A narrow linewidth ultraviolet laser

Abstract

The present invention includes a pump source and a laser oscillation structure, wherein the pump source is used to provide pump light for the laser oscillation structure, the laser oscillation structure includes a crystal and a resonant cavity, which is used to absorb the pump light and generate ultraviolet laser, and the resonant cavity of the laser oscillation structure is a ring cavity structure, and a unidirectional ring laser oscillation optical path is formed in the laser oscillation structure, which is used to output narrow line width ultraviolet laser; the wavelength of the narrow line width ultraviolet laser is 261nm. Compared with the prior art, the present invention greatly reduces the volume of the ultraviolet laser with an optimized structural design, and realizes miniaturization; and provides a narrow line width ultraviolet laser with a shorter wavelength, that is, a narrow line width ultraviolet laser with a wavelength of 261nm, which is more conducive to energy concentration and also improves resolution, and is suitable for promotion and application in high-precision fields such as fluorescence absorption, Raman spectroscopy, gene detection, biochemical engineering, space optical communication and medical treatment.

Description

Technical Field

[0001] The invention relates to the field of laser technology, in particular to a narrow line width ultraviolet laser. Background Art

[0002] Ultraviolet lasers are widely used in biochemical engineering, communications, and medical fields. There are many ways to generate ultraviolet lasers, such as ultraviolet gas lamps, ultraviolet light-emitting diodes (LEDs), ultraviolet lasers, etc.; among them, ultraviolet gas lamps are low in price and high in power, but large in size, low in conversion efficiency, fragile, and short in life; ultraviolet LEDs have fast response speed, low power consumption, small size and mass, and long life, but low in power; ultraviolet lasers have high power, good beam quality, high resolution, and good directionality, but the driving power supply is large in size, low in conversion efficiency, and expensive.

[0003] Among the existing ultraviolet lasers, ultraviolet continuous wave laser light sources are mainly all-solid-state lasers based on external cavity frequency doubling and sum frequency conversion of nonlinear optical frequency conversion. Compared with other ultraviolet lasers such as excimer lasers, ion lasers and free electron lasers with non-solid-state design, large and complex structure, large power consumption and high cost, this all-solid-state ultraviolet laser has narrower spectral bandwidth, better beam quality, lower maintenance cost, higher efficiency, longer life and higher stability. Therefore, this all-solid-state ultraviolet laser is widely used in different fields such as precision material processing, optical data storage, spectroscopy, etc. However, the precision requirements for all-solid-state ultraviolet lasers in fields such as precision processing and optical storage are increasing day by day. Therefore, it is urgent to research and develop more miniaturized all-solid-state ultraviolet lasers to obtain better application effects. Summary of the invention

[0004] 1. Technical issues to be resolved

[0005] The purpose of the present invention is to provide a narrow-linewidth ultraviolet laser, preferably a laser crystal capable of generating a preset wavelength band, combined with a ring resonant cavity type, and an optimized structure to make it more miniaturized, and to improve the output efficiency of the narrow-linewidth ultraviolet laser, enhance stability, and be more suitable for application in fields with high requirements on volume, weight and precision.

[0006] (II) Technical solution

[0007] In order to solve the above technical problems, the present invention provides a narrow-linewidth ultraviolet laser, comprising a pump source and a laser oscillation structure, wherein the pump source is used to provide pump light for the laser oscillation structure; the laser oscillation structure comprises a crystal and a resonant cavity, which are used to absorb the pump light and generate ultraviolet laser; the resonant cavity included in the laser oscillation structure is a ring cavity structure, and a unidirectional ring laser oscillation optical path is formed in the laser oscillation structure, which is used to output narrow-linewidth ultraviolet laser; the wavelength of the narrow-linewidth ultraviolet laser is 261nm.

[0008] Furthermore, in the narrow linewidth ultraviolet laser described in the present invention, the laser oscillation structure includes two groups of crystals, namely a first crystal and a second crystal; the first crystal is used to absorb the pump light and generate a fundamental frequency laser; the second crystal is used to perform frequency conversion on the fundamental frequency laser and generate a frequency-doubled laser; the laser oscillation structure includes a resonant cavity with two structures, namely a three-mirror ring cavity structure and a four-mirror ring cavity structure, which are used to form a unidirectional ring laser oscillation light path to ensure the output of a narrow linewidth ultraviolet laser; the pump source has two groups, namely a first pump source and a second pump source; the first pump source and the second pump source are respectively located on both sides of the laser oscillation structure; the first pump source and the second pump source respectively provide pump light for the first crystal.

[0009] Preferably, in the narrow linewidth ultraviolet laser described in the present invention, the three-mirror annular cavity structure also includes a cavity mirror, an FP etalon, an isolation element, and an output mirror, wherein the cavity mirror has three groups, namely a first cavity mirror, a second cavity mirror and a third cavity mirror; the first crystal is arranged between the first cavity mirror and the second cavity mirror; the second crystal is arranged between the third cavity mirror and the output mirror; the output mirror is arranged between the second crystal and the second cavity mirror; the FP etalon and the isolation element are arranged in sequence between the first cavity mirror and the third cavity mirror.

[0010] Preferably, in the narrow linewidth ultraviolet laser described in the present invention, the first crystal is arranged at the midpoint of the line connecting the first cavity mirror and the second cavity mirror; the third cavity mirror is arranged on the perpendicular midline of the line connecting the first cavity mirror and the second cavity mirror.

[0011] Preferably, in the narrow linewidth ultraviolet laser of the present invention, the coating angles of the first cavity mirror and the second cavity mirror are the same; the coating angle of the third cavity mirror is set according to the following formula (1):

[0012]

[0013] Wherein, θ1 is the coating angle of the first cavity mirror and the second cavity mirror; θ2 is the coating angle of the third cavity mirror.

[0014] Preferably, in the narrow linewidth ultraviolet laser of the present invention, the mutual distances among the first cavity mirror, the second cavity mirror and the third cavity mirror are set according to the following formula (2):

[0015]

[0016] Wherein, L1 is the distance between the first laparoscope and the second laparoscope; L2 is the distance between the second laparoscope and the third laparoscope; L3 is the distance between the first laparoscope and the third laparoscope.

[0017] Preferably, in the narrow linewidth ultraviolet laser described in the present invention, the four-mirror annular cavity structure also includes cavity mirrors, FP etalons, isolation elements, and polarization elements, wherein the cavity mirrors have four groups, namely a first cavity mirror, a second cavity mirror, a third cavity mirror, and a fourth cavity mirror; the first crystal is arranged between the first cavity mirror and the second cavity mirror; the second crystal is arranged between the third cavity mirror and the fourth cavity mirror; the FP etalon is arranged between the second cavity mirror and the third cavity mirror; the polarization element and the isolation element are arranged in sequence between the third cavity mirror and the second crystal.

[0018] Preferably, in the narrow linewidth ultraviolet laser described in the present invention, the first crystal is arranged at the midpoint of the line connecting the first cavity mirror and the second cavity mirror; the second crystal is arranged at the midpoint of the line connecting the third cavity mirror and the fourth cavity mirror; the distance between the first cavity mirror and the fourth cavity mirror is equal to the distance between the second cavity mirror and the third cavity mirror.

[0019] Preferably, in the narrow linewidth ultraviolet laser described in the present invention, the coating angles of the first cavity mirror, the second cavity mirror, the third cavity mirror and the fourth cavity mirror are the same.

[0020] Preferably, in the narrow linewidth ultraviolet laser of the present invention, the mutual distances among the first cavity mirror, the second cavity mirror, the third cavity mirror and the fourth cavity mirror are set according to the following formula (3):

[0021]

[0022] In the formula, L1 is the distance between the first cavity mirror and the second cavity mirror; L2 is the distance between the second cavity mirror and the third cavity mirror; L3 is the distance between the third cavity mirror and the fourth cavity mirror; L4 is the distance between the first cavity mirror and the fourth cavity mirror; θ is the coating angle of the first cavity mirror, the second cavity mirror, the third cavity mirror and the fourth cavity mirror.

[0023] Furthermore, in the narrow linewidth ultraviolet laser described in the present invention, the pump source is a semiconductor laser, and the wavelength of the pump light is 444±1nm; the first crystal is any one of a Pr:YLF crystal, a Pr:LLF crystal and a Pr:GdLiF crystal; the second crystal is any one of a BBO crystal, a CLBO crystal, a PP-LBGO crystal, a KABO crystal, a KBBF crystal and a RBBF crystal; the narrow linewidth ultraviolet laser wavelength is any one of 261nm, 273nm, 302nm, 303.5nm, 320nm, 349nm and 360nm generated by the combination of the first crystal and the second crystal, preferably, the wavelength is 261nm.

[0024] Furthermore, in the narrow linewidth ultraviolet laser described in the present invention, the ultraviolet laser is a single-frequency laser.

[0025] (III) Beneficial effects

[0026] Compared with the prior art, the technical solution provided by the present invention greatly reduces the volume of the ultraviolet laser and realizes miniaturization with the preferred laser crystal and optimized structural design; and provides a shorter wavelength narrow linewidth ultraviolet laser, that is, a wavelength of 261nm ultraviolet laser, which is more conducive to energy concentration and also improves the resolution, and is suitable for promotion and application in high-precision fields such as fluorescence absorption, Raman spectroscopy, genetic testing, biochemical engineering, space optical communication and medical treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Schematic diagram of the structure of the narrow line width ultraviolet laser of the present invention (I);

[0028] Figure 2 Schematic diagram of the structure of the narrow linewidth ultraviolet laser of the present invention (II);

[0029] Figure 3 Schematic diagram of the structure of the narrow line width ultraviolet laser of the present invention (III);

[0030] Figure 4 It is a schematic structural diagram of a beam shaping device for a narrow linewidth ultraviolet laser of the present invention;

[0031] Figure 5 Schematic diagram of the structure of the narrow linewidth ultraviolet laser of the present invention (IV);

[0032] Figure 6 Schematic diagram of the structure of the narrow linewidth ultraviolet laser of the present invention (V);

[0033] Figure 7 Schematic diagram of the structure of the narrow line width ultraviolet laser of the present invention (VI);

[0034] Figure 8 Schematic diagram of the structure of the narrow line width ultraviolet laser of the present invention (VII);

[0035] Fig. 9 Schematic diagram of the structure of the narrow linewidth ultraviolet laser of the present invention (VIII);

[0036] Fig.10 Schematic diagram of the structure of the narrow line width ultraviolet laser of the present invention (IX);

[0037] Fig.11 Schematic diagram of the structure of the narrow linewidth ultraviolet laser of the present invention (X);

[0038] Fig.12 Schematic diagram of the structure of the narrow linewidth ultraviolet laser of the present invention (XI);

[0039] Fig.13 Schematic diagram of the structure of the narrow linewidth ultraviolet laser of the present invention (XII);

[0040] Fig.14 Schematic diagram of the structure of the narrow linewidth ultraviolet laser of the present invention (XIII);

[0041] Fig.15 Schematic diagram of the structure of the narrow linewidth ultraviolet laser of the present invention (XIV);

[0042] Fig.16 Schematic diagram of the structure of the narrow linewidth ultraviolet laser of the present invention (XV);

[0043] Fig.17 Schematic diagram of the structure of the narrow linewidth ultraviolet laser of the present invention (XVI);

[0044] Fig.18 Schematic diagram of the structure of the narrow linewidth ultraviolet laser of the present invention (XVII);

[0045] Fig.19 Schematic diagram of the structure of the narrow linewidth ultraviolet laser of the present invention (XVIII);

[0046] Fig. 20 Schematic diagram of the structure of the narrow linewidth ultraviolet laser of the present invention (XIX);

[0047] Fig.21 Schematic diagram of the structure of the narrow linewidth ultraviolet laser of the present invention (twenty);

[0048] Fig. 22 Structural schematic diagram of the narrow linewidth ultraviolet laser of the present invention (Twenty-one);

[0049] Fig.23 It is a schematic structural diagram of the narrow linewidth ultraviolet laser of the present invention (Twenty-two);

[0050] Fig.24 It is a schematic structural diagram of the narrow linewidth ultraviolet laser of the present invention (Twenty-three);

[0051] Fig.25 This is a schematic structural diagram of the narrow linewidth ultraviolet laser of the present invention (Twenty-four).

[0052] As shown in the figure:

[0053] 1-pump source, 101-first pump source, 101A-first A pump source, 101B-first B pump source, 102-second pump source, 102A-second A pump source, 102B-second B pump source;

[0054] 2-beam shaping device, 201-first beam shaping device, 202-second beam shaping device;

[0055] 3-half-wave plate, 301A-first A half-wave plate, 301B-first B half-wave plate, 302A-second A half-wave plate, 302B-second B half-wave plate;

[0056] 4-polarizer, 401-first polarizer, 402-second polarizer;

[0057] 5-laser oscillation structure, 501-first cavity mirror, 502-second cavity mirror, 503-third cavity mirror, 504-fourth cavity mirror, 505-output mirror, 506-first crystal, 507-second crystal, 508-FP etalon, 509-polarization element, 510-isolation element, 51001-Faraday rotator, 51002-half-wave plate element;

[0058] 6-beam focusing device, 601-first beam focusing device, 602-second beam focusing device;

[0059] 7- beam collimation device, 701- first beam collimation device, 702- second beam collimation device. DETAILED DESCRIPTION

[0060] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution 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 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 are within the scope of protection of the present invention.

[0061] In the following detailed description, many specific details are provided in order to provide a comprehensive understanding of the present invention. However, it is obvious to those skilled in the art that the present invention can be implemented without some of these specific details. The following description of the embodiments is only intended to provide a better understanding of the present invention by illustrating examples of the present invention.

[0062] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments. In order to avoid unnecessary confusion about the essence of the present invention, well-known components, circuits, and methods of use are not described in detail.

[0063] Example 1

[0064] like Figure 1 As shown, a narrow linewidth ultraviolet laser of the present invention comprises a pump source 1 and a laser oscillation structure 5, wherein the pump source 1 is used to provide pump light for the laser oscillation structure 5, the laser oscillation structure 5 comprises a crystal (not shown in the figure) and a resonant cavity (not shown in the figure), which are used to absorb the pump light and generate ultraviolet laser, and the resonant cavity of the laser oscillation structure 5 is a ring cavity structure, and a unidirectional ring laser oscillation optical path is formed in the laser oscillation structure 5, which is used to output narrow linewidth ultraviolet laser.

[0065] When the ultraviolet laser of the present invention in the above-mentioned embodiment is applied, the pump source 1 provides pump light to the laser oscillation structure 5, and the laser oscillation structure 5 absorbs the pump light and then generates the target ultraviolet laser. In the laser oscillation structure 5 with a ring cavity structure, the laser is transmitted in one direction to form a unidirectional ring laser oscillation light path, and finally outputs the target narrow linewidth ultraviolet laser.

[0066] In the above embodiment, in order to ensure the efficient output of the target narrow linewidth ultraviolet laser, the laser oscillation structure 5 includes two groups of crystals, the two groups of crystals are respectively a first crystal (not shown in the figure) and a second crystal (not shown in the figure), wherein the first crystal is used as a laser crystal to absorb the pump light and generate a fundamental frequency laser; the second crystal is used as a frequency doubling crystal to perform nonlinear frequency conversion on the fundamental frequency laser to generate a frequency doubling laser, i.e., the target ultraviolet laser. Preferably, the first crystal is any one of a Pr:YLF crystal, a Pr:LLF crystal and a Pr:GdLiF crystal, or other crystals having similar functions to the Pr:YLF crystal; the second crystal is any one of a BBO crystal, a CLBO crystal, a PP-LBGO crystal, a KABO crystal, a KBBF crystal and a RBBF crystal, or other crystals having similar functions to the BBO crystal. The wavelength of the fundamental frequency laser is any one of 522nm, 546nm, 604nm, 607nm, 640nm, 698nm, and 720nm, preferably, the wavelength is 522nm; the wavelength of the frequency-doubled laser, i.e., the target ultraviolet laser, is any one of 261nm, 273nm, 302nm, 303.5nm, 320nm, 349nm, and 360nm, preferably, the wavelength is 261nm. Specifically, in the laser oscillation structure with the ring cavity structure, the fundamental frequency laser is transmitted in one direction, thereby forming a unidirectional ring laser oscillation optical path to ensure the efficient generation and output of the target ultraviolet laser.

[0067] In the above embodiment, in order to ensure the efficiency and power of the target ultraviolet laser, the pump source is a continuous pump source, such as Figure 2As shown, preferably, the pump source has two groups, namely a first pump source 101 and a second pump source 102; the first pump source 101 and the second pump source 102 are respectively located on both sides of the laser oscillation structure; the first pump source 101 and the second pump source 102 respectively provide pump light for the first crystal; thus, by performing double-end pumping on the laser oscillation structure, it provides a guarantee for improving the efficiency and power of generating the target ultraviolet laser. Preferably, in order to ensure the acquisition of short-wave target ultraviolet laser, the wavelength of the pump light is preferably 444±1nm; therefore, preferably, the first pump source 101 and the second pump source 102 are both semiconductor lasers, and the semiconductor laser is preferably a 444±1nm LD or a 444±1nm fiber-coupled laser, the 444±1nm LD is a laser diode capable of emitting a wavelength of 444±1nm, and the power of the 444±1nm LD is preferably 4W to 5W, the 444±1nm fiber-coupled laser is a fiber-coupled semiconductor laser capable of emitting a laser with a wavelength of 444±1nm, and the average power of the 444±1nm fiber-coupled laser is preferably 20W to 60W; this arrangement is conducive to reducing costs, reducing the overall volume of the laser, and improving the generation efficiency and output power of the target ultraviolet laser.

[0068] Example 2

[0069] like Figure 3 As shown, a narrow linewidth ultraviolet laser of the present invention has the same basic structure and application as that of embodiment 1. Specifically, in order to obtain a target narrow linewidth ultraviolet laser with high beam quality, when the pump source 1 does not include a coupling device, as shown in FIG. Figure 3 As shown, a beam shaping device 2 and a half-wave plate 3 are sequentially arranged between the pump source 1 and the laser oscillation structure 5. The number of the beam shaping device 2 and the half-wave plate 3 is the same as that of the pump source 1. The beam shaping device 2 is arranged adjacent to the pump source 1, and the half-wave plate 3 is arranged adjacent to the laser oscillation structure 5. In specific applications, the pump light is beam shaped by the beam shaping device 2, and the shaped pump light beam is adjusted by the half-wave plate 3. Thus, after the pump light is processed by the combination of the beam shaping device 2 and the half-wave plate 3, a beam matching the cavity mode of the laser oscillation structure 5 is formed, and then enters the laser oscillation structure 5 for pumping, so as to maximize the use of the pump light to obtain the target narrow line width ultraviolet laser with high beam quality.

[0070] In the above embodiment, the half-wave plate 3 is a half-wave plate corresponding to the wavelength of the pump light. Based on the fact that the wavelength of the pump light is preferably 444±1nm, the half-wave plate 3 is preferably a half-wave plate for lasers with a wavelength of 444±1nm, that is, a half-wave plate (@444±1nm); so as to efficiently adjust the polarization direction of the pump light beam incident on the laser oscillation structure 5 so that it is in the direction of maximum absorption of the laser oscillation structure 5.

[0071] In the above embodiment, when the pump source 1 is 444±1 nm LD, Figure 4 As shown, the beam shaping device 2 preferably includes a cylindrical lens and a convex lens, wherein the cylindrical lens collimates the pump light, and the convex lens focuses the pump light collimated by the cylindrical lens to obtain a high-quality beam shaping effect.

[0072] In the above embodiment, preferably, Figure 5 As shown, when two groups of pump sources are provided based on double-ended pumping, namely, a first A pump source 101A and a second A pump source 102A, the beam shaping device 2 and the half-wave plate 3 are each provided with two groups, the two groups of beam shaping devices 2 are respectively a first beam shaping device 201 and a second beam shaping device 202, the two groups of half-wave plates 3 are respectively a first A half-wave plate 301A and a second A half-wave plate 302A, the first beam shaping device 201 is provided between the first A pump source 101A and the first A half-wave plate 301A, and the second beam shaping device 202 is provided between the second A pump source 102A and the second A half-wave plate 302A. In specific applications, outside the laser oscillation structure, the pump light is processed from both ends simultaneously, wherein the pump light emitted by the first A pump source 101A is beam shaped by the first beam shaping device 201, and then the pump light beam shaped by the first beam shaping device 201 is adjusted by the first A half-wave plate 301A; the pump light emitted by the second A pump source 102A is beam shaped by the second beam shaping device 202, and then the pump light beam shaped by the second beam shaping device 202 is adjusted by the second A half-wave plate 302A; thereby , after synchronously processing the pump lights at both ends by combining the two groups of beam shaping devices 2 and the two groups of half-wave plates 3, a beam matching the cavity mode of the laser oscillation structure 5 is formed, and then synchronously enters the first crystal from both ends of the laser oscillation structure 5, and performs double-end pumping on the first crystal, thereby maximizing the use of the pump light to obtain fundamental frequency light with high beam quality, and then facilitating the second crystal to perform nonlinear frequency conversion on the fundamental frequency laser to generate a frequency-doubled laser with high beam quality, that is, obtaining a target narrow-linewidth ultraviolet laser with high beam quality.

[0073] Example 3

[0074] like Figure 6As shown, a narrow linewidth ultraviolet laser of the present invention has the same basic structure and application as that of embodiment 1. Specifically, in order to obtain a target narrow linewidth ultraviolet laser with high beam quality, when the pump source includes a coupling device, as shown in FIG. Figure 6 As shown, a beam collimator 7, a polarizer 4, a half-wave plate 3 and a beam focusing device 6 are sequentially arranged between the pump source 1 and the laser oscillation structure 5. The number of the beam collimator 7, the polarizer 4, the half-wave plate 3 and the beam focusing device 6 is the same as that of the pump source 1. The beam collimator 7 is arranged adjacent to the pump source 1, and the beam focusing device 6 is arranged adjacent to the laser oscillation structure 5. In specific applications, the pump light emitted by the pump source 1 is first collimated by the beam collimator 7, the collimated pump light is polarized by the polarizer 4, the polarized light obtained after polarization splitting is polarized by the half-wave plate 3, and the polarized light after polarization direction adjustment is focused by the beam focusing device 6. Thus, after the pump light is processed by the combination of the beam collimator 7, the polarizer 4, the half-wave plate 3 and the beam focusing device 6, a beam matching the cavity mode of the laser oscillation structure 5 is formed, and then enters the laser oscillation structure 5 for pumping, so as to maximize the use of the pump light to obtain the target narrow line width ultraviolet laser with high beam quality.

[0075] In the above embodiment, the half-wave plate 3 is a half-wave plate corresponding to the wavelength of the pump light. Based on the fact that the wavelength of the pump light is preferably 444±1nm, the half-wave plate 3 is preferably a half-wave plate for lasers with a wavelength of 444±1nm, i.e., a half-wave plate (@444±1nm); the polarizer 4 is a polarizer corresponding to the wavelength of the pump light. Based on the fact that the wavelength of the pump light is preferably 444±1nm, the polarizer 4 is preferably a polarizer for lasers with a wavelength of 444±1nm, i.e., a polarizer (@444±1nm); this is to facilitate efficient adjustment of the polarization direction of the pump light beam incident on the laser oscillation structure 5, so that it is in the direction of maximum absorption of the laser oscillation structure 5.

[0076] In the above embodiment, when the pump source 1 is a 444±1 nm fiber-coupled laser, the beam collimating device 7 is preferably a convex lens to obtain a high-quality beam shaping effect.

[0077] In the above embodiment, in order to ensure a high-quality beam shaping effect, when the pump source 1 is a fiber-coupled laser, preferably, the ratio of the core diameter of the optical fiber to the spot diameter at the focus after shaping is preferably 2:1, 1:1 or 1:2, wherein the optical fiber is the coupled output optical fiber of the fiber-coupled laser, and the spot is a focused spot of the pump light incident on the first crystal after being shaped by the beam collimation device 7, the polarizer 4, the half-wave plate 3 and the beam focusing device 6 in sequence.

[0078] In the above embodiments, preferably, Figure 7 As shown, when two groups of pump sources are set based on double-ended pumping, namely, a first B pump source 101B and a second B pump source 102B, the beam collimating device 7, the polarizer 4, the half-wave plate 3 and the beam focusing device 6 are each provided with two groups, the two groups of beam collimating devices 7 are respectively a first beam collimating device 701 and a second beam collimating device 702, the two groups of polarizers are respectively a first polarizer 401 and a second polarizer 402, the two groups of half-wave plates are respectively a first B half-wave plate 301B and a second B half-wave plate 302B, the two groups of beam focusing devices are respectively a first beam focusing device 601 and a second beam focusing device 602, the first beam collimating device 701 is arranged between the first B pump source 101B and the first polarizer 401, and the second beam collimating device 702 is arranged between the second B pump source 102B and the second polarizer 402. In specific applications, outside the laser oscillation structure 5, the pump light is processed from both ends thereof at the same time, wherein the pump light emitted by the first B pump source 101B is collimated by the first beam collimation device 701, and the pump light collimated by the first beam collimation device 701 is then polarized and split by the first polarizer 401, and then the polarized pump light obtained after polarization splitting by the first polarizer 401 is adjusted in polarization direction by the first B half-wave plate 301B, and finally, the pump light after polarization direction adjustment by the first half-wave plate 301B is focused by the first beam focusing device 601; the pump light emitted by the second B pump source 102B is collimated by the second beam collimation device 702, and the pump light collimated by the second beam collimation device 702 is then polarized and split by the second polarizer 402, and then, the second B The half-wave plate 302B adjusts the polarization direction of the polarized pump light beam obtained after polarization splitting by the second polarizer 402, and finally, the second beam focusing device 602 focuses the pump light beam after polarization direction adjustment by the second B half-wave plate 302B; thus, through the above processing, pump light consistent with the maximum absorption polarization direction of the first crystal is obtained at both ends of the laser oscillation structure 5, and then synchronously enters the first crystal from both ends of the laser oscillation structure 5, respectively, to perform double-end pumping on the first crystal; thus, the above setting provides a guarantee for efficient utilization of the pump light with a high utilization rate, thereby facilitating the maximum utilization of the pump light to obtain fundamental frequency light with high beam quality, and then facilitating the generation of high beam quality frequency-doubled laser after the second crystal performs nonlinear frequency conversion on the fundamental frequency laser, that is, obtaining a target narrow-linewidth ultraviolet laser with high beam quality.

[0079] Example 4

[0080] like Figure 8-13As shown, a narrow linewidth ultraviolet laser of the present invention has the same basic structural arrangement and basic application as that of Example 1, or Example 2, or Example 3. In order to efficiently obtain the target narrow linewidth ultraviolet laser, specifically, the resonant cavity included in the laser oscillation structure 5 is a three-mirror ring cavity structure, including a cavity mirror, an FP etalon 508, an isolation element 510, and an output mirror 505, wherein the cavity mirror has three groups, namely a first cavity mirror 501, a second cavity mirror 502, and a third cavity mirror 503; the first crystal 506 is arranged between the first cavity mirror 501 and the second cavity mirror 502; the second crystal 507 is arranged between the third cavity mirror 503 and the output mirror 505; the output mirror 505 is arranged between the second crystal 507 and the second cavity mirror 502; the FP etalon 508 and the isolation element 510 are arranged between the first cavity mirror 501 and the third cavity mirror 503 in sequence.

[0081] In the above embodiment, in order to obtain the target narrow linewidth ultraviolet laser more efficiently, preferably, the first crystal 506 is arranged at the midpoint of the line connecting the first cavity mirror 501 and the second cavity mirror 502; the third cavity mirror 503 is arranged on the perpendicular midline of the line connecting the first cavity mirror 501 and the second cavity mirror 502.

[0082] In the above embodiment, in order to ensure the acquisition of the target narrow line width ultraviolet laser with high beam quality, preferably, the coating angles of the first cavity mirror 501 and the second cavity mirror 502 are the same; the coating angle of the third cavity mirror 503 is set according to the following formula (1):

[0083]

[0084] Wherein, θ1 is the coating angle of the first cavity mirror 501 and the second cavity mirror 502; θ2 is the coating angle of the third cavity mirror 503. More preferably, the mutual distances among the first cavity mirror 501, the second cavity mirror 502 and the third cavity mirror 503 are set according to the following formula (2):

[0085]

[0086] Wherein, L1 is the distance between the first cavity mirror 501 and the second cavity mirror 502; L2 is the distance between the second cavity mirror 502 and the third cavity mirror 503; L3 is the distance between the first cavity mirror 501 and the third cavity mirror 503; θ1 is the coating angle of the first cavity mirror 501 and the second cavity mirror 502.

[0087] In the above embodiment, the wavelength of the target narrow linewidth ultraviolet laser is preferably 261nm. The first cavity mirror 501 and the second cavity mirror 502 are used to enhance the transmittance of the pump light and to highly reflect the fundamental frequency laser. In order to efficiently obtain the target narrow linewidth ultraviolet laser, preferably, the first cavity mirror 501 and the second cavity mirror 502 are both dichroic mirrors, and are coated with dichroic films; the first cavity mirror 501 and the second cavity mirror 502 are both coated with an anti-reflection film for the pump light and a high reflection film for the fundamental frequency laser. Preferably, the coating angles of the first cavity mirror 501 and the second cavity mirror 502 are both 17°, and the first cavity mirror 501 and the second cavity mirror 502 are both coated with a 17°444nm anti-reflection film and a 17°522nm high-reflection film, wherein the reflectivity of the 17°522nm high-reflection film is preferably above 99.8%, and the transmittance of the 17°444nm anti-reflection film is preferably above 95%, and the transmittance of above 99.5% is particularly preferred; thereby, the first cavity mirror 501 and the second cavity mirror 502 can both be anti-reflective for the pump light with a wavelength of 444±1nm, and highly reflective for the fundamental frequency laser with a wavelength of 522nm, and on the first cavity mirror 501 and the second cavity mirror 502, the incident angle and reflection angle of the pump light with a wavelength of 444±1nm and the fundamental frequency laser with a wavelength of 522nm are both 17°. In the above embodiment, the third cavity mirror 503 is used to perform polarization selection on the fundamental frequency laser and perform anti-reflection and high reflection on the polarized fundamental frequency laser. In order to efficiently obtain the target narrow line width ultraviolet laser, preferably, the third cavity mirror 503 is a polarizer for the fundamental frequency laser; the third cavity mirror 503 is coated with a high reflection film and an anti-reflection film. Preferably, the third cavity mirror 503 is a polarizer for fundamental frequency laser with a wavelength of 522nm, and more preferably, the coating angle of the third cavity mirror 503 is 55.6°, and the third cavity mirror 503 is coated with a 55.6°522nm S-polarized light high-reflection film and a 55.6°522nm P-polarized light anti-reflection film, wherein the reflectivity of the 55.6°522nm S-polarized light high-reflection film is preferably above 99.8%, and the transmittance of the 55.6°522nm P-polarized light anti-reflection film is preferably above 95%, and the transmittance of above 99.5% is particularly preferred; thereby, the third cavity mirror 503 can achieve high reflection for S-polarized light with a wavelength of 522nm, and anti-reflection for P-polarized light with a wavelength of 522nm, and on the third cavity mirror 503, the incident angle and reflection angle of the S-polarized light with a wavelength of 522nm and the P-polarized light with a wavelength of 522nm are both 55.6°.

[0088] In the above embodiment, the output mirror 505 is used to enhance the transmittance of the fundamental frequency laser, and to highly reflect the doubled frequency laser and output the target narrow line width ultraviolet laser. In order to efficiently obtain the target narrow line width ultraviolet laser, preferably, the output mirror 505 is a dichroic mirror coated with a dichroic mold. Preferably, the output mirror 505 is coated with an anti-reflection film for the fundamental frequency laser and a high-reflection film for the frequency-doubled laser; more preferably, the coating angle of the output mirror 505 is 45°, and the output mirror 505 is coated with a 45°522nm anti-reflection film and a 45°261nm high-reflection film, wherein the transmittance of the 45°522nm anti-reflection film is preferably above 95%, and in particular, the transmittance of above 99.5% is preferred, and the reflectivity of the 45°261nm high-reflection film is preferably above 99.8%; thereby, the output mirror 505 can be anti-reflective for the fundamental frequency laser with a wavelength of 522nm, and highly reflective for the frequency-doubled laser with a wavelength of 261nm, and, on the output mirror 505, the incident angle and reflection angle of the fundamental frequency laser with a wavelength of 522nm and the frequency-doubled laser with a wavelength of 261nm are both 45°, so that the frequency-doubled laser, i.e., the target narrow-linewidth ultraviolet laser with a wavelength of 261nm, is coupled and output through the output mirror 505.

[0089] In the above embodiment, the isolation element 510 is used to isolate part of the fundamental frequency laser, wherein the running direction of the isolated fundamental frequency laser is opposite to the running direction of the ring laser oscillation optical path in the laser oscillation structure 5. In order to efficiently obtain the target narrow line width ultraviolet laser, preferably, the isolation element 510 includes a Faraday rotator 51001 and a half-wave plate element 51002, wherein the Faraday rotator 51001 is arranged between the FP etalon 508 and the half-wave plate element 51002, and the half-wave plate element 51002 is arranged between the Faraday rotator 51001 and the third cavity mirror 503; the isolation element 510 is an optical isolator for the fundamental frequency laser, preferably for the wavelength of 522 Preferably, the isolation element 510 comprises a Faraday rotator 51001 for the fundamental frequency laser with a wavelength of 522nm and a half-wave plate element 51002 for the fundamental frequency laser with a wavelength of 522nm, wherein the Faraday rotator 51001 for the fundamental frequency laser with a wavelength of 522nm is a Faraday rotator (@522nm), and the half-wave plate element 51002 for the fundamental frequency laser with a wavelength of 522nm is a half-wave plate (@522nm). Preferably, the Faraday rotator 51001, the half-wave plate element 51002 and the third cavity mirror 503 composed of a polarizer work together to ensure the unidirectional transmission of the laser in the laser oscillation structure 5, that is, in the laser oscillation structure 5 with a ring cavity structure, the laser in the opposite direction of the oscillation optical path of the ring laser is prevented from forming a ring oscillation optical path, thereby realizing the unidirectional transmission of the laser, and further facilitating the acquisition of the target narrow line width ultraviolet laser with high beam quality. Specifically, in the above embodiment, the running direction of the ring laser oscillation light path in the laser oscillation structure 5 is counterclockwise, and the laser running in the clockwise direction is prevented from forming a ring oscillation light path through the combined effect of the isolation element 510 and the third cavity mirror 503.

[0090] In the above embodiment, the FP etalon 508 is a Fabry-Perot (FP) etalon, which is used to narrow the line width of the fundamental frequency laser to form a fundamental frequency laser with high beam quality, thereby facilitating the formation of a frequency-doubled laser with high beam quality.

[0091] In the above embodiment, in order to more efficiently match the pump beam with the cavity mode of the laser oscillation structure 5, the laser oscillation structure 5 is set according to the specific situation, preferably by adjusting the cavity mirror specifications and the distance between the cavity mirrors; preferably, the first cavity mirror 501 and the second cavity mirror 502 are both plano-concave lenses, the third cavity mirror 503 is a plane mirror, the curvature of the first cavity mirror 501 is preferably -150 to -300 mm, the curvature of the second cavity mirror 502 is preferably -200 to -600 mm, the distance between the first cavity mirror 501 and the second cavity mirror 502 is preferably 50 to 150 mm, and the first crystal 506 is set at the midpoint of the line connecting the first cavity mirror 501 and the second cavity mirror 502. In addition, preferably, the second crystal 507 is set at the beam waist position close to the third cavity mirror 503 to improve the frequency doubling efficiency.

[0092] When the narrow linewidth ultraviolet laser of the present invention in the above embodiment is used, the basic application is the same as that of embodiments 1 to 3, and specifically, further includes: Figure 8-13 As shown, the pump light beam formed outside the laser oscillation structure 5 enters the laser oscillation structure 5 through the first cavity mirror 501 and / or the second cavity mirror 502 for transmission, and the first crystal 506 is single-ended (such as Figure 8 , Fig.10 and Fig.12 as shown) or double ended (as Fig. 9 , Fig.11 and Fig.13 As shown) pump, wherein a double-ended pump is preferred, that is: Fig. 9 , Fig.11 and Fig.13 As shown, the pump light beam is simultaneously enhanced through the first cavity mirror 501 and the second cavity mirror 502 to enter the laser oscillation structure 5 to perform double-end pumping on the first crystal 506; the pump light is absorbed by the first crystal 506 and a fundamental frequency laser is generated; the generated fundamental frequency laser is highly reflected by the first cavity mirror 501 and the second cavity mirror 502 respectively, wherein the counterclockwise fundamental frequency laser is generated by the first crystal 506 and then reflected by the first cavity mirror 501, and the line width is narrowed by the FP standard device 508 in turn, and the polarization state is kept unchanged after the action of the isolation element 510, and then reflected by the third cavity mirror 503 and enters the second crystal 507; the fundamental frequency laser is then subjected to nonlinear frequency conversion by the second crystal 507 and a frequency-doubled laser is generated, i.e., a target narrow-linewidth ultraviolet laser; finally, the frequency-doubled laser is highly reflected and output by the output mirror 505, i.e., a target narrow-linewidth ultraviolet laser with an output wavelength of 261nm.

[0093] In the above application process, the wavelength of the pump light is 444±1nm, the wavelength of the frequency-doubled laser, i.e., the target ultraviolet laser, is 261nm, and the wavelength of the fundamental frequency laser is 522nm; the first crystal 506 is any one of a Pr:YLF crystal, a Pr:LLF crystal, and a Pr:GdLiF crystal; the second crystal 507 is any one of a BBO crystal, a CLBO crystal, a PP-LBGO crystal, a KABO crystal, a KBBF crystal, and a RBBF crystal; in the laser oscillation structure 5 with a ring cavity structure, a ring laser oscillation optical path is formed, and its running direction is counterclockwise, that is, the fundamental frequency laser in the above application process oscillates in a counterclockwise direction along a ring optical path, and the frequency-doubled laser generated after passing through the second crystal 507 is output through the output mirror 505, thereby effectively ensuring the efficient generation and output of the target narrow-linewidth ultraviolet laser, i.e., a narrow-linewidth ultraviolet laser with a wavelength of 261nm.

[0094] In the above application process, in the laser oscillation structure 5, the isolation element 510 and the third cavity mirror 503 are combined to prevent the laser running in the clockwise direction from continuing to oscillate and transmit, thereby providing a guarantee for forming a counterclockwise ring laser oscillation optical path; specifically, the process in which the isolation element 510 and the third cavity mirror 503 prevent the clockwise fundamental frequency laser is as follows: based on the third cavity mirror 503 being a polarizer, and the isolation element 510 including a Faraday rotator 51001 and a half-wave plate element 51002, the fundamental frequency laser in the S polarization state generated by the first crystal 506 is reflected by the second cavity mirror 502 and then by the third cavity mirror 503. The three-cavity mirror 503 is highly reflective, and the reflected S-polarized light is rotated by the half-wave plate element 51002 and the Faraday rotator 51001 in turn to become P-polarized light. The formed P-polarized light is then transmitted clockwise and finally passes through the third cavity mirror 503, thereby increasing the cavity loss of the laser running in the clockwise direction and suppressing the clockwise operation of the laser, thereby providing a guarantee for realizing the counterclockwise unidirectional oscillation operation of the laser in the cavity, that is, forming a counterclockwise ring laser oscillation optical path, and then effectively suppressing the spatial hole burning effect, so as to ensure the efficient generation and output of the target narrow-linewidth ultraviolet laser, that is, a narrow-linewidth ultraviolet laser with a wavelength of 261nm.

[0095] Example 5

[0096] like Figure 14-19As shown, a narrow linewidth ultraviolet laser of the present invention has the same basic structural arrangement and basic application as that of Example 1, or Example 2, or Example 3. In order to efficiently obtain the target narrow linewidth ultraviolet laser, specifically, the resonant cavity included in the laser oscillation structure 5 is a four-mirror ring cavity structure, including cavity mirrors, FP etalon 508, isolation element 510, and polarization element 509, wherein the cavity mirrors have four groups, namely, a first cavity mirror 501, a second cavity mirror 502, a third cavity mirror 503, and a fourth cavity mirror 504; the first crystal 506 is arranged between the first cavity mirror 501 and the second cavity mirror 502; the second crystal 507 is arranged between the third cavity mirror 503 and the fourth cavity mirror 504; the FP etalon 508 is arranged between the second cavity mirror 502 and the third cavity mirror 503; the polarization element 509 and the isolation element 510 are arranged between the third cavity mirror 503 and the second crystal 507 in sequence.

[0097] In the above embodiment, in order to more efficiently obtain the target narrow linewidth ultraviolet laser with high beam quality, preferably, the first crystal 506 is arranged at the midpoint of the line connecting the first cavity mirror 501 and the second cavity mirror 502, and the second crystal 507 is arranged at the midpoint of the line connecting the third cavity mirror 503 and the fourth cavity mirror 504, and the distance between the first cavity mirror 501 and the fourth cavity mirror 504 is equal to the distance between the second cavity mirror 502 and the third cavity mirror 503; preferably, the coating angles of the first cavity mirror 501, the second cavity mirror 502, the third cavity mirror 503 and the fourth cavity mirror 504 are the same; preferably, the mutual distances between the first cavity mirror 501, the second cavity mirror 502, the third cavity mirror 503 and the fourth cavity mirror 504 are set according to the following formula (3):

[0098]

[0099] Wherein, L1 is the distance between the first cavity mirror 501 and the second cavity mirror 502; L2 is the distance between the second cavity mirror 502 and the third cavity mirror 503; L3 is the distance between the third cavity mirror 503 and the fourth cavity mirror 504; L4 is the distance between the first cavity mirror 501 and the fourth cavity mirror 504; θ is the coating angle of the first cavity mirror 501, the second cavity mirror 502, the third cavity mirror 503 and the fourth cavity mirror 504.

[0100] In the above embodiment, the first cavity mirror 501 and the second cavity mirror 502 are used to enhance the transmittance of the pump light and to highly reflect the fundamental frequency laser. In order to efficiently obtain the target narrow line width ultraviolet laser, preferably, the first cavity mirror 501 and the second cavity mirror 502 are both dichroic mirrors, and are coated with dichroic mode; the first cavity mirror 501 and the second cavity mirror 502 are both coated with an anti-reflection film for the pump light and a high reflection film for the fundamental frequency laser. Preferably, the coating angles of the first cavity mirror 501 and the second cavity mirror 502 are both 10°, and the first cavity mirror 501 and the second cavity mirror 502 are both coated with a 10°444±1nm anti-reflection film and a 10°522nm high-reflection film. The transmittance of the 10°444±1nm anti-reflection film is preferably above 99.5%, and the reflectivity of the 10°522nm high-reflection film is preferably above 99.8%. Thus, the first cavity mirror 501 and the second cavity mirror 502 can both enhance the transmittance of the pump light with a wavelength of 444±1nm and highly reflect the fundamental frequency laser with a wavelength of 522nm, and on the first cavity mirror 501 and the second cavity mirror 502, the incident angle and reflection angle of the pump light with a wavelength of 444±1nm and the fundamental frequency laser with a wavelength of 522nm are both 10°.

[0101] In the above embodiment, the third cavity mirror 503 is used to highly reflect the fundamental frequency laser. In order to efficiently obtain the target narrow line width ultraviolet laser, preferably, the third cavity mirror 503 is coated with a high reflection film. Preferably, the coating angle of the third cavity mirror 503 is 10°, and the third cavity mirror 503 is coated with a 10°522nm high reflection film, and the reflectivity of the 10°522nm high reflection film is preferably above 99.8%, thereby achieving the third cavity mirror 503 to be able to highly reflect the fundamental frequency laser with a wavelength of 522nm, and, on the third cavity mirror 503, the incident angle and reflection angle of the fundamental frequency laser with a wavelength of 522nm are both 10°.

[0102] In the above embodiment, the fourth cavity mirror 504 is used to highly reflect the fundamental frequency laser, enhance the transmittance of the doubled frequency laser and output the target narrow line width ultraviolet laser. In order to efficiently obtain the target narrow line width ultraviolet laser, preferably, the fourth cavity mirror 504 is a dichroic mirror coated with a dichroic mold. Preferably, the fourth cavity mirror 504 is coated with a high reflection film for the fundamental frequency laser and an anti-reflection film for the frequency doubled laser; more preferably, the coating angle of the fourth cavity mirror 504 is 10°, and the fourth cavity mirror 504 is coated with a 10°522nm high reflection film, wherein the reflectivity of the 10°522nm high reflection film is preferably above 99.8%, and the transmittance of the 10°261nm anti-reflection film is preferably above 95%, and the transmittance of above 99.5% is particularly preferred; thereby, the fourth cavity mirror 504 can be highly reflective for the fundamental frequency laser with a wavelength of 522nm, and can be anti-reflective for the frequency doubled laser with a wavelength of 261nm, and, on the fourth cavity mirror 504, the incident angle and reflection angle of the fundamental frequency laser with a wavelength of 522nm and the frequency doubled laser with a wavelength of 261nm are both 10°, so that the frequency doubled laser, i.e., the target narrow linewidth ultraviolet laser with a wavelength of 261nm, is efficiently output through the fourth cavity mirror 504.

[0103] In the above embodiment, the FP etalon 508 is a Fabry-Perot (FP) etalon, which is used to narrow the line width of the fundamental frequency laser to form a fundamental frequency laser with a narrow line width, thereby facilitating the formation of a narrow line width frequency doubled laser, and further facilitating the formation of a single-frequency target narrow line width ultraviolet laser.

[0104] In the above embodiment, the isolation element 510 is used to isolate part of the fundamental frequency laser, wherein the running direction of the isolated fundamental frequency laser is opposite to the running direction of the ring laser oscillation optical path in the laser oscillation structure 5. In order to efficiently obtain the target narrow line width ultraviolet laser, preferably, the isolation element 510 includes a Faraday rotator 51001 and a half-wave plate element 51002, wherein the Faraday rotator 51001 is arranged between the polarization element 509 and the half-wave plate element 51002, and the half-wave plate element 51002 is arranged between the Faraday rotator and the second crystal 507; the isolation element 510 is an optical isolator for the fundamental frequency laser, preferably for the wavelength of 522nm. Optical isolator for fundamental frequency laser; preferably, the isolation element 510 includes a Faraday rotator 51001 for the fundamental frequency laser with a wavelength of 522nm and a half-wave plate element 51002 for the fundamental frequency laser with a wavelength of 522nm, the Faraday rotator 51001 for the fundamental frequency laser with a wavelength of 522nm is a Faraday rotator (@522nm), and the half-wave plate element 51002 for the fundamental frequency laser with a wavelength of 522nm is a half-wave plate (@522nm).

[0105] In the above embodiment, the polarization element 509 is a polarizer, and the polarization element 509 and the isolation element 510 work together to ensure unidirectional transmission of laser light in the laser oscillation structure 5, that is, in the laser oscillation structure 5 with a ring cavity structure, the laser light running in the opposite direction to the allowed ring laser oscillation light path is prevented from forming a ring oscillation light path, thereby achieving unidirectional transmission of laser light, and further facilitating the acquisition of a single-frequency target narrow-linewidth ultraviolet laser.

[0106] In the above embodiment, in order to more efficiently match the pump beam with the cavity mode of the laser oscillation structure 5, the laser oscillation structure 5 is set according to specific working conditions, preferably by setting the specifications of the cavity mirrors and adjusting the distance between the cavity mirrors; preferably, the first cavity mirror 501 and the second cavity mirror 502 are both plane mirrors, and the distance between the first cavity mirror 501 and the second cavity mirror 502 is preferably 50 to 150 mm, and the first crystal 506 is arranged at the midpoint of the line connecting the first cavity mirror 501 and the second cavity mirror 502. In addition, the third cavity mirror 503 and the fourth cavity mirror 504 are preferably concave mirrors, the curvatures of the third cavity mirror 503 and the fourth cavity mirror 504 are preferably -100 mm, the distance between the third cavity mirror 503 and the fourth cavity mirror 504 is preferably 100-110 mm, and the second crystal 507 is preferably arranged at the midpoint of the line connecting the third cavity mirror 503 and the fourth cavity mirror 504, so that the second crystal 507 is located at the beam waist position between the third cavity mirror 503 and the fourth cavity mirror 504 in the laser oscillation structure 5, so as to improve the frequency doubling efficiency.

[0107] When the narrow linewidth ultraviolet laser of the present invention in the above embodiment is used, the basic application is the same as that of embodiments 1 to 3, and specifically, further includes: Figure 14-19 As shown, the pump light beam formed outside the laser oscillation structure 5 enters the laser oscillation structure 5 through the first cavity mirror 501 and / or the second cavity mirror 502 for transmission, and the first crystal 506 is single-ended (such as Fig.14 , Fig.16 and Fig.18 as shown) or double ended (as Fig.15 , Fig.17 and Fig.19 As shown) pump, wherein a double-ended pump is preferred, that is: Fig.15 , Fig.17 and Fig.19As shown, the pump light beam is simultaneously enhanced through the first cavity mirror 501 and the second cavity mirror 502 to enter the laser oscillation structure 5 to perform double-end pumping on the first crystal 506; the pump light is absorbed by the first crystal 506 and a fundamental frequency laser is generated; the generated fundamental frequency laser is highly reflected by the first cavity mirror 501 and the second cavity mirror 502 respectively, wherein the fundamental frequency laser reflected by the first cavity mirror 501 enters the second crystal 507 after being highly reflected by the fourth cavity mirror 504, and the fundamental frequency laser reflected by the second cavity mirror 502 enters the second crystal 507 after being narrowed by the FP etalon 508, highly reflected by the third cavity mirror 503, and jointly acted by the polarization element 509 and the isolation element 510; the fundamental frequency laser is then absorbed by the second crystal 507 and a frequency-doubled laser is generated, i.e., a target narrow-linewidth ultraviolet laser; finally, the frequency-doubled laser is enhanced through the fourth cavity mirror 504 and output, i.e., a target narrow-linewidth ultraviolet laser with a wavelength of 261 nm is output.

[0108] In the above application process, the wavelength of the pump light is 444±1nm, the wavelength of the frequency-doubled laser, i.e., the target ultraviolet laser, is 261nm, and the wavelength of the fundamental frequency laser is 522nm; the first crystal 506 is any one of a Pr:YLF crystal, a Pr:LLF crystal, and a Pr:GdLiF crystal; the second crystal 507 is any one of a BBO crystal, a CLBO crystal, a PP-LBGO crystal, a KABO crystal, a KBBF crystal, and a RBBF crystal; in the laser oscillation structure 5 with a ring cavity structure, a unidirectional ring laser oscillation optical path is formed, i.e., the fundamental frequency laser in the above application process oscillates unidirectionally along the ring optical path, and the frequency-doubled laser is generated through the second crystal and output by the output mirror, thereby effectively ensuring the efficient generation and output of the target narrow-linewidth ultraviolet laser, i.e., a narrow-linewidth ultraviolet laser with a wavelength of 261nm.

[0109] In the above application process, in the laser oscillation structure 5, the direction of transmitting the laser from the third cavity mirror 503 to the fourth cavity mirror 504 is taken as the forward direction, and the direction of transmitting the laser from the fourth cavity mirror 504 to the third cavity mirror 503 is taken as the reverse direction, so as to form a unidirectional ring laser oscillation optical path, the laser running in the reverse direction is prevented from continuing to oscillate and transmit through the combination of the isolation element 510 and the polarization element 509; specifically, the process of the isolation element 510 and the polarization element 509 preventing the laser running in the reverse direction is as follows: based on the isolation element 510 including the Faraday rotator 51001 and the half-wave plate element 51002; the laser running in the reverse direction is polarized by the polarization element 509; The S polarized light and the P polarized light are obtained by vibration, wherein the P polarized light is enhanced by the polarization element 509, and the S polarized light is highly reflected by the polarization element 509, and the S polarized light after high reflection is successively rotated by the half-wave plate element 51002 and the Faraday rotator 51001 to become polarized light in the same direction as the P polarized light, and then transmitted through the polarization element 509, thereby realizing the increase of the cavity loss of the laser running in the reverse direction, thereby providing a guarantee for realizing the unidirectional oscillation operation of the laser in the cavity, i.e., forming a unidirectional ring laser oscillation optical path, and then effectively suppressing the spatial hole burning effect, so as to ensure the efficient generation and single-frequency output of the narrow-linewidth ultraviolet laser of the frequency-doubled laser target, i.e., the narrow-linewidth ultraviolet laser with a wavelength of 261nm.

[0110] Example 6

[0111] like Figure 20-25 As shown, a narrow line width ultraviolet laser of the present invention has the same basic structure and application as that of Example 5, except that: Figure 20-25 As shown, in the laser oscillation structure 5, the polarization element 509 is a polarizer.

[0112] In the above embodiment, in order to efficiently obtain the target narrow-linewidth ultraviolet laser, preferably, the polarization element 509 is a polarizer for fundamental frequency laser; the polarization element 509 is coated with a high-reflection film and an anti-reflection film. Preferably, the polarization element 509 is a polarizer for a fundamental frequency laser with a wavelength of 522nm. The fundamental frequency laser generates S-polarized light and P-polarized light with a wavelength of 522nm after being polarized by the polarization element 509. More preferably, the coating angle of the polarization element 509 is 45° or 55.6°. Preferably, the polarization element 509 is coated with a 55.6°522nm S-polarized light high-reflection film and a 55.6°522nm P-polarized light anti-reflection film (i.e., 55.6°HR@522nmS light & 55.6°HT@522nmP light). Thus, the polarization element 509 can achieve high reflection of S-polarized light with a wavelength of 522nm and anti-reflection of P-polarized light with a wavelength of 522nm, and on the polarization element 509, the incident angle and reflection angle of the S-polarized light with a wavelength of 522nm and the P-polarized light with a wavelength of 522nm are both 55.6°.

[0113] In general, it can be seen from the above embodiments of the present invention that, compared with existing narrow-linewidth ultraviolet lasers, the present invention adopts an innovative ring cavity structure design to make the overall volume of the laser more miniaturized, and can effectively improve the efficiency of narrow-linewidth ultraviolet laser output, enhance operational stability, and is more suitable for applications in fields with high precision requirements. In particular, the present invention is compared with the all-solid-state narrow-linewidth ultraviolet laser which is widely used in the prior art and mainly provides a narrow-linewidth ultraviolet laser with a wavelength of 266nm. The narrow-linewidth ultraviolet laser provided by the present invention has outstanding advantages such as small size, light weight, compact structure, and high conversion efficiency. In particular, the former is usually a laser based on Nd-doped crystals, and it needs to undergo two nonlinear frequency conversions from a pump light with a wavelength of 1064nm to a narrow-linewidth ultraviolet laser with a wavelength of 266nm, which makes the structure of the laser complex, and thus makes its application operation relatively complex and difficult. In addition, when the present invention uses a 444±1nm blue light LD as a pump source, it also has the advantages of significantly reducing costs, simplifying structures, and reducing volumes. Moreover, the present invention uses a Pr-doped laser with no obvious thermal effect and high conversion efficiency. 3+When fluoride is a laser crystal, the emission wavelength in the visible light range is 522nm, which enables the present invention to obtain the target narrow-linewidth ultraviolet laser output only after one nonlinear frequency conversion, thereby further simplifying the structure of the laser and reducing the volume of the laser; in particular, the laser oscillation structure of the present invention adopts a ring cavity structure, which can greatly improve the output stability, and use a unidirectional ring oscillation optical path to generate and output the target narrow-linewidth ultraviolet laser, realizing single-frequency output, so that the narrow-linewidth ultraviolet laser of the present invention can be more suitable for fields with high requirements for wavelength accuracy. In short, the miniaturized narrow-linewidth ultraviolet laser provided by the present invention pioneered the provision of a narrow-linewidth ultraviolet laser with a shorter wavelength, that is, a narrow-linewidth ultraviolet laser with a wavelength of 261nm, which is more conducive to energy concentration and improves resolution, and is suitable for promotion and application in fields with high requirements for wavelength accuracy, such as fluorescence absorption, Raman spectroscopy, gene detection, biochemical engineering, space optical communication, and medical treatment.

[0114] The present invention is not limited to the above-mentioned embodiments, and any obvious improvements or changes to the above-mentioned embodiments made by those skilled in the art will not exceed the concept of the present invention and the protection scope of the appended claims.

Claims

1. A narrow linewidth ultraviolet laser, characterized in that: It includes a pump source and a laser oscillation structure, wherein: The pump source is used to provide pump light for the laser oscillation structure; The laser oscillation structure includes a crystal and a resonant cavity, which are used to absorb the pump light and generate ultraviolet laser; The resonant cavity of the laser oscillation structure is a ring cavity structure, and a unidirectional ring laser oscillation optical path is formed in the laser oscillation structure for outputting narrow line width ultraviolet laser; The wavelength of the narrow linewidth ultraviolet laser is 261nm; The laser oscillation structure includes a resonant cavity which is a three-mirror ring cavity structure. The three-mirror annular cavity structure includes a cavity mirror, an FP etalon, an isolation element, and an output mirror, wherein: The laparoscopes have three groups, namely a first laparoscope, a second laparoscope and a third laparoscope; The first crystal is disposed between the first cavity mirror and the second cavity mirror; The second crystal is arranged between the third cavity mirror and the output mirror; The output mirror is arranged between the second crystal and the second cavity mirror; The FP etalon and the isolation element are sequentially arranged between the first cavity mirror and the third cavity mirror; or The laser oscillation structure includes a resonant cavity which is a four-mirror ring cavity structure. The four-mirror annular cavity structure includes a cavity mirror, an FP etalon, an isolation element, and a polarization element, wherein: The laparoscopes have four groups, namely a first laparoscope, a second laparoscope, a third laparoscope and a fourth laparoscope; The first crystal is disposed between the first cavity mirror and the second cavity mirror; The second crystal is arranged between the third cavity mirror and the fourth cavity mirror; The FP etalon is disposed between the second cavity mirror and the third cavity mirror; The polarization element and the isolation element are sequentially arranged between the third cavity mirror and the second crystal.

2. The narrow linewidth ultraviolet laser according to claim 1, characterized in that: The laser oscillation structure includes two groups of crystals, namely a first crystal and a second crystal; the first crystal is used to absorb the pump light and generate a fundamental frequency laser; the second crystal is used to perform frequency conversion on the fundamental frequency laser and generate a frequency-doubled laser; The pump source has two groups, namely a first pump source and a second pump source; the first pump source and the second pump source are respectively located at two sides of the laser oscillation structure; the first pump source and the second pump source respectively provide pump light for the first crystal.

3. The narrow linewidth ultraviolet laser according to claim 1, characterized in that: The first crystal is arranged at the midpoint of the line connecting the first cavity mirror and the second cavity mirror; The third laparoscope is arranged on the perpendicular midline of the line connecting the first laparoscope and the second laparoscope.

4. The narrow linewidth ultraviolet laser according to claim 1, characterized in that: The coating angles of the first cavity mirror and the second cavity mirror are the same; The coating angle of the third cavity mirror is set according to the following formula (1): In the formula, θ1 is the coating angle of the first cavity mirror and the second cavity mirror; θ2 is the coating angle of the third cavity mirror.

5. The narrow linewidth ultraviolet laser according to claim 4, characterized in that: The mutual distances among the first cavity mirror, the second cavity mirror and the third cavity mirror are set according to the following formula (2): In the formula, L1 is the distance between the first laparoscope and the second laparoscope; L2 is the distance between the second cavity mirror and the third cavity mirror; L3 is the distance between the first cavity mirror and the third cavity mirror.

6. The narrow linewidth ultraviolet laser according to claim 1, characterized in that: The first crystal is arranged at the midpoint of the line connecting the first cavity mirror and the second cavity mirror; The second crystal is arranged at the midpoint of the line connecting the third cavity mirror and the fourth cavity mirror; The distance between the first cavity mirror and the fourth cavity mirror is equal to the distance between the second cavity mirror and the third cavity mirror.

7. The narrow linewidth ultraviolet laser according to claim 1, characterized in that: The coating angles of the first cavity mirror, the second cavity mirror, the third cavity mirror and the fourth cavity mirror are the same.

8. The narrow linewidth ultraviolet laser according to claim 7, characterized in that: The mutual distances between the first cavity mirror, the second cavity mirror, the third cavity mirror and the fourth cavity mirror are set according to the following formula (3): In the formula, L1 is the distance between the first laparoscope and the second laparoscope; L2 is the distance between the second cavity mirror and the third cavity mirror; L3 is the distance between the third cavity mirror and the fourth cavity mirror; L4 is the distance between the first laparoscope and the fourth laparoscope; θ is the coating angle of the first cavity mirror, the second cavity mirror, the third cavity mirror and the fourth cavity mirror.

9. The narrow linewidth ultraviolet laser according to any one of claims 1 to 8, characterized in that: The pump source is a semiconductor laser, and the wavelength of the pump light is 444±1nm; The first crystal is any one of a Pr:YLF crystal, a Pr:LLF crystal and a Pr:GdLiF crystal; The second crystal is any one of a BBO crystal, a CLBO crystal, a PP-LBGO crystal, a KABO crystal, a KBBF crystal and a RBBF crystal.

10. The narrow linewidth ultraviolet laser according to any one of claims 1 to 8, characterized in that: The narrow linewidth ultraviolet laser is a single-frequency laser.

Images