A UV laser

Abstract

The embodiment of the present invention discloses an ultraviolet laser, including a fundamental frequency laser light source, a first frequency doubling structure and a second frequency doubling structure; the fundamental frequency laser light source emits a laser beam of a first wavelength; the first frequency doubling structure is located on the propagation path of the laser beam emitted by the fundamental frequency laser light source, and performs frequency doubling conversion on the laser beam of the first wavelength to generate a laser beam of a second wavelength; the first wavelength is twice the second wavelength; the second frequency doubling structure is located on the propagation path of the laser beam emitted by the first frequency doubling structure, and performs frequency doubling conversion on the laser beam of the second wavelength to generate a laser beam of a third wavelength; the second wavelength is twice the third wavelength; the ultraviolet laser also includes a beam shaping structure, which is located on the optical path between the first frequency doubling structure and the second frequency doubling structure, and is used to change the transmission and distribution of the laser beam of the second wavelength in space. The embodiment of the present invention reduces the generation of secondary light spots on both sides of the main light spot and improves the beam quality.

Description

Technical Field

[0001] The invention relates to the technical field of lasers, and in particular to an ultraviolet laser. Background Art

[0002] At present, ultraviolet lasers, especially 266nm deep ultraviolet lasers, are increasingly widely used in industrial manufacturing, biomedicine, semiconductor testing and other fields. 266nm deep ultraviolet lasers use the nonlinear effect of crystals to convert 1064nm lasers into 532nm lasers through two frequency doubling conversion processes, and then convert them into 266nm laser output.

[0003] Due to the limitations of the material properties of the crystal itself and other factors, there are fewer crystals to choose from in the second frequency doubling conversion process. Among them, the BBO crystal has the characteristics of low cost, high damage threshold, large effective nonlinear coefficient, large matching temperature range, and low deliquescent characteristics. It is the first choice for 266nm solid-state laser nonlinear crystals. However, the BBO crystal has a large walk-off angle, which will form an irregular elliptical spot, affecting the roundness of the laser spot and the beam quality. At the same time, the BBO crystal, especially the E-light vibration plane, has a small frequency doubling acceptance angle. Under high power conditions, the strongly convergent 532nm beam cannot take into account the smaller divergence angle, and light and dark stripes appear on both sides of the main spot, reducing the energy share of the main spot and making the beam quality worse. Summary of the invention

[0004] The embodiment of the present invention provides an ultraviolet laser, which reduces the generation of secondary light and dark stripes on both sides of the main spot of the laser beam, so that the energy of the laser beam is no longer dispersed, ensures high-quality beam output, reduces the damage rate of the beam shaping structure, and reduces costs.

[0005] According to one aspect of the present invention, there is provided an ultraviolet laser, comprising a fundamental frequency laser light source, a first frequency doubling structure and a second frequency doubling structure;

[0006] The fundamental frequency laser light source emits a laser beam of a first wavelength;

[0007] The first frequency doubling structure is located on the propagation path of the laser beam emitted by the fundamental frequency laser light source, and performs frequency doubling conversion on the laser beam of the first wavelength to generate a laser beam of a second wavelength; the first wavelength is twice the second wavelength;

[0008] The second frequency doubling structure is located on the propagation path of the laser beam emitted by the first frequency doubling structure, and performs frequency doubling conversion on the laser beam of the second wavelength to generate a laser beam of a third wavelength; the second wavelength is twice the third wavelength;

[0009] The ultraviolet laser also includes a beam shaping structure, which is located on the optical path between the first frequency doubling structure and the second frequency doubling structure and is used to change the transmission and distribution of the laser beam of the second wavelength in space.

[0010] Optionally, the beam shaping structure includes at least one collimating lens, and the at least one collimating lens is used to compress the divergence angle of the laser beam emitted by the first frequency doubling structure, and the divergence angle is smaller than the frequency doubling acceptance angle on the e-light vibration plane of the second frequency doubling structure.

[0011] Optionally, the beam shaping structure further includes a spot shaping component, which is located between the at least one collimating lens and the second frequency doubling structure and is used to compress the spot diameter entering the second frequency doubling structure and corresponding to the o-light vibration surface of the second frequency doubling structure.

[0012] Optionally, the light spot shaping component includes at least one cylindrical lens arranged along the laser emission light path.

[0013] Optionally, the second frequency doubling structure includes a quadruple frequency doubling crystal component, and the quadruple frequency doubling crystal component includes a bbo crystal, which is used to perform frequency doubling conversion on the laser beam of the second wavelength to generate the laser beam of the third wavelength.

[0014] Optionally, the quadruple frequency crystal assembly further includes a first constant temperature crystal furnace, which is a cylindrical structure and has an internal space for housing the bbo crystal, so as to provide a constant temperature environment for the bbo crystal.

[0015] Optionally, the second frequency doubling structure also includes a beam splitter prism, which is arranged behind the quadruple frequency doubling crystal component along the laser emission optical path, and is used to receive the laser light beams of the first wavelength, the second wavelength and the third wavelength emitted by the quadruple frequency doubling crystal component, and separate the laser light beams of the first wavelength, the second wavelength and the third wavelength at a certain angle before emitting.

[0016] Optionally, the second frequency doubling structure further includes a beam collector.

[0017] The beam collector is placed on one side of the outgoing light path of the beam splitter prism, and is used to collect the laser beams of the first wavelength and the second wavelength separated by a certain angle by the beam splitter prism.

[0018] Optionally, the first frequency doubling structure includes a double frequency crystal and a second constant temperature crystal furnace, wherein the double frequency crystal is used to perform frequency doubling conversion on the laser beam of the first wavelength to generate the laser beam of the second wavelength;

[0019] The second constant temperature crystal furnace is a cylindrical structure, and has an internal space for housing the doubled frequency crystal, so as to provide a constant temperature environment for the doubled frequency crystal.

[0020] Optionally, the first wavelength is 1064 nm.

[0021] The ultraviolet laser provided by the embodiment of the present invention comprises a fundamental frequency laser light source emitting a laser beam; a first frequency doubling structure performs frequency doubling conversion on the laser beam emitted by the fundamental frequency laser light source to generate a second wavelength laser beam with a shorter wavelength; a second frequency doubling structure performs frequency doubling conversion on the laser beam emitted by the first frequency doubling structure to generate a third wavelength laser beam with a shorter wavelength for output; a beam shaping structure is arranged between the first frequency doubling structure and the second frequency doubling structure to transform the spatial transmission and distribution of the second wavelength laser beam, and at the same time improve the ultraviolet frequency doubling efficiency, improve the walk-off, make the ultraviolet light energy distribution uniform, make the spot more round, reduce the generation of secondary light and dark stripes on both sides of the main spot of the laser beam, and make the energy of the laser beam no longer dispersed, thereby improving the quality of the beam and ensuring the output of high-quality laser beam.

[0022] It should be understood that the contents described in this section are not intended to identify the key or important features of the embodiments of the present invention, nor are they intended to limit the scope of the present invention. Other features of the present invention will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0024] Figure 1 A schematic diagram of the structure of a first ultraviolet laser provided in an embodiment of the present invention;

[0025] Figure 2 A schematic structural diagram of a second ultraviolet laser provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0026] In order to enable those skilled in the art to better understand the scheme of the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0027] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0028] Figure 1 The schematic diagram of the structure of the first ultraviolet laser provided by the embodiment of the present invention is shown in FIG. Figure 1 The ultraviolet laser includes a fundamental frequency laser light source 10, a first frequency doubling structure 20 and a second frequency doubling structure 30. The fundamental frequency laser light source 10 emits a laser beam of a first wavelength; the first frequency doubling structure 20 is located on the propagation path of the laser beam emitted by the fundamental frequency laser light source 10, and performs frequency doubling conversion on the laser beam of the first wavelength to generate a laser beam of a second wavelength; the first wavelength is twice the second wavelength; the second frequency doubling structure 30 is located on the propagation path of the laser beam emitted by the first frequency doubling structure 20, and performs frequency doubling conversion on the laser beam of the second wavelength to generate a laser beam of a third wavelength; the second wavelength is twice the third wavelength.

[0029] Exemplarily, the ultraviolet laser also includes a beam shaping structure 40, which is located on the optical path between the first frequency doubling structure 20 and the second frequency doubling structure 30, and is used to transform the spatial transmission and distribution of the laser beam (i.e., the laser beam of the second wavelength) emitted by the fundamental frequency laser light source 10. Laser frequency doubling utilizes the secondary nonlinear effect of nonlinear crystals under the action of strong lasers to generate frequency-doubled light with a frequency twice that of the original laser. Due to the properties of the nonlinear crystal itself, secondary light and dark stripes will be formed on both sides of the main spot of the laser beam of the third wavelength emitted by the second frequency doubling structure 30, reducing the energy proportion of the main spot, and the main spot walks off seriously, and the energy distribution is irregular, which affects the beam quality. Therefore, a beam shaping structure 40 is set to shape the transmitted second wavelength laser beam, reduce the formation of secondary stripes, improve walk-off, make the ultraviolet light energy distribution uniform, and make the spot rounder, thereby improving the beam quality.

[0030] Specifically, the frequency doubling to form the frequency doubling light needs to be obtained under the condition of phase matching. Since the frequency doubling acceptance angle of the e-light vibration plane of the nonlinear crystal is small, while the divergence angle is large, when the divergence angle is greater than the acceptance angle, a phase mismatch will occur, and secondary light spot stripes will be formed on both sides of the main light spot. At this time, the laser beam is dispersed, the energy proportion of the main light spot is reduced, and the beam quality is deteriorated. A beam shaping structure 40 is set between the first frequency doubling structure 20 and the second frequency doubling structure 30 to compress the divergence angle of the laser beam so that the divergence angle is smaller than the acceptance angle. At this time, the phase is matched, there are no secondary light spot stripes on both sides of the main light spot, and the energy of the laser beam is no longer dispersed, thereby improving the quality of the beam and ensuring high-quality beam output.

[0031] The ultraviolet laser provided by the embodiment of the present invention comprises a fundamental frequency laser light source emitting a laser beam; a first frequency doubling structure performs frequency doubling conversion on the laser beam emitted by the fundamental frequency laser light source to generate a laser beam with a shorter wavelength; a second frequency doubling structure performs frequency doubling conversion on the laser beam emitted by the first frequency doubling structure to generate a laser beam output with a shorter wavelength; a beam shaping structure is arranged between the first frequency doubling structure and the second frequency doubling structure to transform the spatial transmission and distribution of the second wavelength laser beam, and at the same time improve the ultraviolet frequency doubling efficiency, improve the walk-off, make the ultraviolet light energy distribution uniform, make the spot more round, reduce the generation of secondary light and dark stripes on both sides of the main spot of the laser beam, and the energy of the laser beam is no longer dispersed, thereby improving the quality of the beam and ensuring high-quality beam output.

[0032] Figure 2 The schematic diagram of the structure of the second ultraviolet laser provided in the embodiment of the present invention is shown in FIG. Figure 2 , the beam shaping structure 40 includes at least one collimating lens 41, and at least one collimating lens 41 is used to compress the divergence angle of the laser beam emitted by the first frequency doubling structure 20, so that the divergence angle is smaller than the frequency doubling acceptance angle on the e-light vibration plane of the second frequency doubling structure 30. When the divergence angle is large, the phase mismatch is aggravated, and the laser beam will be more dispersed, so that light and dark stripes are formed on both sides of the main spot of the laser beam. At this time, the energy of the main spot is reduced and the beam quality is reduced. The collimating lens 41 is set to convert the laser beam passing through the collimating lens 41 into parallel light. At this time, the beam waist of the laser beam converges to the second frequency doubling structure 30, and the divergence angle of the laser beam is reduced, so that the divergence angle is smaller than the acceptance angle, so as to avoid the appearance of light and dark stripes on both sides of the main spot of the laser beam and ensure the beam quality. The number of collimating lenses 41 can be set according to actual needs, and the embodiment of the present invention does not impose specific restrictions on this.

[0033] Exemplarily, the beam shaping structure 40 further includes a spot shaping component 42, which is located between at least one collimating lens 41 and the second frequency doubling structure 30, and is used to compress the spot diameter of the light beam entering the second frequency doubling structure 30 and corresponding to the o-light vibration plane of the second frequency doubling structure 30. Since the collimating lens 41 acts on light beams in two directions (i.e., o-light and e-light), the divergence angles of the light beams in two directions are reduced, the beam waist of the light spot is increased, and the spot diameter is increased. The frequency doubling efficiency is related to both the divergence angle and the spot diameter. When the spot diameter increases, the frequency doubling efficiency decreases, affecting the output efficiency of the laser. Due to the properties of the nonlinear crystal itself, the frequency doubling acceptance angle of the o-light vibration surface is larger, and the beam waist that can be allowed to pass is smaller. A spot shaping component 42 is set between the collimating lens 41 and the second frequency doubling structure 30 to compress the spot diameter of the o-light vibration surface and improve the frequency doubling efficiency. At the same time, the spot shaping component 42 will not affect the spot diameter of the e-light vibration surface, and will not affect the beam quality of the laser beam, thereby achieving high-power and high-quality laser output.

[0034] Exemplarily, the spot shaping component 42 includes at least one cylindrical lens arranged along the laser emission optical path. As an example, the spot shaping component 42 includes a convex cylindrical mirror 421 and a concave cylindrical mirror 422 arranged in sequence along the laser emission optical path. The cylindrical mirror has a one-dimensional magnification function, which can change the size of the imaging size. The convex cylindrical mirror 421 and the concave cylindrical mirror 422 are set to produce different effects on the laser beams in two directions, compressing the spot diameter of the o-light vibration surface, improving the frequency doubling efficiency, and at the same time not affecting the spot diameter of the e-light vibration surface, thereby ensuring the beam quality of the laser beam. In other embodiments, a prism can also be set to compress the spot diameter of the o-light vibration surface. The spot shaping component 42 can be set according to actual needs, and the present invention does not impose specific restrictions on this.

[0035] Exemplarily, the second frequency doubling structure 30 includes a quadruple frequency doubling crystal assembly 31, and the quadruple frequency doubling crystal assembly 31 includes a bbo crystal 311, which is used to perform frequency doubling conversion on the laser beam of the second wavelength to generate a laser beam of the third wavelength. The bbo crystal 311 (barium metaborate crystal) is a crystal with obvious comprehensive advantages and good performance in nonlinear optical crystals. It has an extremely wide light transmission range that can cover the deep ultraviolet band, an extremely low absorption coefficient, a high light damage threshold, broadband temperature matching, and excellent optical uniformity, which is conducive to improving the stability of the laser output power. At the same time, due to the properties of the bbo crystal 311 itself, the bbo crystal 311 walks off seriously, the receiving angle of the o light vibration plane is large, and the receiving angle of the e light vibration plane is small, and the two receiving angles have a large difference, so it is necessary to shape the laser beam to ensure the quality of the laser beam and the frequency doubling efficiency.

[0036] Specifically, the quadruple frequency crystal assembly 31 further includes a first constant temperature crystal furnace 312. The first constant temperature crystal furnace 312 is a cylindrical structure. The first constant temperature crystal furnace 312 has an internal space for housing the BBO crystal 311, and is used to provide a constant temperature environment for the BBO crystal 311. The BBO crystal 311 works in a constant temperature environment, which helps to improve the frequency doubling conversion efficiency and the stability of the optical power.

[0037] Exemplarily, the second frequency doubling structure 30 also includes a beam splitter prism 32, which is arranged behind the quadruple frequency doubling crystal component 31 along the laser emission optical path, and is used to receive the laser light beams of the first wavelength, the second wavelength and the third wavelength emitted by the quadruple frequency doubling crystal component 31, and separate the laser light beams of the first wavelength, the second wavelength and the third wavelength at a certain angle before emitting. Since the frequency doubling efficiency is not 100%, after the frequency doubling conversion of the first frequency doubling structure 20 and the second frequency doubling structure 30, a part of the laser light beams of the first wavelength and the second wavelength are still emitted, and the laser light beams of the three wavelengths are emitted in the same direction, so it is necessary to set the beam splitter prism 32 to separate the laser light beams of different wavelengths at a certain angle for facilitating the separation of the laser light beams of different wavelengths.

[0038] Exemplarily, the second frequency doubling structure 30 also includes a beam collector 33, which is placed on one side of the output light path of the beam splitter prism 32 and is used to collect the laser beams of the first wavelength and the second wavelength separated by a certain angle by the beam splitter prism 32. The laser beams of the first wavelength and the second wavelength that are still converted by the first frequency doubling structure 20 and the second frequency doubling structure 30 cannot be used as output lasers, and the laser beams of the first wavelength and the second wavelength need to be collected to avoid affecting the normal operation of the ultraviolet laser. Therefore, the beam collector 33 is arranged on one side of the output light path of the beam splitter prism 32 to collect the laser beams of the first wavelength and the second wavelength, so as to ensure that the ultraviolet laser only outputs the laser beam of the third wavelength, thereby ensuring the normal operation of the ultraviolet laser.

[0039] Exemplarily, the first frequency doubling structure 20 includes a double frequency crystal 21 and a second constant temperature crystal furnace 22. The double frequency crystal 21 is used to double the frequency of the laser beam of the first wavelength to generate a laser beam of the second wavelength; the second constant temperature crystal furnace 22 is a cylindrical structure, and the second constant temperature crystal furnace 22 has an internal space for housing the double frequency crystal 21, which is used to provide a constant temperature environment for the double frequency crystal 21. The double frequency crystal 21 doubles the frequency of the laser beam of the first wavelength to convert it into a laser beam of the second wavelength, and a high temperature and constant temperature working environment is set for the double frequency crystal 21. The non-critical phase matching method is used to help improve the frequency doubling conversion efficiency, while ensuring the roundness and symmetry of the laser beam, which is beneficial for the beam shaping structure 40 to shape the spot of the laser beam for output. The type of the double frequency crystal 21 can be set according to actual needs, and the embodiment of the present invention does not impose specific restrictions on this.

[0040] Exemplarily, the first wavelength is 1064nm. When the first wavelength is 1064nm, the second wavelength is 532nm, and the third wavelength is 266nm. The 266nm ultraviolet laser has the characteristics of high peak power, high repetition rate, narrow pulse width, and high stability, and is a commonly used laser in the detection field. In other embodiments, the wavelength of the laser beam can be set according to actual needs, and the embodiment of the present invention does not specifically limit this.

[0041] The above specific implementations do not constitute a limitation on the protection scope of the present invention. It should be understood by those skilled in the art that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modification, equivalent substitution and improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. An ultraviolet laser, characterized in that: It includes a fundamental frequency laser light source, a first frequency doubling structure and a second frequency doubling structure; The fundamental frequency laser light source emits a laser beam of a first wavelength; The first frequency doubling structure is located on the propagation path of the laser beam emitted by the fundamental frequency laser light source, and performs frequency doubling conversion on the laser beam of the first wavelength to generate a laser beam of a second wavelength; the first wavelength is twice the second wavelength; The second frequency doubling structure is located on the propagation path of the laser beam emitted by the first frequency doubling structure, and performs frequency doubling conversion on the laser beam of the second wavelength to generate a laser beam of a third wavelength; the second wavelength is twice the third wavelength; The ultraviolet laser further comprises a beam shaping structure, which is located on the optical path between the first frequency doubling structure and the second frequency doubling structure and is used to change the transmission and distribution of the laser beam of the second wavelength in space; The beam shaping structure comprises at least one collimating lens, and the at least one collimating lens is used to compress the divergence angle of the laser beam emitted by the first frequency doubling structure, wherein the divergence angle is smaller than the frequency doubling acceptance angle on the e-light vibration plane of the second frequency doubling structure; The beam shaping structure further comprises a light spot shaping component, which is located between the at least one collimating lens and the second frequency doubling structure and is used to compress the light spot diameter entering the second frequency doubling structure and corresponding to the o-light vibration surface of the second frequency doubling structure; The light spot shaping component includes at least one cylindrical lens arranged along the laser emission light path.

2. The ultraviolet laser according to claim 1, characterized in that: The second frequency doubling structure includes a quadruple frequency doubling crystal component, and the quadruple frequency doubling crystal component includes a bbo crystal, which is used to perform frequency doubling conversion on the laser beam of the second wavelength to generate the laser beam of the third wavelength.

3. The ultraviolet laser according to claim 2, characterized in that: The quadruple frequency crystal assembly also includes a first constant temperature crystal furnace. The first constant temperature crystal furnace is a cylindrical structure. The first constant temperature crystal furnace has an internal space for housing the bbo crystal and is used to provide a constant temperature environment for the bbo crystal.

4. The ultraviolet laser according to claim 2, characterized in that: The second frequency doubling structure also includes a beam splitter prism, which is arranged behind the quadruple frequency doubling crystal component along the laser emission optical path, and is used to receive the laser light beams of the first wavelength, the second wavelength and the third wavelength emitted by the quadruple frequency doubling crystal component, and separate the laser light beams of the first wavelength, the second wavelength and the third wavelength at a certain angle before emitting.

5. The ultraviolet laser according to claim 4, characterized in that: The second frequency doubling structure further includes a beam dump, The beam collector is placed on one side of the outgoing light path of the beam splitter prism, and is used to collect the laser beams of the first wavelength and the second wavelength separated by a certain angle by the beam splitter prism.

6. The ultraviolet laser according to claim 1, characterized in that: The first frequency doubling structure includes a double frequency crystal and a second constant temperature crystal furnace, wherein the double frequency crystal is used to perform frequency doubling conversion on the laser beam of the first wavelength to generate a laser beam of the second wavelength; The second constant temperature crystal furnace is a cylindrical structure, and has an internal space for housing the doubled frequency crystal, so as to provide a constant temperature environment for the doubled frequency crystal.

7. The ultraviolet laser according to claim 1, characterized in that: The first wavelength is 1064 nm.

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