CN218767619U (en) | 2022-11-15 | 2022-11-15 | Laser beam expander with high damage threshold |
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| CN202223032185.3U CN218767619U (en) | 2022-11-15 | 2022-11-15 | Laser beam expander with high damage threshold |
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